Capacitive occupant sensor and capacitive occupant detection apparatus

• US 20110074447A1
• Filed: 09/21/2010
• Published: 03/31/2011
• Est. Priority Date: 09/30/2009
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Ootaka, Kouji
• Granted Patent: US 8,269,512 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 21/01532 using electric or capacitive field sensors

Abstract

A capacitive occupant sensor for detecting an occupant sitting on a seat cushion of a seat of a vehicle includes a capacitive sensor mat, a cushion member, and a floating electrode. The capacitive sensor mat is disposed in the seat cushion and has a surface. The cushion member is disposed on the surface of the capacitive sensor mat. The floating electrode is disposed on an opposite side of the cushion member from the surface of the capacitive sensor mat. A projected area of the floating electrode with respect to the surface is smaller than the surface. The floating electrode is in an electrically-floating state with respect to the capacitive sensor mat. The occupant is detected based on an occupant capacitance between the capacitive sensor mat and the occupant and a floating capacitance between the capacitive sensor mat and the floating electrode.

Claims

1. A capacitive occupant sensor for detecting an occupant sitting on a seat cushion of a seat of a vehicle, the capacitive occupant sensor comprising:

a capacitive sensor mat disposed in the seat cushion and having a surface;

a cushion member disposed on the surface of the capacitive sensor mat; and

a floating electrode disposed on an opposite side of the cushion member from the surface of the capacitive sensor mat, wherein;

a projected area of the floating electrode with respect to the surface of the capacitive sensor mat is smaller than the surface of the capacitive sensor mat;

the floating electrode is in an electrically-floating state with respect to the capacitive sensor mat; and

the occupant is detected based on an occupant capacitance between the capacitive sensor mat and the occupant and a floating capacitance between the capacitive sensor mat and the floating electrode.

2. The capacitive occupant sensor according to claim 1, wherein:

the surface of the capacitive sensor mat has a center line;

the center line divides the surface of the capacitive sensor mat in half in a left-right direction of the vehicle and extends in a front-rear direction of the vehicle that is perpendicular to the left-right direction;

the surface of the capacitive sensor mat includes a front portion adjacent to a front end of the surface; and

the cushion member and the floating electrode are disposed above the front portion and are disposed above the center line.

3. The capacitive occupant sensor according to claim 1, wherein:

the surface of the capacitive sensor mat has a center line;

the center line divides the surface of the capacitive sensor mat in half in a left-right direction of the vehicle and extends in a front-rear direction of the vehicle that is perpendicular to the left-right direction;

the surface of the capacitive sensor mat includes a front portion adjacent to a front end of the surface; and

the cushion member and the floating electrode are disposed above the front portion and are disposed adjacent to the center line.

4. The capacitive occupant sensor according to claim 1, further comprising another floating electrode disposed above the capacitive sensor mat.

5. The capacitive occupant sensor according to claim 1, wherein the capacitive sensor mat includes:

a main film made of an electrical insulating material;

a cover film made of an electrical insulating material and disposed on a side of the main film;

a resist coat disposed on an opposite side of the main film from the cover film;

a first electrode disposed between the cover film and the main film;

a second electrode disposed between the cover film and the main film and being apart from the first electrode; and

a guard electrode disposed between the main film and the resist coat and being opposite to the first electrode through the main film.

6. A capacitive occupant detection apparatus comprising the capacitive occupant sensor according to claim 1 and an occupant detection device, wherein:

the capacitive occupant sensor outputs an impedance to the occupant detection device in accordance with the occupant capacitance and the floating capacitance;

the occupant detection device stores a first threshold value and a second threshold value larger than the first threshold value;

the occupant detection device determines an inflation of an airbag when the impedance is greater than the first threshold value;

the occupant detection device determines that the occupant is a small adult when the impedance is between the first threshold value and the second threshold value; and

the occupant detection device determines that the occupant is a large adult when the impedance is greater than the second threshold value.