CAPACITANCE TYPE OCCUPANT DETECTION SENSOR

• US 20140285223A1
• Filed: 02/04/2014
• Published: 09/25/2014
• Est. Priority Date: 03/21/2013
• Status: Abandoned Application

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Inoue, Takashi
• Application Number:
  US14/172,094
• Publication Number:
  US 20140285223A1
• Time in Patent Office: Days
• US Class Current: 324/688
• 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 21/015 including means for detecting the presence or position of passengers, passenger seats or child seats , and the related safety parameters therefor, e.g. speed or timing of airbag inflation in relation to occupant position or seat belt use
• CPC Class Codes: G01D 5/24 by varying capacitance

Abstract

A capacitance type occupant detection sensor includes a capacitive sensor, a reference electrode, a voltage application part, a current detector, a capacitance calculator, and a determination part. The capacitive sensor has a main electrode and is placed to a vehicle seat. The reference electrode is applied with reference voltage. The voltage application part applies detection voltage to the main electrode. The current detector detects detection current flowing through the main electrode. The capacitance calculator calculates a first capacitance between the main electrode and the reference electrode. The determination part determines an occupant of a vehicle. The capacitive sensor has a sub electrode. The determination part switches between an occupant detection mode and a wet detection mode. The capacitance calculator calculates first conductance, a second conductance, and a third conductance. The determination part determines whether the occupant exists and whether the vehicle seat is wet.

Claims

1. A capacitance type occupant detection sensor comprising:

a capacitive sensor that has a main electrode and is placed to a vehicle seat;

a reference electrode that is applied with a reference voltage;

a voltage application part that applies a detection voltage to the main electrode;

a current detector that detects a detection current flowing through the main electrode;

a capacitance calculator that calculates a first capacitance including a capacitance between the main electrode and the reference electrode, based on the detection voltage and the detection current; and

a determination part that determines an occupant on the vehicle seat based on the first capacitance,

wherein the capacitive sensor has a sub electrode that is placed apart from the main electrode in parallel,

wherein the determination part switches between an occupant detection mode and a wet detection mode,

wherein the sub electrode, in the occupant detection mode, is applied with the detection voltage,

wherein the sub electrode, in the wet detection mode, is applied with the reference voltage,

wherein the capacitance calculator, in the wet detection mode, calculates a first conductance including a conductance between the main electrode and the sub electrode, based on the detection voltage and the detection current,

wherein the capacitance calculator, in the occupant detection mode, calculates a second conductance including another conductance between the main electrode and the reference electrode, based on the detection voltage and the detection current,

wherein the capacitance calculator calculates a third conductance, which is obtained by subtracting the second conductance from the first conductance, and

wherein the determination part determines whether the occupant exists and whether the vehicle seat is wet, based on the first capacitance and the third conductance.

2. The capacitance type occupant detection sensor according to claim 1,

wherein the capacitive sensor has a guard electrode,

wherein the guard electrode is opposed to the main electrode, and

wherein the guard electrode is applied with the detection voltage.

3. The capacitance type occupant detection sensor according to claim 1,

wherein the occupant detection mode and the wet detection mode provide a detection set, and

wherein the detection set is executed at predetermined intervals.

4. The capacitance type occupant detection sensor according to claim 1,

wherein an adult person corresponds to the occupant other than a child sitting on a child restraint system, and

wherein the determination part stores:

an adult threshold value to determine whether the adult person is seated; and

a wet threshold value to determine whether the vehicle seat is wet.

5. The capacitance type occupant detection sensor according to claim 1,

wherein the capacitive sensor, which is placed to the vehicle seat, is substantially parallel to a surface of the vehicle seat.

6. The capacitance type occupant detection sensor according to claim 5,

wherein the capacitive sensor further includes film members,

wherein the main electrode and the sub electrode are placed between a first film member and a second film member, and

wherein the guard electrode is placed between the second film member and a third film member.

7. The capacitance type occupant detection sensor according to claim 6,

wherein the determination part controls two switches, which are connected to the voltage application part, the sub electrode, and a grounding, and

wherein, based on a connection state of the two switches, either the occupant detection mode or the wet detection mode is performed.