Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle diagnosis or maintenance indication
Reexamination Certificate
1999-09-21
2001-10-16
Nguyen, Tan (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle diagnosis or maintenance indication
C701S076000, C340S442000, C303S169000
Reexamination Certificate
active
06304802
ABSTRACT:
FIELD OF THE INVENTION
The invention proceeds from a system for monitoring a condition of the wheels in a motor vehicle.
BACKGROUND OF THE INVENTION
From the state of the art, an anti-blocking control system, an anti-slip control system, a braking force distribution system and a driving dynamic control system are known which control the action of the brakes and/or drives to the individual wheels or individual vehicle axles. An important influence quantity is, inter alia, the rpm of the individual wheels. With a reduction of the diameter of a wheel (for example, by the mounting of a so-called emergency wheel or by a loss in air pressure), erroneous computations which affect safety can occur in such systems because of an incorrect wheel rpm detection. Emergency wheels have, as a rule, a circumference which is up to 25% less than the normal wheels.
From the state of the art, systems for detecting the condition of tires or wheels are known in many variations. Here, of special significance is the detection of a wheel or tire diameter which deviates from the other wheels. Such a deviation can either be caused by a loss in tire air or by a substitute wheel having a deviating diameter, for example, an emergency wheel.
DE-OS 36 30 116 and DE-PS 32 36 520 describe arrangements for indicating the condition of tires of a vehicle wherein the differences of the rotational speeds of individual wheels are determined at specific operating conditions (unbraked, unaccelerated straight-line travel). It is especially suggested to standardize these rotational speeds to the particular vehicle road speed.
A tire tolerance compensation is described in DE-OS 41 13 278 wherein ratios of the rpm speeds of wheels on respective sides of the vehicle are formed in order to compensate the wheel rpms and corrected values for compensating are derived therefrom.
For an anti-blocking control system, a system for detecting an emergency wheel is described in EP,B1,0 449 845 wherein the slip values of the wheels are determined from the wheel rotational speeds and the estimated vehicle road speed (reference speed). If a slip value increases above a threshold value for a specific time duration, then the presence of an emergency wheel is detected and the anti-blocking controller is switched off.
SUMMARY OF THE INVENTION
The object of the present invention is to optimize the detection of the condition of the wheel or tire.
As already mentioned, the invention proceeds from a system for detecting a condition of the wheels of a motor vehicle. For this purpose, means are provided for generating rpm signals which represent the rotational movements of the wheels and evaluation means by means of which a signal is outputted in dependence upon the generated signals and which signal represents the condition relevant for display. The essence of the invention is to configure the evaluation means in such a way that first, and in dependence upon the generated rpm signals, first difference values for the rpm differences of at least two vehicle wheels on the two vehicle sides are formed. The signal, which represents a condition relevant for display, is outputted in dependence upon a first comparison of the formed difference values to pregiven first threshold values.
With the invention, one achieves a very simple and cost-effective wheel condition detection which also operates correctly during curve travel of the vehicle. It is especially provided that it is recognized as a condition of the wheels whether a wheel has a lesser diameter than the remaining wheels (emergency wheel detection) and/or whether a loss of air has occurred in a wheel (tire air loss detection).
It is especially provided that the first difference values, which are formed for each side of the vehicle, are each compared to pregiven first threshold values and the signal is then outputted when the first difference value of the one vehicle side exceeds a first threshold value and the first difference value of the other vehicle side drops below a first threshold value.
It can be further provided that, in dependence upon the generated rpm signals, second difference values for the rpm differences of at least two vehicle wheels in the rearward and forward vehicle areas are formed. The signal, which represents a condition relevant for display, is only outputted when the difference of the second difference values is located within a band determined by pregivable second threshold values. One obtains a reliable and precise detection of an emergency wheel which is present from the check as to whether the difference of the second difference values lies within a specific band.
Whereas the embodiments described until now can only indicate whether a condition of the wheel or tire is present which is relevant for display, it can be determined with the following supplement which of the monitored wheels has a condition relevant to display.
For this purpose, the signal is also dependent upon a third comparison of the individual rpm signals of the wheels on the right vehicle side and on the left vehicle side. Furthermore, the signal is dependent upon a fourth comparison of the second difference values (rpm differences of two vehicle wheels on the two vehicle sides) to each other.
In an especially advantageous configuration of the invention, it is provided that the signal, which represents a display-relevant condition, is only outputted when the display-relevant condition is detected for a pregiven time duration. That is, depending upon requirement, a time-dependent filtering is provided.
For systems which have only a single sensor for detecting the rpm of the rearward wheels, it is provided that the signal is outputted when the formed first difference values both exceed a pregiven third threshold value.
The first, second and/or third threshold values are pregiven especially in dependence upon a value which represents the vehicle longitudinal speed.
Display means are especially provided by means of which a condition, which is relevant for display, is brought to the attention of the driver of the vehicle by driving the display means with the signal. Alternatively, or as a supplement, braking control systems and/or drive control systems are provided whose operating state is changed in dependence upon the outputted signal.
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Berger Walter
Pfau Martin
Stuible Ewald
Nguyen Tan
Ottesen Walter
Robert & Bosch GmbH
Tran Dale Na
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