VARIABLE CAPACITOR AND POSITION INDICATOR

• US 20110241703A1
• Filed: 03/24/2011
• Published: 10/06/2011
• Est. Priority Date: 03/31/2010
• Status: Active Grant

• Current Assignee: Wacom Co Limited (Wacom)
• Original Assignee: Wacom Co Limited (Wacom)
• Inventors: Fukushima, Yasuyuki, Fujitsuka, Hiroyuki
• Granted Patent: US 8,525,530 B2
• Time in Patent Office: Days
• US Class Current: 324/662
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: H01G 5/16 using variation of distance between electrodes

Abstract

A variable capacitor is disclosed, including: a dielectric having a first surface and a second surface opposing the first surface; a first electrode disposed on the first surface of the dielectric; a second electrode disposed to face the second surface of the dielectric; and a pressing member configured to cause the second electrode and the dielectric to contact each other when a pressing force is applied thereto (e.g., when a pen-shaped position indicator including the variable capacitor is pressed against a tablet). In the variable capacitor, the second electrode includes at least one electrode piece having an abutting central portion, against which the pressing member transmits a pressing force applied thereto, and an extension portion that radially extends from the abutting central portion toward a circumferential portion of the dielectric. A contact area between the dielectric and the second electrode is changed in accordance with a pressing force applied to the pressing member, to thereby change a capacitance of the variable capacitor.

Claims

1. A variable capacitor, comprising:

a dielectric having a first surface and a second surface opposing said first surface;

a first electrode disposed on said first surface of said dielectric;

a second electrode disposed to face said second surface of said dielectric; and

a pressing member configured to cause said second electrode and said dielectric to contact each other when a pressing force is applied thereto,

wherein said second electrode includes at least one electrode piece having an abutting central portion, against which said pressing member transmits a pressing force applied thereto, and an extension portion that radially extends from said abutting central portion toward a circumferential portion of said dielectric; and

the variable capacitor is configured such that a contact area between said dielectric and said second electrode is changed in accordance with a pressing force applied to said pressing member, to change a capacitance of the variable capacitor.

2. The variable capacitor according to claim 1, wherein said second electrode is formed of a conductive elastic member and is formed into a flat plate-like shape.

3. The variable capacitor according to claim 2, wherein said second electrode has an electrode piece having a shape that is line-symmetric about a line that extends through a center of the abutting central portion.

4. The variable capacitor according to claim 3, wherein the electrode piece includes two extension portions that are line-symmetric and radially extend from the abutting central portion in opposite directions.

5. The variable capacitor according to claim 2, wherein said electrode piece has a generally fan-like shape.

6. The variable capacitor according to claim 5, wherein one or both of a width of said abutting central portion, which extends orthogonal to the radially extending direction of the electrode piece, and a central angle of said generally fan-like shape relative to the radially extending direction of the electrode piece are selectively set so as to controllably change the capacitance of the variable capacitor in accordance with a pressing force applied to said pressing member.

7. A variable capacitor, comprising:

a dielectric having a first surface and a second surface opposing said first surface;

a first electrode disposed on said first surface of said dielectric;

a second electrode disposed to face said second surface of said dielectric; and

a pressing member configured to cause said second electrode and said dielectric to contact each other when a pressing force is applied thereto,

wherein said second surface of the dielectric includes a masked portion having a smaller permittivity than that of said dielectric and an un-masked portion exposing the dielectric therethrough, the un-masked portion including an abutting central portion and an extension portion that radially extends from said abutting central portion toward a circumferential portion of said dielectric; and

the variable capacitor is configured such that a contact area between said dielectric and said second electrode is changed in accordance with a pressing force applied to said pressing member, to change a capacitance of the variable capacitor.

8. The variable capacitor according to claim 7, wherein said second electrode is formed of a conductive elastic member into an approximately columnar shape, and a portion thereof which is brought into contact with said second surface of the dielectric is formed in an approximately dome-like shape.

9. A position indicator, comprising:

a variable capacitor including;

a dielectric having a first surface and a second surface opposing said first surface;

a first electrode disposed on said first surface of said dielectric;

a second electrode disposed to face said second surface of said dielectric; and

a pressing member configured to cause said second electrode and said dielectric to contact each other when a pressing force is applied thereto, wherein said second electrode includes at least one electrode piece having an abutting central portion, against which said pressing member transmits a pressing force applied thereto, and an extension portion that radially extends from said abutting central portion toward a circumferential portion of said dielectric; and

wherein the variable capacitor is configured such that a contact area between said dielectric and said second electrode is changed in accordance with a pressing force applied to said pressing member, to change a capacitance of the variable capacitor; and

a resonance circuit having said variable capacitor as a circuit element.

10. A position indicator, comprising:

a variable capacitor including;

a dielectric having a first surface and a second surface opposing said first surface;

a first electrode disposed on said first surface of said dielectric;

a second electrode disposed to face said second surface of said dielectric; and

a pressing member configured to cause said second electrode and said dielectric to contact each other when a pressing force is applied thereto, wherein said second surface of the dielectric includes a masked portion having a smaller permittivity than that of said dielectric and an un-masked portion exposing the dielectric therethrough, the un-masked portion including an abutting central portion and an extension portion that radially extends from said abutting central portion toward a circumferential portion of said dielectric; and

wherein the variable capacitor is configured such that a contact area between said dielectric and said second electrode is changed in accordance with a pressing force applied to said pressing member, to change a capacitance of the variable capacitor; and

a resonance circuit having said variable capacitor as a circuit element.

11. A position indicator, comprising:

a variable capacitor including;

a dielectric having a first surface and a second surface opposing said first surface;

a first electrode disposed on said first surface of said dielectric;

a second electrode disposed to face said second surface of said dielectric; and

a pressing member configured to cause said second electrode and said dielectric to contact each other when a pressing force is applied thereto, wherein said second electrode includes at least one electrode piece having an abutting central portion, against which said pressing member transmits a pressing force applied thereto, and an extension portion that radially extends from said abutting central portion toward a circumferential portion of said dielectric; and

wherein the variable capacitor is configured such that a contact area between said dielectric and said second electrode is changed in accordance with a pressing force applied to said pressing member, to change a capacitance of the variable capacitor; and

a resonance circuit having said variable capacitor as a circuit element; and

a pen-shaped case,

wherein said variable capacitor is disposed in the pen-shaped case such that a direction along which a pressing force is applied to the pressing member coincides with a longitudinal direction of said pen case; and

a distal tip of the pressing member protrudes from said pen case to form a pen tip.

12. A position indicator, comprising:

a variable capacitor including;

a dielectric having a first surface and a second surface opposing said first surface;

a first electrode disposed on said first surface of said dielectric;

a second electrode disposed to face said second surface of said dielectric; and

a pressing member configured to cause said second electrode and said dielectric to contact each other when a pressing force is applied thereto, wherein said second surface of the dielectric includes a masked portion having a smaller permittivity than that of said dielectric and an un-masked portion exposing the dielectric therethrough, the un-masked portion including an abutting central portion and an extension portion that radially extends from said abutting central portion toward a circumferential portion of said dielectric; and

wherein the variable capacitor is configured such that a contact area between said dielectric and said second electrode is changed in accordance with a pressing force applied to said pressing member, to change a capacitance of the variable capacitor; and

a resonance circuit having said variable capacitor as a circuit element; and

a pen-shaped case,

wherein said variable capacitor is disposed in the pen-shaped case such that a direction along which a pressing force is applied to the pressing member coincides with a longitudinal direction of said pen case; and

a distal tip of the pressing member protrudes from said pen case to form a pen tip.