PASSENGER DETECTION SYSTEM

• US 20010013697A1
• Filed: 11/13/1998
• Published: 08/16/2001
• Est. Priority Date: 11/17/1997
• Status: Active Grant

• Current Assignee: Honda Elesys Co., Ltd. (Nidec Corporation)
• Original Assignee: NEC Corporation
• Inventors: SAITO, TAKASHI, OFUJI, MASAHIRO
• Granted Patent: US 6,325,413 B2
• Time in Patent Office: Days
• US Class Current: 280/735
• CPC Class Codes: B60R 21/01532 using electric or capacitive field sensors
• CPC Class Codes: B60R 21/33 Arrangements for non-electric triggering of inflation electrical circuits for triggering safety arrangements B60R21/01
• CPC Class Codes: G01V 3/088 operating with electric fields G01V3/082 takes precedence

Abstract

A passenger detection system comprises an antenna electrode which is provided to the dashboard of a car, an oscillation circuit for generating a high frequency low voltage oscillation signal in order to generate a weak alternating electric field around the antenna electrode, a current detection section for detecting a transmission current which passes between the oscillation circuit and the antenna electrode depending on the weak alternating electric field which is generated around the antenna electrode, a phase difference detection section for detecting the phase difference between the oscillation signal supplied from the oscillation circuit and an output signal which is supplied to the antenna electrode, and a control circuit for judging the presence or absence of a passenger seated on the seat based on the detected phase difference and judging the distance between the passenger and the dashboard based on the detected transmission current. The passenger detection system is connected with an air bag unit, and the air bag unit is set at a ‘no deployment mode’ if it is judged that no passenger is seated on the seat or the distance between the passenger and the dashboard is less than a minimum allowable distance, thereby the passenger who is close to the dashboard is protected from secondary injury due to strong deployment of the air bag.

Claims

1. A passenger detection system comprising:

an antenna electrode which is provided to a portion of a vehicle in front of a seat of the vehicle so as to face a passenger seated on the seat;

an oscillation means for generating a high frequency low voltage oscillation signal in order to generate a weak alternating electric field around the antenna electrode;

a current detection means for detecting a transmission current which passes between the oscillation means and the antenna electrode depending on the weak alternating electric field which is generated around the antenna electrode; and

a judgment means for judging the distance between the passenger and the portion of the vehicle based on the transmission current which has been detected by the current detection means.

2. A passenger detection system as claimed in

claim 1

, wherein the passenger detection system is connected with an air bag unit which is capable of deploying an air bag in front of the passenger in case of collision so that data concerning the distance judged by the judgment means can be sent to the air bag unit, and the air bag unit is set at a deployment mode in which the air bag unit deploys the air bag on collision or a no deployment mode in which the air bag unit does not deploy the air bag on collision according to the data concerning the distance sent from the judgment means.

3. A passenger detection system as claimed in

claim 2

, wherein the judgment means executes judgment on whether the distance between the passenger and the portion of the vehicle is more than a minimum allowable distance or less than the minimum allowable distance by comparing the transmission current detected by the current detection means with a prestored threshold value concerning the transmission current corresponding to the minimum allowable distance, and the air bag unit is set at the no deployment mode if the distance is judged to be less than the minimum allowable distance.

4. A passenger detection system as claimed in

claim 3

, wherein the antenna electrode is provided to the dashboard of a car.

5. A passenger detection system as claimed in

claim 4

, wherein a control unit is made up by enclosing the oscillation means, the current detection means and the judgment means in a common housing, and the control unit is placed inside or near the dashboard.

6. A passenger detection system as claimed in

claim 1

, wherein the antenna electrode is provided so that the area of the antenna electrode facing part of the passenger will be as large as possible.

7. A passenger detection system as claimed in

claim 1

, further comprising an amplitude control means for controlling the voltage amplitude of the oscillation signal which is supplied by the oscillation means to the antenna electrode at an almost constant value.

8. A passenger detection system as claimed in

claim 1

, further comprising a power circuit for generating a single uniform DC voltage utilizing power derived from a battery, in which the single uniform DC voltage supplied by the power circuit is utilized as the system power source for circuits in the passenger detection system including the oscillation means, the current detection means and the judgment means.

9. A passenger detection system comprising:

an antenna electrode which is provided to a portion of a vehicle in front of a seat of the vehicle so as to face a passenger seated on the seat;

an oscillation means for generating a high frequency low voltage oscillation signal in order to generate a weak alternating electric field around the antenna electrode;

a current detection means for detecting a transmission current which passes between the oscillation means and the antenna electrode depending on the weak alternating electric field which is generated around the antenna electrode;

a phase difference detection means for detecting the phase difference between the oscillation signal supplied from the oscillation means and an output signal which is supplied to the antenna electrode; and

a judgment means for judging the presence or absence of a passenger seated on the seat based on the phase difference which has been detected by the phase difference detection means and judging the distance between the passenger and the portion of the vehicle based on the transmission current which has been detected by the current detection means.

10. A passenger detection system as claimed in

claim 9

, wherein the passenger detection system is connected with an air bag unit which is capable of deploying an air bag in front of the passenger in case of collision so that data concerning the judgment can be sent from the passenger detection system to the air bag unit, and the air bag unit is set at a deployment mode in which the air bag unit deploys the air bag on collision or a no deployment mode in which the air bag unit does not deploy the air bag on collision according to the data concerning the judgment sent from the judgment means.

11. A passenger detection system as claimed in

claim 10

, wherein the judgment means executes judgment on the presence or absence of a passenger seated on the seat by comparing the phase difference detected by the phase difference detection means with a prestored threshold value concerning the phase difference and executes judgment on whether the distance between the passenger and the portion of the vehicle is more than a minimum allowable distance or less than the minimum allowable distance by comparing the transmission current detected by the current detection means with another prestored threshold value concerning the transmission current corresponding to the minimum allowable distance, and the air bag unit is set at the no deployment mode if it is judged that no passenger is seated on the seat or the distance is less than the minimum allowable distance.

12. A passenger detection system as claimed in

claim 11

, wherein the antenna electrode is provided to the dashboard of a car.

13. A passenger detection system as claimed in

claim 12

, wherein a control unit is made up by enclosing the oscillation means, the current detection means, the phase difference detection means and the judgment means in a common housing, and the control unit is placed inside or near the dashboard.

14. A passenger detection system as claimed in

claim 9

, wherein the antenna electrode is provided so that the area of the antenna electrode facing part of the passenger will be as large as possible.

15. A passenger detection system as claimed in

claim 9

, further comprising an amplitude control means for controlling the voltage amplitude of the oscillation signal which is supplied by the oscillation means to the antenna electrode at an almost constant value.

16. A passenger detection system as claimed in

claim 9

, further comprising a power circuit for generating a single uniform DC voltage utilizing power derived from a battery, in which the single uniform DC voltage supplied by the power circuit is utilized as the system power source for circuits in the passenger detection system including the oscillation means, the current detection means, the phase difference detection means and the judgment means.

17. A passenger detection system as claimed in

claim 9

, wherein the phase difference detection means detects the phase difference between signals at both ends of the current detection means.

18. A passenger detection system as claimed in

claim 9

, wherein the phase difference detection means detects the phase difference between the oscillation signal and the output signal, by detecting the phase difference between a rising/falling edge of a square wave signal corresponding to the oscillation signal and a rising/falling edge of a square wave signal corresponding to the output signal.

19. A passenger detection system as claimed in

claim 9

, wherein the oscillation means generates the high frequency low voltage oscillation signal substantially in the form of a square wave.

20. A passenger detection system as claimed in

claim 19

, wherein an MPU (MicroProcessor Unit) is utilized as the oscillation means for generating the high frequency low voltage oscillation signal in the form of a square wave.

21. A passenger detection method comprising the steps of:

a field generation step in which a weak alternating electric field is generated by an oscillation means around an antenna electrode which is provided to a portion of a vehicle in front of a seat of the vehicle so as to face a passenger seated on the seat;

a transmission current detection step in which a transmission current which passes in the antenna electrode depending on the weak alternating electric field is detected; and

a judgment step in which the distance between the passenger and the portion of the vehicle is judged based on the transmission current which has been detected in the transmission current detection step.

22. A passenger detection method as claimed in

claim 21

, further comprising the steps of:

a data communication step in which data concerning the judgment on the distance is sent to an air bag unit; and

an air bag unit setting step in which the air bag unit is set at a deployment mode in which the air bag unit deploys the air bag on collision or a no deployment mode in which the air bag unit does not deploy the air bag on collision according to the data concerning the judgment on the distance.

23. A passenger detection method as claimed in

claim 22

, wherein in the judgment step, whether the distance between the passenger and the portion of the vehicle is more than a minimum allowable distance or less than the minimum allowable distance is judged by comparing the transmission current detected in the transmission current detection step with a threshold value concerning the transmission current corresponding to the minimum allowable distance, and in the air bag unit setting step, the air bag unit is set at the no deployment mode if the distance is judged to be less than the minimum allowable distance.

24. A passenger detection system as claimed in

claim 23

, wherein the antenna electrode is provided to the dashboard of a car.

25. A passenger detection method comprising the steps of:

a field generation step in which a weak alternating electric field is generated by an oscillation means around an antenna electrode which is provided to a portion of a vehicle in front of a seat of the vehicle so as to face a passenger seated on the seat;

a transmission current detection step in which a transmission current which passes in the antenna electrode depending on the weak alternating electric field is detected;

a phase difference detection step in which the phase difference between an oscillation signal which is supplied from the oscillation means and an output signal which is supplied to the antenna electrode is detected; and

a judgment step in which the presence or absence of a passenger seated on the seat is judged based on the phase difference which has been detected in the phase difference detection step and the distance between the passenger and the portion of the vehicle is judged based on the transmission current which has been detected in the transmission current detection step.

26. A passenger detection method as claimed in

claim 25

, further comprising the steps of:

a data communication step in which data concerning the judgment in the judgment step is sent to an air bag unit; and

an air bag unit setting step in which the air bag unit is set at a deployment mode in which the air bag unit deploys the air bag on collision or a no deployment mode in which the air bag unit does not deploy the air bag on collision according to the data concerning the judgment.

27. A passenger detection method as claimed in

claim 26

, wherein in the judgment step, the presence or absence of a passenger seated on the seat is judged by comparing the phase difference detected in the phase difference detection step with a prestored threshold value concerning the phase difference and whether the distance between the passenger and the portion of the vehicle is more than a minimum allowable distance or less than the minimum allowable distance is judged by comparing the transmission current detected in the transmission current detection step with another threshold value concerning the transmission current corresponding to the minimum allowable distance, and in the air bag unit setting step, the air bag unit is set at the no deployment mode if it is judged that no passenger is seated on the seat or the distance is less than the minimum allowable distance.

28. A passenger detection system as claimed in

claim 27

, wherein the antenna electrode is provided to the dashboard of a car.

29. A passenger detection system as claimed in

claim 25

, wherein in the phase difference detection step, the phase difference between the oscillation signal and the output signal is detected by detecting the phase difference between a rising/falling edge of a square wave signal corresponding to the oscillation signal and a rising/falling edge of a square wave signal corresponding to the output signal.

30. A passenger detection system as claimed in

claim 25

, wherein the oscillation means generates a high frequency low voltage square wave oscillation signal in order to generate the weak alternating electric field.

31. A passenger detection system as claimed in

claim 30

, wherein an MPU (MicroProcessor Unit) is utilized as the oscillation means for generating the high frequency low voltage square wave oscillation signal.