Capacitive lock switch

• US 20070023265A1
• Filed: 07/27/2006
• Published: 02/01/2007
• Est. Priority Date: 07/29/2005
• Status: Abandoned Application

• Current Assignee: Stanley Electric Company Limited
• Original Assignee: Stanley Electric Company Limited
• Inventors: Hirose, Yoichi, Ishikawa, Kiyomitsu
• Application Number:
  US11/460,347
• Publication Number:
  US 20070023265A1
• Time in Patent Office: Days
• US Class Current: 200/61.620
• CPC Class Codes: E05B 81/78 as part of a hands-free locking or unlocking operation
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 2217/960715 Rc-timing; e.g. measurement of variation of charge time or discharge time of the sensor

Abstract

A capacitive lock can include various circuits that allow it to operate more efficiently and with greater accuracy. For example, when a user continuously touches a door handle for a certain time duration, a sensor can be configured to retain a variation in capacitance. When the door handle is continuously touched, a time constant circuit (timer) can be provided inside the entry system and measures the contact time and unlocks a door on the assumption that the user has a will to unlock and/or operate the vehicle or other apparatus.

Claims

1. A capacitive lock switch, comprising:

an electrode located adjacent a door handle;

a converter circuit configured to convert a variation in capacitance associated with the electrode into an electrical parameter;

a decision circuit configured to detect a level variation in the electrical parameter; and

a time constant circuit configured to measure a time of duration of the level variation in the electrical parameter and to provide a lock signal upon measurement of the variation in capacitance over a certain time duration.

2. The capacitive lock switch according to claim 1, wherein the time constant circuit is configured to determine the variation in capacitance and the time duration of the level variation in the electrical parameter through a comparison of frequencies before the variation in capacitance stored at certain time intervals with frequencies after the variation in capacitance.

3. The capacitive lock switch according to claim 1, wherein the decision circuit includes a circuit configured to detect the slope/tilt of the level variation in the electrical parameter.

4. The capacitive lock switch according to claim 1, further comprising:

a detection circuit configured to detect a beginning of the variation in capacitance; and

a second time constant circuit configured to detect time duration of the variation in capacitance in conjunction with the detection circuit.

5. The capacitive lock switch according to claim 4, wherein the second time constant circuit has a time constant of 0.3-1.5 seconds.

6. The capacitive lock switch according to claim 1, further comprising:

a circuit configured to reduce a return time until capacitance becomes detectable after capacitance becomes undetectable.

7. The capacitive lock switch according to claim 3, further comprising:

a circuit configured to reduce a return time until capacitance becomes detectable after capacitance becomes undetectable.

8. The capacitive lock switch according to claim 1, wherein the electrode is a metallic electrode.

9. A capacitive lock switch, comprising:

an electrode located adjacent a door handle;

a converter circuit configured to convert a variation in capacitance associated with the electrode into an electrical parameter;

a decision circuit configured to determine from the electrical parameter whether the electrode has been contacted by a human body; and

a time constant circuit configured to measure a time of duration of the variation in capacitance and to provide a lock signal upon both measurement of the variation in capacitance over a certain time duration and a determination from the decision circuit that the electrode has been contacted by a human body.

10. The capacitive lock switch according to claim 9, wherein the electrode is a metallic electrode.

11. The capacitive lock switch according to claim 9, wherein the time constant circuit is configured to compare frequencies before the variation in capacitance stored at certain time intervals with frequencies after the variation in capacitance.

12. The capacitive lock switch according to claim 9, wherein the decision circuit includes a circuit configured to detect the slope/tilt of variation in the electrical parameter.

13. The capacitive lock switch according to claim 9, wherein the certain time duration is between 0.3 and 1.5 seconds.