EP1732772A1

EP1732772A1 - Tire sensitivity recognition method

Info

Publication number: EP1732772A1
Application number: EP05731705A
Authority: EP
Inventors: Martin Griesser; Andreas Köbe; Frank Edling; Vladimir Koukes
Original assignee: Continental Teves AG and Co OHG
Current assignee: Continental Teves AG and Co OHG
Priority date: 2004-04-07
Filing date: 2005-04-01
Publication date: 2006-12-20
Also published as: DE112005000739A5; US20070283750A1; WO2005097525A1

Abstract

Disclosed is a tire sensitivity recognition method comprising the following steps: the tire load FReifen of the vehicle is determined; rotational speed data of the wheels is determined; and the tire sensitivity is determined from the change in the rotational speed data of the wheels in accordance with the change in the tire load FReifen. The invention further relates to the use of said method in a tire pressure monitoring system and a computer program product.

Description

Process for the detection of tire sensitivity

The invention relates to a method for detecting tire sensitivity according to claim 1 and a computer program product according to claim 11.

A reliable monitoring of the tire air pressure on all wheels of a motor vehicle or a motorcycle is of great importance for the safety of the vehicle. A so-called indirectly measuring tire pressure monitoring system (eg DDS: Deflation Detection System) is known from DE 100 58 140 AI, which detects an air pressure loss on the wheels on the basis of wheel speed information, such as the rolling circumferences.

It has been shown that tire sensitivity, i.e. H. the change in the tire roll due to a loss of tire pressure is different for different types of tires. This can lead to false warnings or no warnings from the indirectly measuring tire pressure monitoring system.

The object of the present invention is to provide a method for detecting tire sensitivity.

This object is achieved by the method according to claim 1.

Further features of the invention result from the subclaims and the following description with reference to figures. Here show:

1 shows a first flow chart,

2 shows a second flow chart, and 3 shows the lateral acceleration a _lat over a time quotient

The dependence of the dynamic rolling radius ΔR _c i _yn as a function of the air pressure loss Δp differs widely between different tire sets. In indirectly measuring tire pressure monitoring systems (DDS: Deflation Detection System), the change in the dynamic rolling circumference ΔR _d y _{n is used} as an indicator of a tire pressure loss. If a fixed warning threshold is used for a specific change in the dynamic rolling radius for an indirectly measuring tire pressure system, a warning is given regarding an air pressure loss for different tire types at different tire pressure levels.

In order to adapt the warning thresholds to the type of tire currently mounted on the vehicle, the dependence, hereinafter referred to as tire sensitivity, of the dynamic rolling radius ΔR-iy _n as a function of the air pressure loss Δp for this type of tire must be known. For this purpose, the method according to the invention determines the tire sensitivity of a type of tire currently mounted on a vehicle.

Two methods (method 1 and method 2) are proposed for determining tire sensitivity.

In method 1, the physical effect is measured using wheel speed sensors to determine tire sensitivity. There are two effects that determine tire sensitivity:

Effect 1.1: Tire contact area growth: the greater the relative growth of the tire contact area in longitudinal The direction of a tire depends on the loss of air pressure, the greater the sensitivity of the tire.

Effect 1.2: Wheel torque dependency: the "softer" a tire is (e.g. the rubber compound is softer with winter tires than with summer tires), the more the tire sensitivity decreases depending on the wheel torque. Example: a winter tire has almost the same tire sensitivity at low wheel torques like a summer tire, but it is much less sensitive to higher wheel torques.

By evaluating effect 1.1, a basic warning threshold is set depending on the sensitivity of the tire. Effect 1.2 is evaluated in order to achieve a more accurate detection of soft tires, which reduces a warning threshold at high wheel drive torques.

First the tire sensitivity is determined depending on the growth of the tire contact patch (effect 1.1). If the air pressure of a tire drops, the tire footprint and thus the dynamic rolling circumference change depending on the tire sensitivity. The change in the dynamic rolling circumference is recognized by the indirectly measuring tire pressure monitoring system and a warning is given regarding an air pressure loss.

Another variable that causes the tire contact area to grow is the tire load tire. The greater the tire load F _Re if _e n, the larger the tire contact area. A force signal from an active chassis system can be used as an indicator of the tire load. If there is no such signal, the tire load must be estimated. For this, the current cross acceleration aι _at , which is present, for example, as an input signal to an electronic stability program (ESP), is used to estimate the change in tire load.

The tire load F _Re ifen is estimated from the lateral acceleration aι _at with the help of a vehicle model. The tire load on tires leads to a change in the dynamic rolling circumference. This can be determined by means of the speed measured with wheel speed sensors. This relationship (change in tire load - change in dynamic rolling circumference) is used to determine tire sensitivity.

A lateral acceleration aι _at the vehicle, for example, caused by a cornering, in which the bend-outward wheels are more heavily loaded than the inside wheels, whereby said tire load FR _eifen the outer wheels increases while the tire load F _Relfen decreases the 'inside wheels. The influence of the lateral acceleration aι _{at is} determined by comparing the wheel speeds ω on an axis. For this purpose, the distribution of the tire load for the left (F _Re ien-ii-ιs) and for the right (F _Re ifen-right) wheel is calculated from the lateral acceleration aχ _at using a vehicle model 1 (see FIG. 1). By changing or shifting the tire loads (FR _e if _en -iinks and Feifen-echs) when cornering, the dynamic rolling circumference of the bend inside and outside bends (-ΔR _dyn and + ΔR _dyrι , represented by reference number 2 ), which also results in a change in the wheel speeds (+ Δω and -Δω) of the respective wheels (represented by reference number 3). An indirectly measuring tire pressure monitoring system measures and evaluates the wheel speed diche or dependent sizes, such as. B. the cycle times to detect an air pressure loss. If there is a change in the wheel speeds due to a lateral acceleration, this is also reflected in the evaluation of an indirectly measuring tire pressure monitoring system (represented by reference number 4). For example, are times from the indirectly measuring tire pressure monitoring system, e.g. B. a certain number of pulses from the encoder wheel a wheel speed sensor, detects, as input variables, the variation of these periods (delta T _rec --ts and ΔTii + _NCP) are determined for the respective wheel. If a quotient (ΔT _right / ΔTι _inks ) from the changes in times (-ΔT _reC hts and + ΔTunks) is determined and this is plotted against the lateral acceleration aι _at , regression lines 7, 8 result as shown in FIG. 3 , The slope of this regression line 7, 8 describes the tire sensitivity of the tires on the axis under consideration. If you perform the above calculation for all axles, or for all wheels arranged on the axles, you get an individual tire sensitivity of the wheels on the axle under consideration.

During cornering, ΔT _rech ts / ΔTii _n ks is not only influenced by the tire load, but the cornering radius itself is the largest influencing factor that must be compensated for.

It is possible to calculate the curve radius from the yaw rate and the vehicle speed. The flow diagram for this is shown in FIG. 2. . Which a ratio 5 (.DELTA.T / ΔTii _nk _right) is formed _in, Figure 2 differs from the flowchart in Figure 1 in that from the changes of the times. (I _nk delta T _{computationally} t _s and + .DELTA.T. ₁₎ a compensation step 6 with the influence of the curve radius or with the Yaw rate is compensated. One embodiment of the compensation step is to subtract the compensation value K from the quotient 5. K is calculated as follows, where ψ is the yaw rate, S is the track width and v _rej - the speed of the vehicle.

K ^■ * - = k ^K kσmp - ^ ^V ref

The constant c _fom is used to correctly scale the compensation value.

This results in the slope of the regression line 7, 8 as shown in FIG. 3. Here, the regression line 7 shows the typical behavior (large slope) of a sensitive tire, whereas the regression line 8 shows the typical behavior (lower slope) of an insensitive tire. It is recommended to use this procedure depending on the wheel torque, e.g. B. in wheel torque intervals to apply.

Measurements have shown that the above method can only be used if it is known whether a summer or a winter tire is fitted to the vehicle, since an insensitive winter tire can have an almost equal slope of the regression line as a sensitive summer tire. Nevertheless, this method can be used until it is possible to determine the tire stiffness depending on the wheel moments (effect 1.2).

If, instead of the wheels on an axle, the wheels on a vehicle side (“sample side”) are alternatively considered as a function of the lateral acceleration, this results in an average tire sensitivity of all wheels. If the forces of the diagonal wheel positions are structured very differently, then it is also possible to use the diagonally arranged wheels (“sample diag”) for the evaluation.

In the following example, assume that the change in the force on the front axle depending on the transverse bescϊileunigung _iat a assumes the value zero, and is present only at the rear axle, a change of the force. Then the scanning times ΔTi, ΔT _{2 of} the front axle have no effect on the calculation and sample diag = (T1 + T3) / (T2 + T4) - 1 can be used in the same way as ΔTrechts / ΔTunks • This assumption leads to a solution if the power shifts are very different, for example with a heavy front engine and low rear loading.

As long as the force at any wheel position on a large scale a _iat varies depending on the lateral acceleration, the -bevorzugte assumption:

.DELTA.T _r ight / _NCP ΔTιi = f (aχ _a)

If another measurable physical effect apart from the loss of air pressure is found, which increases the tire contact area, and the dynamic rolling radius can be determined at the same time, the function ΔR _d yn = f (effect) can also be used to determine the tire sensitivity.

In the following, the evaluation of the wheel torque dependency of the tire sensitivity (effect 1.2) is considered in more detail. As I said earlier, the soft tires show a reduction in tire sensitivity depending on the wheel torque.

With the indirectly measuring tire pressure monitoring system (DDS) it is possible to use the slope of the learned axle references (SAMPLE AXLE) above the wheel torque to determine the tire rigidity.

SAMPLE AXLE = (Tι + T ₂ ) / (T ₃ + T ₄ ) - 1 (1)

The axis reference (SAMPLE AXLE) depends on the slip. The following applies to vehicles with front-wheel drive:

SAMPLE AXLE = SAMPLE AXLE ₀ - k * λ (2)

The following applies to vehicles with rear-wheel drive:

SAMPLE AXLE = SAMPLE AXLE ₀ + k * λ (3)

with SAMPLE AXLE ₀ : initial value of the SAMPLE AXLE value when the wheel torque is almost "0"; k: coefficient of proportionality; X: slip

The slip is proportional to the wheel torque Tq:

λ = ki * Tq, (4)

k _x : proportionality coefficient between wheel slip λ and wheel torque Tq.

Therefore, the following applies to front-wheel drive vehicles:

SAMPLE AXLE = SAMPLE AXLE ₀ - k ₂ * Tq (5) and for rear-wheel drive vehicles:

SAMPLE AXLE = SAMPLE AXLE ₀ + k ₂ * Tq (6)

with k ₂ = k * k _x

The coefficient of proportionality k ₂ is the slope of the line dependency (equation (4) or (5)). This slope is proportional to the adhesion coefficient:

k ₂ = μ * k ₃ (7)

From equations (4) to (7) it follows:

for f-tront driven vehicles:

SAMPLE AXLE = SAMPLE AXLE ₀ - k ₃ * μ * Tq (8)

and for rear-wheel drive vehicles:

SAMPLE AXLE = SAMPLE AXLE ₀ + k ₃ * μ * Tq (9)

The adhesion coefficient μ depends on the rigidity of the tire on the road surface. The coefficient of adhesion is greater, the lower the tire rigidity. This means that the slope of the straight line (equation (7) or (8)) is larger for softer tires than for stiff tires. The influence of the road properties is usually much less than the influence of the tire rigidity.

As it turned out, so-called wide tires are more rigid than narrow tires, and summer tires have greater stiffness than winter tires. It has also been shown that the stiffer the tires, the greater the effective change in tire roll circumference due to a loss of air pressure. This change is larger for wide tires than for narrow tires. It is larger for summer tires than for winter tires. These findings are used to set the detection thresholds of the indirectly measuring tire pressure monitoring system (DDS) and to determine the tire properties.

For this, the axis reference "SAMPLE AXLE ^Λ is learned first.

For learning, pairs of values are formed from the values "SAMPLE AXLE" and the wheel moments Tq. The regression line (equation

(5) or (6)) calculated. The learning is only ended when the regression line has a high correlation coefficient. The learned values k ₂ and SAMPLE AXLEo are saved. It is recommended that this learning process taking into account the vehicle speed, e.g. B. in speed intervals to perform.

The warning thresholds of the indirectly measuring tire pressure monitoring system (DDS) are then adjusted. The greater the slope | k ₂ 1 of the regression line (equation (5) or

(6)), the smaller the change in the actual tire circumference in the event of a loss of air pressure. If the slope is large, the warning thresholds are reduced. A particularly low tire sensitivity on the driven axle is required for high wheel torques. If the gradient is low, the warning thresholds for high wheel torques are reduced less. The information about the tire rigidity can also be made available to other vehicle systems (e.g. ABS or ESP) in order to improve control algorithms.

In method 2, the tire properties are determined directly from tire information or tire data that are stored in the tire. The tire information is stored, for example, in a transponder which is arranged in or on the tire. This tire information is transmitted to a control unit in the vehicle. The tire information can e.g. B. during the manufacture of the tire or during assembly of the tire in a workshop in the transponder. It is also possible for the driver to specify the tire information or to select it from a list of tire types stored in the control unit. Furthermore, the tire information can also be derived from other vehicle components used, such as engine and brake data.

With this "transponder technology" it will be possible in future to store the tire data encrypted in the tire during production. By means of activation and reception antennas on the vehicle, the transponder in the tire can be activated from the vehicle so that it transmits its information and this can in turn be received by the vehicle and forwarded to a control unit.

With the emerging transponder technology, it will be possible to send stored parameters in the tire, e.g. the tire stiffness or the tire size (e.g. Continental Sport Contact 225 / 45R18), to a control unit, which includes an indirect measuring tire pressure monitoring system (DDS) , The control unit assigns a list of Tires and tire sensitivities from which the desired warning thresholds can be read out.

Another method could be to write the tire data to the control unit at the end of production. Every time the tire is changed in the workshop, the tire information must be updated, for example using diagnostic test tools.

A third approach for the market of technically experienced drivers (e.g. high-performance sports cars like the BMW M-Series) is to let the driver enter the tire data himself using a device on the dashboard.

A fourth method is to derive the maximum tire size from the data of the brake discs and / or the engine data in the vehicle. Many manufacturers do not offer the largest tire sizes for vehicles with a low engine output. The system can therefore be adapted to narrow tires if the engine governor provides relevant information. If the brake disc information is stored in the control unit, the minimum rim size is known because the rim must be larger than the brake disc. By combining this information into a list of the manufacturer about the tire / engine combinations, it is possible to estimate the range of possible tires mounted on the vehicle in order to set the warning thresholds.

Claims

claims:

1. A method for detecting the tire sensitivity, characterized by the steps of: determining the tire load F _R eif n _e of the vehicle, detecting wheel speed of the wheels, determining the tire sensitivity of the change in the wheel speed dependent on the change of the tire load outdoors-

2. The method according to claim 1, characterized in that the tire load F _{Rei e} ιι from a tire load sensor system or from another chassis sensor system, as z. B. is available for active trolleys is determined.

3. The method according to claim 1, characterized in that the tire load F _Re i _e n is determined from the lateral acceleration a _{iat of} the vehicle.

4. The method according to claim 3, characterized in that the lateral acceleration a ^ is measured by means of a lateral acceleration sensor.

5. The method according to claim 1, characterized in that the wheel speed information (wheel revolution time, wheel speed, wheel roll circumference, etc.) of the wheels is determined by means of wheel speed sensors.

6. The method according to claim 1, characterized in that the determination of the tire sensitivity is carried out taking into account or compensating for the radius of the curve.

7. The method according to claim β, characterized in that the curve radius is determined by evaluating the yaw rate and the speed of the vehicle.

8. The method according to claim 1, characterized in that the determination of the tire sensitivity is determined taking into account the wheel moments.

9. Use of the method for detecting the tire sensitivity according to at least one of claims 1 to 8 in an anti-lock braking system (ABS) and / or an electronic stability program (ESP).

10. Use of the method for detecting the tire sensitivity according to at least one of claims 1 to 8 in an indirectly measuring tire pressure monitoring system.

11. Computer program product, characterized in that it defines an algorithm which comprises a method according to claim 1.