Capacitive occupant detection apparatus

• US 20100315099A1
• Filed: 06/08/2010
• Published: 12/16/2010
• Est. Priority Date: 06/16/2009
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Ootaka, Kouji
• Granted Patent: US 8,405,408 B2
• Time in Patent Office: Days
• US Class Current: 324/679
• CPC Class Codes: B60N 2/002 Seats provided with an occupancy detection means mounted therein or thereon detection means responsive to presence or absence of children B60N2/266
• CPC Class Codes: B60R 2021/01184 Fault detection or diagnostic circuits in power circuits B60R2021/01129
• CPC Class Codes: B60R 21/01532 using electric or capacitive field sensors

Abstract

A capacitive occupant detecting apparatus includes a voltage applying portion, a capacitance sensor, a capacitor, a storing portion, a measuring portion, and a calculating portion. The voltage applying portion applies an alternating-current voltage signal to the capacitance sensor and the capacitor. The storing portion stores a reference voltage. The measuring portion detects a first voltage in accordance with an electric current that flows between the voltage applying portion and the capacitor when the alternating-current voltage signal is applied to the capacitor. The measuring portion detects a second voltage in accordance with an electric current output from the capacitance sensor when the alternating-current voltage is applied to the capacitance sensor. The calculating portion detects an abnormality of the voltage applying portion based on the first voltage and the reference voltage, and determines an object disposed on the seat based on the second voltage.

Claims

1. A capacitive occupant detecting apparatus comprising:

a voltage applying portion configured to generate an alternating-current voltage signal;

a capacitance sensor including an electrode disposed in a seat of a vehicle, the capacitance sensor configured to output an electric current in accordance with a change in an electric field generated between the electrode and a vehicle body when the alternating-current voltage signal is applied to the electrode, the vehicle body coupled with a vehicle grounded portion;

a line coupling the voltage applying portion and the capacitance sensor;

a capacitor coupled with the line so as to be applied with the alternating-current voltage signal;

a storing portion configured to store a reference voltage;

a measuring portion configured to detect a first voltage in accordance with an electric current that flows between the voltage applying portion and the capacitor when the alternating-current voltage signal is applied to the capacitor, the measuring portion configured to detect a second voltage in accordance with the electric current output from the capacitance sensor when the alternating-current voltage is applied to the capacitance sensor; and

a calculating portion configured to detect an abnormality of the voltage applying portion based on the first voltage and the reference voltage, the calculating portion configured to determine an object disposed on the seat based on the second voltage.

2. The capacitive occupant detection apparatus according to claim 1, wherein

when the first voltage is different from the reference voltage, the calculating portion determines that a frequency of the alternating-current voltage signal is abnormal.

3. The capacitive occupant detection apparatus according to claim 1, wherein

the reference voltage is the first voltage detected by the measuring portion before the vehicle is operated, and

when the first voltage detected by the measuring portion while the vehicle is operated is different from the reference voltage, the calculating portion determines that a frequency of the alternating-current voltage signal is abnormal.

4. The capacitive occupant detection apparatus according to claim 1, wherein

the reference voltage is the first voltage detected by the measuring portion in an inspection process.

5. The capacitance occupant detection apparatus according to claim 1, wherein

the reference voltage has a predetermined voltage range, and

when the first voltage is out of the predetermined voltage range, the calculating portion determines that a frequency of the alternating-current voltage signal is abnormal.

6. The capacitance occupant detection apparatus according to claim 1, further comprising

a first switch disposed on the line coupling the voltage applying portion and the capacitance sensor, and

a second switch disposed on another line coupling the line and the capacitor, wherein

the alternating-current voltage is selectively applied to the capacitance sensor and the capacitor by controlling the first switch and the second switch.