Triggering device for a vehicle safety system with an acceleration sensor

• US 5,809,439 A
• Filed: 07/12/1995
• Issued: 09/15/1998
• Est. Priority Date: 07/12/1994
• Status: Expired due to Fees

• Current Assignee: Autoliv AB (Autoliv Incorporated)
• Original Assignee: Autoliv AB (Autoliv Incorporated)
• Inventors: Damisch, Jurgen
• Primary Examiner(s): Teska, Kevin J.
• Assistant Examiner(s): Walker, Tyrone V.
• Application Number:
  US08/501,552
• Time in Patent Office: 1,161 Days
• Field of Search: 364/424.055, 364/424.056, 180/268, 180/271, 180/282, 280/727, 280/728.1, 280/734, 280/735, 307/10.1
• US Class Current: 701/45
• CPC Class Codes: B60R 2021/01322 comprising variable thresholds, e.g. depending from other collision parameters
• CPC Class Codes: B60R 21/0132 responsive to vehicle motion parameters , e.g. to vehicle longitudinal or transversal deceleration or speed value
• CPC Class Codes: G01P 15/08 with conversion into electric or magnetic values

Abstract

A triggering device for a vehicle safety device is provided with an acceleration sensor generating signals corresponding to a measured acceleration and a circuit processing the signals for generating a triggering signal when a predetermined threshold value for a vehicle collision is exceeded. To manufacture a triggering device of high security and reliability in an economical manner, the acceleration signals measured by the acceleration sensor are supplied to a threshold circuit having at least two threshold values for a specific vehicle. The threshold circuit activates a counter with a weighting factor that is increased from the first threshold value to the next threshold value. The counter adds received clock pulses to the given weighting factor and at each clock pulse is decremented by a count the weighting factor of which is below that of the first threshold value. The count of the counter is compared with a triggering threshold value, and when said triggering threshold value is reached, the triggering signal is produced. The counter is reset when the count of the counter becomes negative.

Claims

1. A triggering device for a vehicle safety system comprising:

a first acceleration sensor producing acceleration signals representing a measured acceleration;

a second acceleration sensor having a damping device for producing damped acceleration signals; and

a signal processor which processes said acceleration signals output from at least one of said first and second acceleration sensors and which produces at least one triggering signal, said signal processor including;

a first threshold value circuit having at least a first vehicle-specific acceleration threshold value and a second vehicle-specific acceleration threshold value and being arranged to receive said acceleration signals;

a timer circuit for providing clock pulses;

a first counter having a first adjustable weighting factor, said first weighting factor being adjusted in correspondence with the acceleration threshold value selected by said first threshold value circuit and being greater when said first threshold value circuit selects said second acceleration threshold value than when said first threshold value circuit selects said first acceleration threshold value, said first counter being activated by said first threshold value circuit to produce a first count, said first counter adding the value of said first weighting factor at each clock pulse to said first count, said first counter decrementing said first count at each clock pulse by a value that is less than said first weighting factor corresponding to said first acceleration threshold value;

a first comparator which compares said first count to a first triggering threshold value and when said first triggering threshold value is reached or exceeded by said first count, outputs a triggering signal for triggering said vehicle safety system;

a second comparator which compares said acceleration signals from said first acceleration sensor and said damped acceleration signals from said second acceleration sensor and outputs a difference signal corresponding to a difference between said signals output by said first and said second acceleration sensors; and

a second threshold value circuit for receiving said difference signal output from said second comparator, a second counter having a second weighting factor, said second counter being activated by said second threshold value circuit to produce a second count, said second counter adding the value of said second weighting factor to said second count at each clock pulse and also decrementing said second count by a value that is less than said second weighting factor at each clock pulse, and a third comparator which compares said second count with a second triggering threshold value and outputting a triggering signal when said second triggering threshold value is reached or exceeded, said second count being reset when said second count is negative.

2. The triggering device of claim 1, wherein said decrementing of said second count occurs in count steps, each of said count steps having a period of 1/2 n of the period of a clock pulse, n being a positive whole number.

3. The triggering device of claim 1, wherein said triggering signal for triggering said vehicle safety system is output only if both of said first and said second triggering threshold values are reached or exceeded.

4. A triggering device for a vehicle safety system comprising:

an acceleration sensor producing acceleration signals representing a measured acceleration;

an acceleration threshold determiner arranged to receive said acceleration signals and to determine whether said acceleration signals reach or exceed at least a first vehicle-specific acceleration threshold value and a second vehicle-specific acceleration threshold value;

a timer providing clock pulses;

a counter arranged to receive said clock pulses and being activated by said acceleration threshold determiner to produce a count, said counter incrementing said count by a first increment value for each clock pulse when said acceleration signal is below said first acceleration threshold value, said counter incrementing said count by a second increment value greater than said first increment value for each clock pulse when said acceleration signal is at or above said first acceleration threshold value but below said second acceleration threshold value, said counter incrementing said count by a third increment value greater than said second increment value for each clock pulse when said acceleration signal is at or above said second acceleration threshold value, and said counter decrementing said count by a decrement value less than said second increment value for each clock pulse; and

a triggering threshold determiner comparing said count to a triggering threshold value and, when said triggering threshold value is reached or exceeded by said count, outputting a triggering signal triggering said vehicle safety system.

5. The triggering device for a vehicle safety system of claim 4, wherein said acceleration threshold determiner further comprises at least one comparator comparing said acceleration signals to said acceleration threshold values.

6. The triggering device for a vehicle safety system of claim 4, wherein said counter resets said count when said count has a negative value.

7. The triggering device for a vehicle safety system of claim 4, further comprising a device for changing said triggering threshold value after a period of time that is specific to a vehicle, said period of time beginning from said activation of said counter.

8. The triggering device for a vehicle safety system of claim 4, further comprising a device for changing said triggering threshold value in stages.

9. The triggering device for a vehicle safety system of claim 4, wherein said second increment value is twice the value of said first increment value, and said third increment value is twice the value of said second increment value.

10. The triggering device for a vehicle safety system of claim 4, wherein said decrement value is half the value of said second increment value.

11. The triggering device for a vehicle safety system of claim 4, wherein the acceleration threshold determiner further determines whether said acceleration signals reach or exceed a third vehicle-specific acceleration threshold value, said counter incrementing said count by said third increment value for each clock pulse when said acceleration signal is at or above said second acceleration threshold value but below said third acceleration threshold value, and said counter incrementing said counter by a fourth increment value for each clock pulse when said acceleration signal is at or above said third acceleration threshold value.

12. The triggering device for a vehicle safety system of claim 11, wherein said second increment value is twice the value of said first increment value, said third increment value is twice the value of said second increment value, and said fourth increment value is twice the value of said third increment value.

13. The triggering device for a vehicle safety system of claim 11, wherein said decrement value is half the value of said second increment value.

14. A triggering device for a vehicle safety system comprising:

an acceleration sensor producing acceleration signals representing a measured acceleration;

a first acceleration threshold determiner arranged to receive said acceleration signals and to determine whether said acceleration signals reach or exceed at least a first vehicle-specific acceleration threshold value and a second vehicle-specific acceleration threshold value;

a timer providing clock pulses;

a first counter arranged to receive said clock pulses and being activated by said first acceleration threshold determiner to produce a first count, said first counter incrementing said count by a first increment value for each clock pulse when said acceleration signal is at or above said first acceleration threshold value but below said second acceleration threshold value, said counter incrementing said count by a second increment value greater than said first increment value for each clock pulse when said acceleration signal is at or above said second acceleration threshold value; and

a first triggering threshold determiner comparing said first count to a first triggering threshold value and, when said first triggering threshold value is reached or exceeded by said first count, outputting a first triggering signal for triggering said vehicle safety system.

15. The triggering device for a vehicle safety system of claim 14, further comprising a comparator comparing said acceleration signals from said acceleration sensor and damped acceleration signals from a second acceleration sensor and outputting a difference signal corresponding to a difference between said signals output by said first and second acceleration sensors.

16. The triggering device for a vehicle safety system of claim 15, further comprising:

a second acceleration threshold determiner being arranged to receive said difference signal output by said comparator;

a second counter arranged to receive said clock pulses and being activated by said second acceleration threshold value determiner to produce a second count, said second counter decrementing said second count by a decrement value for each clock pulse; and

a second triggering threshold determiner comparing said second count to a second triggering threshold value and, when said second count reaches or becomes less than said second triggering threshold value, outputting a second triggering signal for triggering said vehicle safety system.

17. The triggering device for a vehicle safety system of claim 16, wherein said decrementing of said second count occurs in count steps, each of said count steps having a period of 1/2 n of the period of a clock pulse, n being a positive whole number.

18. The triggering device for a vehicle safety system of claim 16, wherein said vehicle safety system is triggered only if both of said first and said second triggering signals are output.