Abstract: The present invention relates to an acceleration sensor which can be provided in a place with extreme ambient temperature variations, for example, near a vehicle engine, and an acceleration detecting system having the acceleration sensor, which are used to control an occupant protection device such as an airbag. In an acceleration sensor (1, 40, 50, 160), gain of an amplifier circuit (4, 5, 6, 41, 42, 43, 51) which differentially amplifies outputs of a piezo-electric element (3) is adjusted by temperature compensation means (9), and thereby an output-temperature characteristic of the piezo-electric element (3) is compensated. Also, a capacitor (8) is inserted in parallel with the piezo-electric element (3), and thereby a composite capacity is increased. By this, a lower cut-off frequency is set to a lower frequency without increasing resistor values of a bias resistor circuit (7).

Abstract: If deceleration in excess of a predetermined value is detected (step 104 in FIG. 2), a speed integral value &Dgr;V as time integration of the deceleration is calculated (step 110 in FIG. 2). A segment length of a characteristic curve of the speed integral value &Dgr;V in a predetermined range is calculated (steps 112, 114 in FIG. 2) . If it is decided that the segment length is smaller than a predetermined value l2 (step 116 in FIG. 2), the crash is decided as the low speed crash, etc. other than a soft crash. An air bag is inflated if the speed integral value &Dgr;V exceeds a predetermined threshold value VTH, whereas the speed integral value &Dgr;V is incremented by a predetermined value &agr; (step 118 in FIG. 2) if it is decided that the segment length exceeds l2 (step 116 in FIG. 2). Then, if it is decided that the speed integral value &Dgr;V exceeds the threshold value VTH (step 112 in FIG. 2), inflation of the air bag is executed to detect generation of the soft crash.

Abstract: A control apparatus of an occupant protection device has at least one front acceleration sensor provided in a front part of a vehicle in addition to a room acceleration sensor provided in a room of the vehicle. The front acceleration sensor detects an acceleration of the vehicle and gives the control unit a sensor output representative thereof. The control unit, when the sensor output of the front acceleration sensor is a sensor output caused by a collision of the vehicle, detects a variational quantity of the sensor output of the front acceleration sensor based on sensor outputs of the front acceleration sensor at two different time points, and increases an integrated value of an acceleration signal of the room acceleration sensor based on the variational quantity. Then, when the integrated value of the room acceleration sensor exceeds a threshold value, the occupant protection device is driven.

Abstract: If deceleration in excess of a predetermined value is detected (step 104 in FIG.2), a speed integral value &Dgr;V as time integration of the deceleration is calculated (step 110 in FIG.2). A segment length of a characteristic curve of the speed integral value &Dgr;V in a predetermined range is calculated (steps 112, 114 in FIG. 2). If it is decided that the segment length is smaller than a predetermined value l2 (step 116 in FIG. 2), the crash is decided to be a low speed crash, etc. other than a soft crash. An air bag is inflated if the speed integral value &Dgr;V exceeds a predetermined threshold value VTH, whereas the speed integral value &Dgr;V is incremented by a predetermined value &agr; (step 118 in FIG. 2) if it is decided that the segment length exceeds l2 (step 116 in FIG. 2). Then, if it is decided that the speed integral value &Dgr;V exceeds the threshold value VTH (step 112 in FIG. 2), inflation of the air bag is executed with detection of a soft crash.

Abstract: A control apparatus of an occupant protection device detects whether a vehicle is in a collision requiring to drive the occupant protection device based on at least one front acceleration sensor provided in a front part of the vehicle, in addition to a collision detection based on a room acceleration sensor provided in a room of the vehicle. When the collision is detected based on the front acceleration sensor, an integrated value of an acceleration signal of the room acceleration sensor is increased. Since the front acceleration sensor is provided in the front part of the vehicle, the front acceleration sensor detects a collision acceleration early and gives a sensor output to the control unit, even in case of a collision in which a collision acceleration transmitted to the room acceleration sensor may be weakened.

Abstract: A control apparatus of an occupant protection device, in addition to a room acceleration sensor provided in a room of a vehicle, has at least one front acceleration sensor provided in a front part of the vehicle. The front acceleration sensor, when detecting a predetermined collision acceleration, gives a detection signal to a control unit. The control unit sets a second threshold value lower than a first threshold value if the detection signal is input, and drives the occupant protection device when an integrated value of an acceleration signal of the room acceleration sensor exceeds the second threshold value. Since the front acceleration sensor is provided in the front part of the vehicle, even when a collision acceleration transmitted to the room acceleration sensor is weakened, the front acceleration sensor detects the collision acceleration early and gives the detection signal to the control unit.

Abstract: If an impact acceleration Gt in excess of a predetermined value is detected (step 102), a speed integral value &Dgr;V is calculated (step 110) and a length of a line segment of the impact acceleration with a passage of time is calculated (steps 112, 114). If a rate of an increment of the speed integral value &Dgr;V to the length of the line segment within a predetermined interval is smaller than a predetermined value R, it is decided that resonance is caused. Then, it is decided (step 122) whether or not the speed integral value &Dgr;Vt exceeds a new threshold value which is set on the more negative side from a threshold value &Dgr;VTH which is defined by V(G), by a predetermined value &agr; (step 120). If it is decided that the speed integral value &Dgr;Vt exceeds the new threshold value, an inflation of an air bag is carried out (step 124).