Land vehicles – Wheeled – Attachment
Reexamination Certificate
1999-11-24
2001-11-06
Culbreth, Eric (Department: 3611)
Land vehicles
Wheeled
Attachment
C701S045000
Reexamination Certificate
active
06312013
ABSTRACT:
PRIORITY CLAIM
This application is based on and claims the priority under 35 U.S.C. §119 of German Patent Application 198 54 366.2, filed on Nov. 25, 1998, the entire disclosure of which is incorporated herein by reference.
FIELD OF THE INVENTION
The invention relates to a method of updating a trigger threshold of a passive safety system including a passive safety device, such as an air bag or a seat belt tensioner, which is especially for use in a motor vehicle.
BACKGROUND INFORMATION
Devices and methods are known in the art for measuring acceleration-dependent signals that are relevant to the safety of passengers in a vehicle involved in a crash or other sudden impact. Such acceleration-dependent signals, for example, relate to the present instantaneous acceleration of the vehicle, an acceleration integral and/or the change in velocity. Throughout the present specification, the term “acceleration” is understood to refer to or include negative acceleration or deceleration, as is experienced by a vehicle in a crash.
Trigger devices are also known that can trigger safety devices such as airbags and seat belt tensioners in response to and dependent on those acceleration-dependent signals. To determine whether a safety device should be triggered, the value of the particular incoming acceleration-dependent signal is compared to a so-called trigger threshold, that is the threshold value for triggering the device. For example, an acceleration sensor provided in a vehicle outputs a signal that is indicative of the instantaneous acceleration (or deceleration) of the vehicle. If this acceleration signal exceeds the threshold value, then the trigger circuit will activate a triggering device to deploy the respective associated safety device. various types and arrangements of triggering devices and comparator circuits are known in the art, and the details thereof are not pertinent and are not limiting as to the present invention.
It is also known that a trigger device can have an adaptable or adjustable trigger threshold value, as can be seen in the German Patent DE 38 16 591. Therein, the trigger threshold value is adapted to certain sudden crash-like situations, dependent on various determined operating parameters of the vehicle, in order to increase the trigger sensitivity of the restraining means. Particularly, the above mentioned German Patent discloses using the change in velocity as the correction value for changing the trigger threshold value. An optimal adaptation, however, can only be achieved for new motor vehicles, because the above mentioned operating parameters have now been found to vary over time as a vehicle ages.
Throughout this specification, the terms “age”, “aging” and the like are not limited to chronological age, but rather refer to any factor that degrades or deteriorates a motor vehicle, and particularly the chassis or frame of the motor vehicle, from its new condition. Such factors include, without limitation, the chronological age of the vehicle, the total cumulative miles traveled by the vehicle, the total cumulative operating hours of the vehicle, the degree of vibration to which the vehicle has been subjected while operating (e.g. due to traveling on bumpy roads), the degree of rusting of the vehicle frame or body, etc. For example, a vehicle that has been driven a great total cumulative distance under severe conditions (e.g. bumpy unpaved roads, or a number of small accidents or impacts) may be substantially “aged” and deteriorated from its new condition, regardless of its chronological age. Long term tests have shown that, as a vehicle degrades or deteriorates, i.e. “ages” regardless of the cause, the stiffness of the vehicle frame changes significantly as a result of material fatigue, joint fatigue, rust degradation, and the like, especially for some types of vehicles. It has also been shown by tests or investigations, that the existing safety devices such as airbags were not triggered in some cases of frontal impact accidents involving older vehicles, due to the above mentioned aging or degrading influences.
OBJECTS OF THE INVENTION
In view of the above it is an object of the invention to provide a method of operating a passive safety system in a vehicle, so as to enable reliable and consistent triggering of the safety device(s) of the safety system regardless of the vehicle age, i.e. in older or deteriorated vehicles as well as in new vehicles. Particularly, the inventive method aims to take into account one or more degradation-related parameters relating to the degree of degradation or deterioration of the vehicle. It is also an object of the invention to provide a circuit arrangement for carrying out such a method. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification.
SUMMARY OF THE INVENTION
The above objects have been achieved in a method and in a circuit arrangement according to the invention, wherein the trigger threshold is automatically updated as a function of at least one degradation-related parameter of the vehicle. The trigger threshold is updated or changed over time, dependent on this degradation-related parameter, preferably so that the responsiveness of the safety system is not affected by the aging (i.e. degradation) of the vehicle, or at least so that the influence of the aging of the vehicle on the responsiveness of the safety system is partially compensated.
This degradation-related parameter according to the invention may be the chronological age of the vehicle, the cumulative operating time of the vehicle, the total traveled distance of the vehicle, the determined degree of rusting of the vehicle frame or body, the cumulative or integrated vibrations to which the vehicle has been subjected during its operation, the cumulative or integrated acceleration variations that the vehicle has undergone during its operation, the cumulative or integrated engine speed (rpm) of the vehicle's engine during operation, the number of small shocks or impacts suffered by the vehicle (e.g. below a threshold for triggering the safety devices but above a threshold at which degradation of the vehicle structure results), the measured stiffness of the vehicle chassis or frame, or any other factor that is indicative of the actual existing strength and/or stiffness characteristic of the vehicle chassis or frame.
Tests have shown that the characteristic curve of the deceleration as a function of time, of an older vehicle undergoing a collision or other crash impact is significantly different from the corresponding characteristic deceleration curve of a new vehicle undergoing the same crash impact (even if the old and new vehicles are of the same type, class or manufacturer model). Throughout this specification, the term “crash impact” refers to a sudden deceleration of a vehicle, which exceeds a deceleration level that is considered safe or acceptable for passengers of the vehicle. Also, the term “vehicle class” refers to a group of vehicles that share similar characteristics and particularly the same characteristic deceleration curve in a crash test when compared to other vehicles of the same class and the same vehicle age. For example, all cars of a particular manufacturer's model will be within the same class.
The different deceleration curves exhibited by vehicles of the same class but of different ages (i.e. degrees of degradation) result because the stiffness or rigidity of the frame of a vehicle relaxes as the vehicle “ages” as a result of various factors as mentioned above. This is due to degradation of the vehicle frame caused by fatigue and rust, among other things. As a result of this reduced stiffness or rigidity, the rate of decrease in velocity, i.e. the deceleration, of an older vehicle involved in a frontal crash for example, is less pronounced than that of a new vehicle. In other words, the older vehicle is “softer” and “eases into” the crash, in comparison to the newer vehicle which is “stiffer” and therefore decelerates
Baur Richard
Fendt Guenter
Steurer Helmut
Culbreth Eric
Daimler-Chrysler AG
Lum L.
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