Activation system and method for passenger protection device

Abstract

An activation system for a passenger protection device comprises a pair of communication wires, a central unit for detecting currents flowing in the communication wires, and a satellite unit for varying the currents flowing in the communication wires based on output data of an acceleration detection sensor. The central unit calculates a sum of the detected currents and compares the sum with a first predetermined level to detect the output data of the sensor. The central unit also calculates a difference between the detected currents and compares the difference with a second predetermined level, thereby detecting failure in the communication wires and stopping activation of the passenger protection device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:

FIG. 1 is a schematic view showing an airbag activation system according to one embodiment of the present invention;

FIG. 2 is a block diagram showing the airbag activation system shown in FIG. 1;

FIG. 3 is a signal diagram showing an operation of a current detection circuit shown in FIG. 2;

FIG. 4 is a flow diagram showing data receiving processing of a microcomputer shown in FIG. 2;

FIG. 5 is a block diagram showing mechanism of generation of an induction noise;

FIG. 6 is a signal diagram showing current detection in the case of superposition of the induction noise shown in FIG. 5;

FIG. 7 is a block diagram showing mechanism of generation of failure in a communication lie;

FIG. 8 is a signal diagram showing current detection in the case of failure shown in FIG. 7;

FIG. 9 is a block diagram showing a conventional airbag activation system;

FIG. 10 is a signal diagram showing an operation of a current detection circuit shown in FIG. 9;

FIG. 11 is a signal diagram showing current detection in the case of superposition of induction noise in the conventional system; and

FIG. 12 is a signal diagram showing current detection in the case of failure in the communication line in the conventional system.

Claims

1. An activation system for a passenger protection device mounted in a vehicle, the system comprising: a pair of communication wires;a central unit connected to the communication wires for detecting currents flowing in the communication wires and controlling activation of the passenger protection device based on detected currents; anda satellite unit including a sensor and connected to the communication wires to be located away from the central unit, the satellite unit varying the currents flowing in the communication wires based on output data of the sensor,wherein the central unit includes a pair of current detection means for detecting the currents in the communication wires, respectively, to detect the output data of the sensor based on both of the detected currents.

2. The activation system according to claim 1, wherein the central unit calculates a sum of the detected currents and detects the output data of the sensor based on the sum of the currents.

3. The activation system according to claim 1, wherein the central unit calculates a difference between the detected currents and detects failure in the communication wires based on the difference between the detected currents.

4. The activation system according to claim 3, wherein the central unit detects the failure when the difference between the detected currents continues to be larger than a predetermined level for more than a predetermined time.

5. The activation system according to claim 1, wherein the sensor of the satellite unit is a collision detection sensor for detecting at least one of collisions of the vehicle at a front area and a side area.

6. The activation system according to claim 1, wherein the sensor of the satellite unit is a roll rate detection sensor for detecting a roll-over of the vehicle.

7. The activation system according to claim 1, wherein the sensor of the satellite unit is a passenger detection sensor for detecting a passenger in the vehicle.

8. The activation system according to claim 1, wherein the sensor of the satellite unit is a pressure detection sensor provided within a door of the vehicle for detecting a pressure within the door, which changes upon collision of the vehicle.

9. The activation system according to claim 2, wherein the central unit compares the sum of the currents with a first predetermined level to detect the output data of the sensor.

10. The activation system according to claim 9, wherein the central unit calculates a difference between the detected currents and compares the difference with a second predetermined level smaller than the first predetermined level to detect failure in the communication wires.

11. An activation method for a passenger protection device mounted in a vehicle, the method comprising: detecting a predetermined parameter by a sensor of a satellite unit;varying currents flowing through communication wires between a central unit and the satellite unit in accordance with an output of the sensor;detecting both of the currents flowing in the communication wires; andcontrolling activation of the passenger protection device based on both of the currents.

12. The activation method according to claim 11, wherein the controlling includes: calculating a sum of both of the currents; andcomparing the sum with a first predetermined level to detect the output of the sensor.

13. The activation method according to claim 12, wherein the controlling includes: calculating a difference between both of the currents;comparing the difference with a second predetermined level, which is smaller than the first predetermined level to detect failure in the communication wires; andstopping the activation of the passenger protection device when the difference is larger than the second predetermined level.

14. The activation method according to claim 11, wherein the controlling includes: calculating a difference between both of the currents;comparing the difference with a predetermined level to detect failure in the communication wires; andstopping the activation of the passenger protection device when the difference is larger than the predetermined level.