Capacitive occupancy detector apparatus

• US 4,796,013 A
• Filed: 10/15/1986
• Issued: 01/03/1989
• Est. Priority Date: 10/18/1985
• Status: Expired due to Term

• Current Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.)
• Original Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.)
• Inventors: Ohashi, Masao, Yasuda, Tomio, Sato, Jun
• Primary Examiner(s): Swann, III, Glen R.
• Application Number:
  US06/919,272
• Time in Patent Office: 811 Days
• Field of Search: 340/562, 340/568, 340/540, 340/52 E, 340/52 D, 340/939, 340/677, 180/272, 307/10 SB, 307/10 R, 307/125, 307/116
• US Class Current: 340/562
• CPC Class Codes: G01V 3/088 operating with electric fields G01V3/082 takes precedence
• CPC Class Codes: G07B 13/04 for indicating fare or state of hire
• CPC Class Codes: H01H 3/141 Cushion or mat switches
• CPC Class Codes: H03K 17/955 using a capacitive detector

Abstract

A capacitive occupancy detector apparatus includes a personnel containment device having first and second electrodes which will define an electric field therebetween which will be intercepted by a person present in the containment device. A detecting device is provided for detecting the capacitance formed between the first and second electrodes and a processor is provided for storing the capacitance at predetermined periods. The difference between the last capacitance detected and a capacitance previously stored is detected to determine the presence of a person when the difference indicates an increase of the capacitance exceeding a first predetermined threshold. A second threshold is set based upon the capacitance which determines the presence of a person so that the subsequent determination of the absence of a person is based upon detecting a decrease of the capacitance with respect to the second threshold.

Claims

1. A personnel detector comprising

personnel containment means

first and second electrodes insulated from each other and arranged such that at least part of a person present in said personnel containment means is disposed therebetween;

capacitance detecting means for detecting a capacitance between the first and the second electrodes and providing a representative electrical signal;

processing means including storage means for storing the electrical signal;

storage update means for causing the electrical signal stored in the storage means to be updated at given time intervals;

comparison means for producing an electrical signal representing the arrival of a person whenever a difference between the electrical signal developed by the capacitance detecting means and the signal stored by the storage means exceeds a first threshold value; and

means for setting a second threshold value based on the capacitance detected during the presence of a person and determining the departure of a person when the capacitance detected by the detecting means decreases below said second threshold value;

wherein said capacitance detecting means includes an oscillator means which produces a signal of a frequency which decreases with an increasing capacitance and a frequency/voltage converter.

2. A personnel detector according to claim 1 in which the electrical signal developed by the capacitance detecting means comprises a voltage signal which corresponds to the frequency developed by the oscillator means.

3. A personnel detector according to claim 2 in which the storage means comprises means for retaining a sample voltage.

4. A personnel detector according to claim 3 in which the storage update means comprises means for producing a sampling signal which is applied to the sample voltage retaining means to sample the voltage, further including blocking means for preventing a sampling signal from being produced whenever the comparison and processing means produces an electrical signal representing the presence of a person.

5. A personnel detector comprising

personnel containment means

first and second electrodes insulated from each other and arranged such that at least part of a person present in said personnel containment means is disposed therebetween;

capacitance detecting means for detecting a capacitance between the first and the second electrodes and providing a representative electrical signal;

processing means including storage means for storing the electrical signal;

storage update means for causing the electrical signal stored in the storage means to be updated at given time intervals;

comparison means for producing an electrical signal representing the arrival of a person whenever a difference between the electrical signal developed by the capacitance detecting means and the signal stored by the storage means exceeds a first threshold value; and

means for setting a second threshold value based on the capacitance detected during the presence of a person and determining the departure of a person when the capacitance detected by the detecting means decreases below said second threshold value;

wherein the first electrode comprises a conductive layer mounted on a door trim of the vehicle and the second electrode comprises the body of the vehicle.

6. A personnel detector according to claim 5 in which the conductive layer is in the form of a thin film of electrically conductive material such as a metal foil, a fabric of conductive fibers, a conductive paint applied to a film or the like.

7. A personnel detector according to claim 6 in which the conductive layer is mounted on the rear side of a skin of the door trim.

8. A personnel detector comprising

personnel containment means

first and second electrodes insulated from each other and arranged such that at least part of a person present in said personnel containment means is disposed therebetween;

capacitance detecting means for detecting a capacitance between the first and the second electrodes and providing a representative electrical signal;

processing means including storage means for storing the electrical signal;

storage update means for causing the electrical signal stored in the storage means to be updated at given time intervals;

comparison means for producing an electrical signal representing the arrival of a person whenever a difference between the electrical signal developed by the capacitance detecting means and the signal stored by the storage means exceeds a first threshold value; and

means for setting a second threshold value based on the capacitance detected during the presence of a person and determining the departure of a person when the capacitance detected by the detecting means decreases below said second threshold value;

wherein the first electrode comprises a conductive layer mounted on an arm rest of the vehicle and the second electrode comprises the body of the vehicle.

9. A personnel detector according to claim 8 in which the conductive layer is in the form of a thin film of electrically conductive material such as a metal foil, a fabric of conductive fibers, a conductive paint applied to a film or the like.

10. A personnel detector according to claim 9 in which the conductive layer is mounted on the rear side of a skin of the arm rest.

11. A personnel detector comprising

personnel containment means

first and second electrodes insulated from each other and arranged such that at least part of a person present in said personnel containment means is disposed therebetween;

capacitance detecting means for detecting a capacitance between the first and the second electrodes and providing a representative electrical signal;

processing means including storage means for storing the electrical signal;

storage update means for causing the electrical signal stored in the storage means to be updated at given time intervals;

comparison means for producing an electrical signal representing the arrival of a person whenever a difference between the electrical signal developed by the capacitance detecting means and the signal stored by the storage means exceeds a first threshold value; and

means for setting a second threshold value based on the capacitance detected during the presence of a person and determining the departure of a person when the capacitance detected by the detecting means decreases below said second threshold value;

wherein the first electrode comprises a conductive layer mounted on a floor mat of the vehicle and covering a major portion of the floor mat and the second electrode comprises the body of the vehicle.

12. A personnel detector according to claim 11 in which the conductive layer is in the form of a thin film of a electrically conductive material such as a metal foil, a fabric of conductive fibers, a conductive paint applied to a film or the like.