Passenger detection system

• US 7,401,532 B2
• Filed: 03/28/2006
• Issued: 07/22/2008
• Est. Priority Date: 03/31/2005
• Status: Expired due to Fees

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Wanami, Shingo
• Primary Examiner(s): Lefkowitz; Edward
• Assistant Examiner(s): DAVIS, OCTAVIA L
• Application Number:
  US11/390,664
• Publication Number:
  US 20060219460A1
• Time in Patent Office: 847 Days
• Field of Search: 738/626.26
• US Class Current: 73/862.626
• CPC Class Codes: B60R 21/01532 using electric or capacitive field sensors

Abstract

A passenger detection system for a person on a seat of a vehicle, includes a long range capacitance sensor for measuring a long range capacitance between a seating portion of the seat and a body of the vehicle and a short range capacitance sensor for measuring a short range capacitance in the seat, and a detection unit for detecting a passenger on the seat based on the measured long range capacitance and the measured short range capacitance. Therefore, the passenger detection system accurately detects a passenger on the seat of the vehicle while suppressing a detection error caused by an external effect.

Claims

1. A passenger detection system for a person on a seat of a vehicle, comprising:

a first capacitance sensor for measuring a first capacitance between a seating portion of the seat and a body of the vehicle;

a second capacitance sensor different than the first capacitance sensor for measuring a second capacitance within the seating portion of the seat; and

a detection unit which detects a passenger on the seat based on the measured first capacitance and the measured second capacitance;

wherein

the detection unit detects the passenger on the seat base on a comparison between the measured first capacitance and a variable first threshold value, the variable first threshold value being continuously determined by a comparison between the measured first capacitance and the measured second capacitance.

2. The passenger detection system according to claim 1, wherein:

the first and second capacitance sensors are constructed with a plurality of electrodes located in the seat, the electrodes having the same electric potential and being electrically separated from the body;

the first capacitance sensor measures as the first capacitance a capacitance between the body and the electrodes; and

the second capacitance sensor measures as the second capacitance a capacitance between the electrodes.

3. The passenger detection system according to claim 1, wherein:

the first and second capacitance sensors are constructed with a first electrode and a second electrode having different surface areas;

the second capacitance sensor measures as the second capacitance a capacitance between the first and second electrodes; and

the first electrode has a surface area larger than the second electrode.

4. The passenger detection system according to claim 3, wherein one of the first and second electrodes has the same electric potential with the body.

5. The passenger detection system according to claim 1, wherein:

when the first capacitance is smaller than the variable first threshold value which is changed in accordance with the second capacitance, the detection unit detects that the passenger is a child or no passenger is on the seat; and

when the first capacitance is larger than a variable second threshold value which is continuously changed in accordance with the second capacitance and is larger than the variable first threshold, the detection unit detects that the passenger is a grown person.

6. The passenger detection system according to claim 5, wherein:

in a case where the first capacitance is between the variable first threshold value and the variable second threshold value, the detection unit detects that the passenger is a grown person when the second capacitance is smaller than a third threshold value.

7. The passenger detection system according to claim 1, wherein the detection unit detects the passenger on the seat based on a predetermined relationship between the measured first capacitance and the measured second capacitance.

8. The passenger detection system according to claim 1, wherein the detection unit detects the passenger on the seat based on a comparison between the measured first capacitance and a variable second threshoid value different than the variable first threshold value, the variable second threshold value being continuously determined by a comparison between the measured first capacitance and the measured second capacitance.

9. The passenger detection system according to claim 8, wherein the detection unit detects the passenger on the seat based on a comparison between the measured second capacitance and a third threshold value, the third threshold value being a specified value.

10. A passenger detection system for a person on a seat of a vehicle, comprising:

a first capacitance sensor having electrodes spaced a first distance for measuring a first capacitance between a seating portion of the seat and a body of the vehicle;

a second capacitance sensor having electrodes spaced a second distance less than the first distance for measuring a second capacitance within the seating portion of the seat; and

a detection unit which detects a passenger on the seat based on the measured first capacitance and the measured second capacitance;

wherein

the detection unit detects the passenger on the seat base on a comparison between the measured first capacitance and a variable first threshold value, the variable first threshold value being continuously determined by a comparison between the measured first capacitance and the measured second capacitance.

11. The passenger detection system according to claim 10, wherein:

the first and second capacitance sensors are constructed with a plurality of electrodes located in the seat, the electrodes having the same electric potential and being electrically separated from the body;

the first capacitance sensor measures as the first capacitance a capacitance between the body and the electrodes; and

the second capacitance sensor measures as the second capacitance a capacitance between the electrodes.

12. The passenger detection system according to claim 10, wherein:

the first and second capacitance sensors are constructed with a first electrode and a second electrode having different surface areas;

the second capacitance sensor measures as the second capacitance a capacitance between the first and second electrodes; and

the first electrode has a surface area larger than the second electrode.

13. The passenger detection system according to claim 12, wherein one of the first and second electrodes has the same electric potential with the body.

14. The passenger detection system according to claim 10, wherein the detection unit detects the passenger on the seat based on a comparison between the measured first capacitance and a variable second threshold value different than the variable first threshold value, the variable second threshold value being determined by a comparison between the measured first capacitance and the measured second capacitance.

15. The passenger detection system according to claim 14, wherein the detection unit detects the passenger on the seat based on a comparison between the measured second capacitance and a third threshold value, the third threshold value being a specified value.

16. A passenger detection system for a person on a seat of a vehicle, comprising:

a first capacitance sensor for measuring a first capacitance between a seating portion of the seat and a backrest portion of the seat of the vehicle;

a second capacitance sensor for measuring a second capacitance within the seating portion of the seat; and

a detection unit which detects a passenger on the seat based on the measured first capacitance and the measured second capacitance;

wherein

the detection unit detects the passenger on the seat base on a comparison between the measured first capacitance and a variable first threshold value, the variable first threshold value being continuously determined by a comparison between the measured first capacitance and the measured second capacitance.

17. The passenger detection system according to claim 16, wherein:

the first and second capacitance sensors are constructed with a plurality of electrodes located in the seat, the electrodes having the same electric potential and being electrically separated from the body;

the first capacitance sensor measures as the first capacitance a capacitance between the body and the electrodes; and

the second capacitance sensor measures as the second capacitance a capacitance between the electrodes.

18. The passenger detection system according to claim 16, wherein:

the first and second capacitance sensors are constructed with a first electrode and a second electrode having different surface areas;

the second capacitance sensor measures as the second capacitance a capacitance between the first and second electrodes; and

the first electrode has a surface area larger than the second electrode.

19. The passenger detection system according to claim 18, wherein one of the first and second electrodes has the same electric potential with the body.

20. The passenger detection system according to claim 16, wherein the detection unit detects the passenger on the seat based on a comparison between the measured first capacitance and a variable second threshold value different than the variable first threshold value, the second threshold value being continuously determined by a comparison between the measured first capacitance and the measured second capacitance.

21. The passenger detection system according to claim 20, wherein the detection unit detects the passenger on the seat based on a comparison between the measured second capacitance and a third threshold value, the third threshold value being a specified value.