Human body detector

• US 6,774,789 B2
• Filed: 08/10/2001
• Issued: 08/10/2004
• Est. Priority Date: 08/11/2000
• Status: Expired due to Fees

• Current Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.), Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.), Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Murakami, Yuichi, Okada, Hiroki, Ieda, Kiyokazu, Mushiake, Eiji, Inaba, Hisashi
• Primary Examiner(s): Hofsass, Jeffery
• Assistant Examiner(s): NGUYEN, HUNG T
• Application Number:
  US09/925,308
• Publication Number:
  US 20020030594A1
• Time in Patent Office: 1,096 Days
• Field of Search: 340/541, 340/426, 340/562, 340/602, 340/573.1, 340/576, 340/5.53, 340/567, 340/568.1
• US Class Current: 340/541
• CPC Class Codes: B60R 25/246 characterised by the challenge triggering
• CPC Class Codes: G07C 2209/64 using a proximity sensor

Abstract

In a human body detector, a wave-detection circuit for detecting waves of a resonance voltage is connected to a sensor resonance circuit that varies a constant frequency voltage in accordance with a change in the capacitance of a sensor electrode. The wave-detection circuit is connected to a differentiator that acquires a changing rate by differentiating the wave-detection voltage with respect to time, and allows a voltage to pass if the changing rate of the voltage is greater than or equal to a predetermined value. The differentiator is connected to a high-pass filter that allows passage of a voltage whose changing rate is greater than or equal to a second predetermined value. The high-pass filter is connected to a comparator whose non-inversion input terminal is connected to a power source that applies thereto a reference voltage.

Claims

1. A human body detector comprising:

a capacitance-type sensor that a human body contacts or approaches, the capacitance-type sensor including a sensor resonance circuit and a wave detector circuit;

detection means for receiving an output of the capacitance-type sensor, and distinguishing between the human body from a raindrop and detecting only the human body based on a change in the output within a predetermined time, the detection means including a band-pass filter, the band-pass filter including a differentiator, a high-pass filter and a comparator; and

wherein the sensor resonance circuit has a sensor electrode supplied with a constant frequency voltage and outputs a resonance voltage integrated the constant frequency voltage with respect to a capacitance of an object that contacts to the sensor electrode, the wave detector circuit outputs a wave detection voltage obtained through wave detection and conversion of the resonance voltage, and the differentiator differentiates the wave detection voltage with respect to time to acquire the changing rate.

2. A human body detector according to claim 1, wherein the detection means allows a voltage to pass if a changing rate of the output is in a predetermined band.

3. A human body detector according to claim 1, wherein the human body detector is disposed in a door handle of a motor vehicle, and detects a contact between the door handle and the human body.

4. A human body detector according to claim 1, wherein the human body detector is installed in a vehicle-installed apparatus of a smart entry system.

5. A human body detector according to claim 1, wherein the capacitance-type sensor includes a sensor resonance circuit and a wave detector circuit.

6. A human body detector according to claim 1, wherein the high-pass filter permits passage of a wave detection voltage if a changing rate of the wave detection voltage exceeds a predetermined voltage after passage of 5 msec.

7. A human body detector according to claim 1, wherein the differentiator permits passage of a wave detection voltage if a changing rate of the wave detection voltage exceeds a predetermined voltage within 50 msec.

8. A human body detector according to claim 1, wherein the high-pass filter excludes a relatively sharp changing rate of voltage while the differentiator excludes a relatively gentle changing rate of voltage.