Methods and apparatus for capacitively detecting key motion and finger presence on a magnetic keyboard key

Patent metadata

Field	Value
Publication number	US-2016308531-A1
Application number	US-201615193808-A
Country	US
Kind code	A1
Filing date	Jun 27, 2016
Priority date	Jan 4, 2013
Publication date	Oct 20, 2016
Grant date	—

Abstract

Devices and methods for capacitively sensing key cap position during the initial and latter stages of a keystroke. A key assembly includes a stationary key guide magnet, a movable key cap magnet, and a transmitter/receiver electrode pair. One or both of the electrodes underlies the key cap. The capacitance change between the electrodes during a keystroke includes the capacitance change between the key cap and the electrode pair, and the change in capacitance between the key cap and the key guide. Key cap position may thus be accurately detected throughout the entire keystroke.

First claim

1 .- 6 . (canceled)

7 . A key assembly for use in a keyboard, the assembly comprising:
a key guide including a first magnetic component; a keycap including a second magnetic component and configured to be pressed downwardly relative to the key guide; and a first keystroke sensor configured to measure a variable capacitance affected by a change in a capacitive coupling between the first and second magnetic components occurring during a keystroke.

8 . The key assembly of claim 7 , wherein the first keystroke sensor comprises a transmitter electrode and a receiver electrode, wherein at least one of the transmitter electrode and the receiver electrode is disposed underneath the keycap.

9 . The key assembly of claim 7 , wherein one of a transmitter electrode and a receiver electrode is disposed underneath the keycap, and one of the transmitter electrode and receiver electrode is disposed underneath the key guide.

10 . The key assembly of claim 7 , wherein the first keystroke sensor comprises a transmitter electrode, wherein the transmitter electrode comprises a second keystroke sensor of a second key assembly.

11 . The key assembly of claim 7 , wherein the variable capacitance comprises a first capacitance between the first and second magnetic components, and a second capacitance between the first keystroke sensor and the second magnetic component.

12 . The key assembly of claim 11 , wherein the first capacitance decreases during a downward keystroke, and wherein the second capacitance increases during the downward keystroke.

13 . A method of detecting keystroke motion of a keyboard keycap responsive to applied force by an input object, the method comprising:
determining the keystroke motion based on changes in a first capacitance and a second capacitance; wherein the first capacitance is formed between a stationary key guide and the keycap, and the second capacitance is formed between a stationary keystroke sensor and the keycap.

14 . The method of claim 13 , wherein the first and second capacitances each comprises a variable capacitance.

15 . The method of claim 13 , wherein the stationary keystroke sensor comprises a transmitter and receiver electrode pair, wherein at least one of the transmitter and receiver electrodes is disposed underneath the keycap.

16 . The method of claim 13 , wherein the first capacitance decreases with downward motion of the keycap.

17 . The method of claim 13 , wherein the second capacitance increases with downward motion of the keycap.

18 . The method of claim 13 , wherein determining the keystroke motion based on changes in the first capacitance and the second capacitance comprises measuring a composite third capacitance.

19 . The method of claim 13 , wherein a transmitter electrode is configured to sense keystrokes of a plurality of keyboard keycaps.

20 . The method of claim 13 , further comprising imparting vertical and lateral motion to the keycap during the keystroke.

21 . A processing system for detecting a keystroke motion of a keyboard keycap, the processing system comprising:
circuitry configured to be communicatively coupled to a plurality of key assemblies of a keyboard, the plurality of key assemblies comprising the keyboard keycap, wherein the circuitry is configured to:
determine the keystroke motion based on changes in a first capacitance and a second capacitance,
wherein the first capacitance is formed between a stationary key guide and the keyboard keycap, and the second capacitance is formed between a stationary keystroke sensor and the keyboard keycap.

22 . The processing system of claim 21 , wherein the first capacitance and the second capacitance each comprise a variable capacitance.

23 . The processing system of claim 21 , wherein the stationary keystroke sensor comprises a transmitter and receiver electrode pair, wherein at least one of the transmitter and receiver electrode is disposed underneath the keyboard keycap.

24 . The processing system of claim 21 , wherein the first capacitance decreases with a downward motion of the keyboard keycap.

25 . The processing system of claim 21 , wherein the second capacitance increases with a downward motion of the keyboard keycap.

26 . The processing system of claim 21 , wherein the keystroke motion is determined based on change in the first capacitance and the second capacitance by measuring a composite third capacitance comprising the first and second capacitances in series.

Assignees

• Synaptics Inc

Inventors

• Bolender Robert J
• Reynolds Joesph Kurth

Classifications

• H03K17/9622 Primary

  using a plurality of detectors, e.g. keyboard · CPC title

• H01H3/122

  with enlarged actuating area, e.g. of the elongated bar-type; Stabilising means therefor · CPC title

• H01H2217/01

  Off centre actuation · CPC title

• G06F3/0202

  Constructional details or processes of manufacture of the input device · CPC title

• H03K17/98

  having a plurality of control members, e.g. keyboard · CPC title