DE102010029154A1 - Method for recognizing creeping air pressure loss of tire of motor car, involves determining rolling resistance of tires from force equilibrium of traveling vehicle, and determining unknown parameters in equilibrium of forces equation - Google Patents

Abstract

The method involves determining rolling resistance of tires (2) from force equilibrium of a traveling vehicle (1). Unknown parameters in the equilibrium of force equation are determined by using a statistical-numerical estimation process. The average resistance value over a set of travels is determined to reduce environment and road influences. Air resistance of the vehicle is determined to be supplementary to the tire resistance from the force equilibrium. A creeping tire pressure loss is recognized in an indirect measuring tire pressure control system. An independent claim is also included for a motor car control apparatus.

Description

The invention relates to a method according to the preamble of claim 1 and a motor vehicle control unit according to claim 13.

In many motor vehicles, tire pressure monitoring systems ensure increased safety when driving. However, monitoring tire pressure in the tires not only provides a safety benefit, but properly adjusted tire inflation pressure also results in increased ride comfort and avoids increased rolling resistance, thus helping to save both fuel and CO ₂ .

In the current discussion particularly direct measuring systems (TPMS), such as. B. in the DE 102 43 913 A1 described with regard to the determination of fuel consumption and the associated CO ₂ emissions considered advantageous because they can reliably detect even low reduced pressures. In addition, so far only these comparatively expensive, direct measuring systems are able to creep and uniform in all tire pressure loss z. B. to recognize due to always present in all tires diffusion effects.

Indirectly measuring systems (DDS) do not yet achieve the accuracy of a direct-measuring system, but are much more cost-effective, since these indirectly measuring systems on already mounted in the vehicle sensors such as the tachometer of an ABS or ESP system on the vehicle wheels , can access. However, these are so far not able to detect a uniform pressure loss of all mounted on the vehicle tires, since only the wheel data of the individual tires are relatively compared. Examples of indirectly measuring systems are approximately in DE 101 29 737 A1 and DE 199 59 554 A1 given.

Even a slight reduction of 0.3 bar is sufficient z. B. to cause a 6% increase in rolling resistance. As a result, both the fuel consumption and the CO ₂ emissions increase unnecessarily.

There is therefore a need for an improved, cost-effective, indirect measurement method for detecting a creeping and uniform tire pressure loss of all tires at the same time z. B. by diffusion effects.

This object is achieved by the method according to claim 1 and by the motor vehicle control unit according to claim 13.

The inventive method for detecting a creeping air pressure loss of a tire of a motor vehicle is characterized in that in the recognition of the rolling resistance of the tire is taken into account. The advantage of this method is that a tire condition is directly observed here, which depends directly on the tire pressure. In this way, it is therefore possible even low and uniform pressure losses, eg. B. by diffusion, reliable to recognize. By considering the rolling resistance, an exact detection of only minimal pressure losses is possible, as they consistently make a noticeable increase in rolling resistance.

Preferably, the rolling resistance is determined from the equilibrium of forces of a moving vehicle. This approach takes into account the sum of the forces acting on the vehicle and thus also allows an accurate determination of rolling resistance.

The equilibrium of forces is preferably formed by an equation which links directly accessible and indirectly accessible parameters. The indirectly accessible parameters can preferably be determined by means of a statistical-numerical parameter estimation method (so-called "Moment Method", Rainer Schlittgen: Introduction to Statistics, pp. 288-289 . Oldenbourg Wissenschaftsverlag, Oldenbourg 2008, ISBN 3-486-27446-5 ) reliably determine. The moment method is a method of statistical mathematics in which as many measurements as possible estimate the theoretical distribution of a population.

It is preferably assumed that the sum of the individual forces acting on the vehicle is equal to the total force to be applied by the engine. Individual partial forces can also have the same direction of action as the engine power. This can be represented by the sign of the partial force.

Advantageously, to determine the rolling resistance on the data provided by an indirectly measuring tire pressure monitoring system and / or brake system and / or vehicle control system available data. As a result, it is not necessary to integrate additional sensors in the vehicle, which would be associated with additional costs.

In a further preferred embodiment of the invention, the determined rolling resistance is averaged over several trips in order to reduce environmental and road influences. This procedure allows a reliable and precise recognition of the Rolling resistance, regardless of constantly changing disturbing influences.

Preferably, increased by an increased rolling resistance fuel consumption and thereby also increased CO ₂ emissions are determined.

In particular, the driver may receive an indication of increased fuel consumption and CO ₂ emissions due to increased rolling resistance. Thus, the driver can correct the filling condition of the tires and reduce the fuel consumption and CO ₂ emissions.

Expediently, in addition to the rolling resistance of the tires, the drag coefficient of the vehicle is determined from the equilibrium of forces of a moving vehicle. About the drag coefficient can be such. B. are recognized, for example, if a roof rack or other structures are mounted.

Particular preference is also given to increasing fuel consumption, which is increased by increased air resistance, and thereby likewise increasing CO ₂ emissions.

In particular, the driver may receive an indication of increased fuel consumption and CO ₂ emissions due to increased rolling resistance. Thus, the driver can possibly eliminate the cause of the increased drag coefficient and reduce fuel consumption and CO ₂ emissions.

Conveniently, a suitable indication indicates the potential for savings in terms of fuel consumption and / or CO ₂ emissions in eliminating the cause of the increased rolling resistance and / or air resistance. The driver can thus be made accurate information about the amount of unnecessary fuel consumption and savings.

Advantageously, the method is characterized in that in an indirectly measuring tire pressure monitoring system without additional sensors, a uniform, creeping tire pressure loss is detected. This ability was previously only available for much more expensive, directly measuring tire pressure monitoring systems.

The invention further relates to a vehicle control unit, which performs a method for detecting a creeping tire pressure loss of a tire, wherein the motor vehicle control device takes into account the rolling resistance of the tires.

A preferred use of the described method for detecting a creeping air pressure loss of a tire of a motor vehicle is integrated into an indirectly measuring tire pressure control system.

Further preferred embodiments will become apparent from the subclaims and the following description of an embodiment with reference to figures.

Show it

1 on a vehicle ( 1 ) while driving forces and

2 a schematic representation of the method according to the invention.

1 represents a vehicle 1 with wheels 2 The vehicle travels up a slope which has an angle α with respect to the horizontal. The engine of the vehicle applies the force F _ride . The engine power in this example are the acceleration force F _acceleration , the downhill force F _slope , the air resistance F _air and the rolling friction force F _{Roll of} the wheels 2 , If the vehicle is traveling at a constant speed (F _acceleration = 0) then the sum of all these forces is zero.

Likewise, it is of course possible that the vehicle moves down the slope. In this case, the downhill force F _{slope of} the engine power F _{ride is} not opposite but has the same direction of action. Also, the resulting from the air resistance air friction force F _air does not necessarily have to be opposite to the engine power F _ride . It is Z. B. possible that the vehicle moves with tailwind. In these cases, the sign of the corresponding forces of their direction of action is adjusted so that they act depending on the situation against the engine power F _ride or support them.

In 2 is a schematic of a method for determining the tire pressure loss 7 , fuel consumption and related CO ₂ emissions 8th as well as the savings potential of fuel 9 shown. The data or sensors of an indirectly measuring tire pressure monitoring system 3 , the brake control systems 4 and other vehicle control systems 5 be from a motor vehicle control unit 6 used by a statistical-numeric method such. B. the moment method to estimate the parameters needed to solve the balance of power equation or to measure directly.

According to the embodiment, the balance of power equation is determined by the following relationship: F _travel = M _Rad / r _dyn = F _acceleration + F _slope + F _roll + F _air

Where: F _acceleration = m _vehicle · a _abs + (4 · J _wheel + J _red · a _abs ) / r ² _dyn F _slope = m _vehicle · (a _sensor - a _abs ) F = _air c _F · A · ρ · v ^2/2 F _roll = f · m _vehicle · g

m_Fahrzeug

= Masse des Fahrzeugs

M_Rad

= Drehmoment der Räder

a_abs

= von den Radsensoren berechnete Beschleunigung

J_Rad

= Trägheitsmoment der Räder

J_red

= reduziertes Trägheitsmoment des Motors, Getriebes, etc.

r_dyn

= dynamischer Abrollumfang

a_sensor

= gemessene longitudinale Beschleunigung

f

= Rollwiderstandskoeffizient

c_w

= Luftwiderstandsbeiwert

A

= Frontquerschnittsfläche

ρ

= Dichte der Luft

v

= Geschwindigkeit des Fahrzeugs

g

= Erdbeschleunigung

With:

m _vehicle

= Mass of the vehicle

M _wheel

= Torque of the wheels

a _abs

= acceleration calculated by the wheel sensors

J _wheel

= Moment of inertia of the wheels

J _red

= reduced moment of inertia of the engine, transmission, etc.

r _dyn

= dynamic rolling circumference

a _sensor

= measured longitudinal acceleration

f

= Rolling resistance coefficient

c _w

= Drag coefficient

A

= Front cross-sectional area

ρ

= Density of air

v

= Speed of the vehicle

G

= Gravitational acceleration

According to a further embodiment, the directly measurable variables such. B. the engine torque, the speed, the acceleration and other directly measurable parameters detected. By means of the moment method, the quantities of the above equation which are not directly detectable are then estimated.

To resolve the above equation of equilibrium, the torque of the wheels (or the torque of the motor) and the dynamic rolling circumference of the wheels are first provided by a known DDS system. The ABS or ESP system determines the acceleration of the vehicle based on the wheel speed change. Likewise, the vehicle speed can be determined via the wheel speed. Other parameters, such as the vehicle mass, which is usually not detected by a DDS system, can also via the torque method of the vehicle control unit 6 to be appreciated. About the CAN bus of the vehicle, the motor vehicle control unit about every 10 ms a complete set of the measured data is provided. Since the correlations of the measured data are partly significantly influenced by external influences, such. B. a road gradient or the road surface, very quickly creates a large number of sometimes very different estimates for the individual sizes. In the case of the vehicle mass, for example, the estimated values are generally within a Gaussian function. The maximum of the Gaussian function indicates that value which is most likely to correspond to the actual mass. Already after less than 20 journeys, a reliable value for the vehicle mass can already be given with very high accuracy. The determination of other parameters of the equilibrium equation is analogous. The system then determines the current tire pressure from the determined rolling resistance. Although this method, like all indirect measuring systems, does not allow any determination of the absolute pressure, nevertheless a certain deviation from a predefined "zero point" can be reliably detected.

According to another example for carrying out the method, the vehicle may be equipped with an additional longitudinal acceleration sensor, which also measures the acceleration. By comparing the acceleration values measured by the longitudinal acceleration sensor and the wheel speed, it is possible to determine, for example, B. very easily a slope of the road are determined and in turn the corresponding, acting on the vehicle downgrade force. In this case, the number of parameters to be determined by the torque method decreases, which remarkably reduces the time until the existence of reliable estimates.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10243913 A1 [0003]
• DE 10129737 A1 [0004]
• DE 19959554 A1 [0004]

Cited non-patent literature

• "Moments Method", Rainer Schlittgen: Introduction to Statistics, pp. 288-289 [0010]
• Oldenbourg Wissenschaftsverlag, Oldenbourg 2008, ISBN 3-486-27446-5 [0010]

Claims (13)

Method for detecting a creeping air pressure loss of a tire ( 2 ) of a motor vehicle ( 1 ), characterized in that in the recognition of the rolling resistance of the tire is taken into account. A method according to claim 1, characterized in that the rolling resistance from the balance of power of a moving vehicle ( 1 ) is determined. Method according to at least one of claims 1 or 2, characterized in that unknown parameters in the balance of power equation are determined by means of a statistical numerical estimation method. Method according to at least one of claims 1 to 3, characterized in that, for determining the rolling resistance, the pressure to be measured by an indirectly measuring tire pressure monitoring system ( 3 ) and / or brake control system ( 4 ) and / or vehicle control system ( 5 ) provided sensor data is used. Method according to at least one of claims 1 to 4, characterized in that the rolling resistance is averaged over several trips to reduce environmental and road influences. Method according to at least one of claims 1 to 5, characterized in that it is checked whether an increased fuel consumption and thereby also increased CO ₂ emissions is due to an increased rolling resistance. A method according to claim 6, characterized in that the driver receives an indication of increased fuel consumption and CO ₂ emissions due to increased rolling resistance. Method according to at least one of claims 1 to 7, characterized in that in addition to the rolling resistance of the tire, the drag coefficient of the vehicle is determined from the equilibrium of forces of a moving vehicle. Method according to at least one of claims 1 to 8, characterized in that an increased by an increased air resistance fuel consumption and thereby also increased CO ₂ emissions are determined. Method according to at least one of claims 1 to 9, characterized in that the driver receives an indication of increased fuel consumption and CO ₂ emissions due to increased air resistance. Method according to at least one of Claims 1 to 10, characterized in that a suitable indication indicates the saving potential with regard to the fuel consumption and / or CO ₂ emission when the cause of the increased rolling resistance and / or air resistance is eliminated. Method according to at least one of claims 1 to 11, characterized in that in an indirectly measuring tire pressure monitoring system without additional sensors, a uniform, creeping tire pressure loss is detected. Motor vehicle control unit, which performs a method for detecting a creeping tire pressure loss of a tire according to at least one of claims 1 to 12, characterized in that the motor vehicle control unit takes into account the rolling resistance of the tires.

Images