Sensor detection controller and occupant detection apparatus having the same

• US 8,335,617 B2
• Filed: 09/08/2011
• Issued: 12/18/2012
• Est. Priority Date: 09/10/2010
• Status: Active Grant

• Current Assignee: DENSO Corporation, Nippon Soken, Inc.
• Original Assignee: DENSO Corporation, Nippon Soken, Inc.
• Inventors: Maeda, Noboru, Ootaka, Kouji, Satake, Masayoshi, Mori, Hiroyuki
• Primary Examiner(s): Cheung, Mary
• Assistant Examiner(s): Marc, McDieunel
• Application Number:
  US13/199,752
• Publication Number:
  US 20120065845A1
• Time in Patent Office: 467 Days
• Field of Search: 701/45, 701/47, 701/49, 340/506, 340/522, 340/529, 340/541, 340/577, 340/628, 340/963, 340/968, 602/76, 602/77, 602/85, 342/26.D, 123/688, 123/703, 204/426, 204/429, 102/427, 356/401, 367/136
• US Class Current: 701/47
• 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: G01R 31/2829 Testing of circuits in sensor or actuator systems testing of apparatus for measuring electric or magnetic variables G01R35/00; testing of indicating or recording apparatus G01D; in airbag systems B60R21/0173; checking gas analysers G01N33/007; monitoring or fail-safe circuits for electromagnets H01F7/1844

Abstract

A sensor detection controller is used in combination with a capacitive sensor that is mounted on a seat of a vehicle in such a manner that a capacitance of the capacitive sensor changes according to whether the seat is occupied. The sensor detection controller has a fault detection mode and a normal detection mode. The sensor detection controller includes a signal source for applying an amplitude signal to the capacitive sensor, a switch for switching a signal path, through which the amplitude signal is applied, between the fault detection mode and the normal detection mode, a signal detector for detecting a change in a voltage or a current of the amplitude signal when the amplitude signal is applied, and an impedance member connected to the signal path.

Claims

1. A sensor detection controller for use in combination with a capacitive sensor, the capacitive sensor including first and second electrode plates and mounted on a seat of a vehicle in such a manner that a capacitance of the capacitive sensor changes according to whether the seat is occupied, the sensor detection controller having a fault detection mode for detecting a fault in the capacitive sensor and a normal detection mode for detecting whether the seat is occupied based on a change in the capacitance, the sensor detection controller comprising:

a signal source configured to apply an amplitude signal having a variable amplitude to the capacitive sensor;

a switching device configured to switch a signal path, through which the amplitude signal is applied, between the fault detection mode and the normal detection mode, the signal path including a first path through which the amplitude signal is applied to the first electrode plate and a second path through which the amplitude signal is applied to the second electrode plate;

a signal detector configured to detect a change in a voltage or a current of the amplitude signal when the amplitude signal is applied;

a control circuit configured to control the switching device and the signal detector; and

an impedance member having a predetermined impedance value and connected to the signal path, the impedance member including a first member connected to the first path and a second member connected to the second path.

2. The sensor detection controller according to claim 1, wherein

the impedance value of the impedance member is set so that the current on the signal path is equal to or less than a maximum current value to which the signal source is capable of applying the sinusoidal signal without distortion and equal to or greater than a minimum current value necessary for both the fault detection mode and the normal detection mode.

3. The sensor detection controller according to claim 2, wherein

the impedance of the impedance member is in a range satisfying the following inequality:

4. The sensor detection controller according to claim 1, wherein

at least one of the first and second members includes a resistor.

5. An occupant detection apparatus for a vehicle comprising:

the capacitive sensor of claim 1, and

the sensor detection controller of claim 1.

6. A sensor detection controller for use in combination with a sensor, the sensor creating an electric field or radiating one of an electromagnetic wave and a sound wave, the sensor detection controller having a fault detection mode for detecting a fault in the sensor and a normal detection mode for performing a predetermined detection operation by using the sensor, the sensor detection controller comprising:

a signal source configured to apply an amplitude signal having a variable amplitude to the sensor;

a first switching device configured to switch a signal path, through which the amplitude signal is applied, between the fault detection mode and the normal detection mode;

a signal detector configured to detect a change in a voltage or a current of the amplitude signal when the amplitude signal is applied;

a control circuit configured to control the first switching device and the signal detector;

an impedance member having a predetermined impedance value and connected to the signal path;

a short circuit configured to short-circuit the impedance member; and

a second switching device configured to selectively activate and deactivate the short circuit, wherein

the control circuit causes the second switching device to deactivate the short circuit in the fault detection mode and causes the second switching device to activate the short circuit in the normal detection mode.

7. The sensor detection controller according to claim 6, wherein

the impedance value of the impedance member is set so that the current on the signal path is equal to or less than a maximum current value to which the signal source is capable of applying the sinusoidal signal without distortion and equal to or greater than a first minimum current value necessary for the fault detection mode.

8. The sensor detection controller according to claim 7, wherein

the impedance value of the impedance member is in a range satisfying the following inequality:

9. The sensor detection controller according to claim 6, wherein

at least one of the first and second members includes a resistor.

10. The sensor detection controller according to claim 6, wherein

the sensor is a capacitive sensor having a predetermined capacitance and including a plurality of electrode plates, and

the detection operation is performed based on a change in the capacitance.

11. An occupant detection apparatus for a vehicle comprising:

the sensor of claim 6, and

the sensor detection controller of claim 6, wherein

the sensor is a capacitive sensor and mounted on a seat of a vehicle in such a manner that a capacitance of the capacitive sensor changes according to whether the seat is occupied, and

the detection operation is performed based on a change in the capacitance to determine whether the seat is occupied.