Boots – shoes – and leggings
324162, G01P 1502
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an accelerometer arrangement and more particularly relates to an accelerometer arrangement for use in a motor vehicle.
2. Background Information
An accelerometer may be used in a motor vehicle to measure the deceleration of the motor vehicle. Such an accelerometer may be utilized to trigger a safety device, such as an inflatable air bag, when the deceleration detected by the accelerometer corresponds to accident conditions.
It is important that an air bag is inflated at the correct instant. The reason for this is that an air bag takes a certain period of time to become fully inflated, but once it has inflated it then starts to deflate. It is therefore important that when a person travelling in a motor vehicle is thrown forwardly, in an accident, the air bag should be fully inflated just before the person is thrown forwardly.
It is found that the deceleration curves for a motor vehicle involved in an accident depend very much upon the relative speed of impact. Of course, the rate of forward travel of a person towards an air bag provided in a vehicle also depends upon the speed of the vehicle before the initial impact of the accident, and the actual position of the person (i.e. whether they are leaning forwards, or sitting back) can have an effect.
SUMMARY OF THE INVENTION
Of course, the deceleration curve of any particular vehicle is unique to that design of vehicle, depending upon many factors, including the characteristics of the so-called "crumple zone" which is now usually built into the front part of a motor car. This part of the motor car is designed to crumple during an accident to provide a relatively smooth deceleration of the passenger-containing part of the vehicle.
There is thus a requirement for an accelerometer which is able to provide an output signal to trigger an item such as an air bag in response to deceleration of the vehicle, the signal being provided at the appropriate time depending upon the nature of the deceleration of the vehicle.
The present invention seeks to provide an improved accelerometer arrangement.
According to this invention there is provided an accelerometer arrangement, said arrangement comprising an accelerometer adapted to provide signals representative of the acceleration or deceleration of a vehicle, means being provided to process the signal by integrating or differentiating the signal and to compare the processed signal with a reference signal, there being means to provide an output when the reference signal is exceeded, the reference signal and/or the condition of processing the signal not being constant by varying, in a substantially predetermined manner with time. In preferred embodiments the variation in the reference signal and/or the condition of processing are varied so as to distinguish between a real accident where a dangerous situation arises, and a slight knock.
Preferably the means to provide an output signal are only activated when the signal representative of acceleration or deceleration exceeds a predetermined threshold.
Conveniently the processed signal is compared with a reference signal, with the reference signal varying in a predetermined manner with time.
Preferably the signal is integrated about an adjustable integration level, the integration level being adjusted in a substantially predetermined manner with time.
Advantageously the reference signal comprises a signal derived from a memory, the memory passing appropriate values to the comparator at appropriate instants in time.
Preferably different integration level values are stored in a memory, the memory passing appropriate values to the integrator at appropriate instands in time.
Conveniently the memory contains a plurality of profiles, each appropriate to a predetermined parameter or parameters, means being provided to determine the parameter(s) and to pass a signal representative of the parameter(s) to the memory so that an appropriate profile is selected, each profile containing comparator referen
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General Engineering (Netherlands ) B.V.
Harvey Jack B.
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