Force detector

• US 20030030452A1
• Filed: 12/17/2001
• Published: 02/13/2003
• Est. Priority Date: 08/10/2001
• Status: Active Grant

• Current Assignee: Wacoh Company
• Original Assignee: Wacoh Company
• Inventors: Taniguchi, Nobumitsu, Okada, Kazuhiro
• Granted Patent: US 6,809,529 B2
• Time in Patent Office: Days
• US Class Current: 324/681
• CPC Class Codes: G01L 1/142 using capacitors
• CPC Class Codes: G01L 5/165 using variations in capacitance
• CPC Class Codes: G01L 5/223 to joystick controls
• CPC Class Codes: H01H 2205/024 Means to facilitate positioning
• CPC Class Codes: H01H 2239/006 Containing a capacitive switch or usable as such
• CPC Class Codes: H01H 2239/078 Variable resistance by variable contact area or point
• CPC Class Codes: H01H 2300/022 Application wake up; switches or contacts specially provided for the wake up or standby shift of a circuit
• CPC Class Codes: H01H 25/041 having a generally flat operating member depressible at different locations to operate different controls
• CPC Class Codes: H03K 17/975 using a capacitive movable element

Abstract

The invention provides a force detector in which power consumption is suppressed. Four electrodes E11 through E14 are formed on a substrate, and an elastic deformable body formed of a rubber film is disposed thereon. A conductive coating is applied on the lower surface of the elastic deformable body to provide a displacing conductive layer 26. Four capacitance elements C11 through C14 are comprised by the electrodes E11 through E14 and the displacing conductive layer 26 opposed to the electrodes. The capacitance values thereof are converted into voltage values V11 through V14 by C/V converter circuit 50, and based on operation by signal processing circuit 60, an external force applied to the elastic deformable body is detected. A pair of contacting electrodes E15 and E16 are formed on the substrate, and when an external force with a predetermined strength or more is applied, the elastic deformable body deforms, and the displacing conductive layer 26 comes into contact with both electrodes E15 and E16, simultaneously. The potential of the electrode E16 is taken-in from the terminal T5, and when said potential is Vcc, the C/V converter circuit 50 is operated in a standby mode with less power consumption, and when said potential is GND, the circuit is operated in a normal mode.

Claims

1. A force detector having a function for detecting a strength of an applied external force, comprising:

a substrate;

an elastic deformable body which is disposed at a position opposed to the substrate, at least a portion of said elastic deformable body being made of material having elastic deformability, and said elastic deformable body displacing with respect to the substrate due to an elastic deformation caused by the applied external force;

a force detecting element disposed between said substrate and said elastic deformable body and changes in a predetermined electrical characteristic due to a displacement of said elastic deformable body;

a switching element including a pair of contacting electrodes and carrying out a switching function so that an electrical insulated condition is normally maintained between said pair of contacting electrodes, and when an external force with more than a predetermined strength is applied to said elastic deformable body, an electrical conductive condition is obtained between said pair of contacting electrodes in response to a deformation of said elastic deformable body; and

a detection circuit for detecting a change in said electrical characteristic of said force detecting element as an electric signal;

wherein said detection circuit selectively operates in two modes of a detection mode and a standby mode, said detection circuit performing a detecting function for outputting a change in said electrical characteristic as an electric signal when said detection circuit operates in said detection mode, said detection circuit maintaining a standby condition waiting for a transition to said detection mode without performing the detecting function when said detection circuit operates in said standby mode, a power consumption in said standby mode being less than a power consumption in said detection mode; and

wherein said standby mode is selected when an electrical condition between said pair of contacting electrodes is an insulated condition, and said detection mode is selected when an electrical condition between said pair of contacting electrodes is a conductive condition.

2. A force detector according to claim 1:

wherein the pair of contacting electrodes included in the switching element are comprised of a contacting fixed electrode disposed on the substrate and a contacting displacing electrode disposed on the elastic deformable body, and when an external force with more than the predetermined strength is applied to the elastic deformable body, due to a deformation of the elastic deformable body, said contacting displacing electrode comes into physical contact with said contacting fixed electrode.

3. A force detector according to claim 1:

wherein the switching element includes a pair of contacting electrodes disposed on the substrate and a mediating electrode which simultaneously comes into contact with both of said pair of contacting electrodes to make an electrical conductive condition between said pair of contacting electrodes, and

wherein said mediating electrode is disposed so that said mediating electrode is normally maintained to be contacted with neither of said pair of contacting electrodes, or contacted with either one of said pair of contacting electrodes, and when an external force with more than the predetermined strength is applied to the elastic deformable body, due to a deformation of the elastic deformable body, said mediating electrode simultaneously comes into contact with both of said pair of contacting electrodes.

4. A force detector according to claim 3:

wherein the mediating electrode is formed at a position at which a deformation of the elastic deformable body occurs.

5. A force detector according to claim 4:

wherein the pair of contacting electrodes are comprised of a first ring-shaped electrode and a second ring-shaped electrode disposed adjacent to and outside the first ring-shaped electrode, and

the mediating electrode is disposed at a position so as to be able to be simultaneously contacted with both said first ring-shaped electrode and said second ring-shaped electrode at any position.

6. A force detector according to claim 4:

wherein the pair of contacting electrodes are comprised of a plural number N of electrodes belonging to a first group and a plural number N of electrodes belonging to a second group which are arranged on the substrate so that the i-th electrode (1≦

i≦

N) belonging to the first group and the i-th electrode belonging to the second group are adjacent to each other, a pair of contacting electrodes are formed of an electrode belonging to the first group and an electrode belonging to the second group which are adjacent to each other, and a total of N pairs of contacting electrodes are provided.

7. A force detector according to claim 6:

wherein electrodes belonging to the first group and electrodes belonging to the second group are alternately disposed along a circumference defined on the substrate, and

the mediating electrode is disposed along a circumference on the elastic deformable body opposed to said circumference defined on the substrate.

8. A force detector according to claim 3:

wherein a domed structure is provided and disposed turned down in a vicinity of the pair of contacting electrodes on the substrate, said domed structure having a property whereby a vicinity of an apex elastically deforms to be convexed downward when a downward pressing force with more than predetermined strength is applied to a vicinity of said apex, and having a conductive contacting surface which is used as a mediating electrode so that, when an external force with more than the predetermined strength is applied to the elastic deformable body, a shape of said domed structure is inverted due to a deformation of the elastic deformable body, and said conductive contacting surface simultaneously comes into contact with both of the pair of contacting electrodes.

9. A force detector according to claim 8:

wherein the mediating electrode is comprised of a conductive contacting surface which extends from a lower surface part of an apex of the domed structure to a bottom circumferential part of the domed structure, a first electrode among the pair of contacting electrodes being disposed at a position to be contacted with said bottom circumferential part of the domed structure, a second electrode among the pair of contacting electrodes being disposed at a center of the domed structure, and

wherein said mediating electrode normally maintains a contacted condition with only said first electrode, and simultaneously comes into contact with both of said first electrode and said second electrode due to a shape inversion of the domed structure when an external force with more than the predetermined strength is applied to the elastic deformable body.

10. A force detector according to claim 8:

wherein the pair of contacting electrodes are disposed in a region surrounded by a bottom circumferential surface of the domed structure, the mediating electrode comprised of a conductive contacting surface formed on a lower surface of an apex of the domed structure normally maintains non-contact condition to be contacted with neither of the pair of contacting electrodes, and when an external force with more than the predetermined strength is applied to the elastic deformable body, the mediating electrode simultaneously comes into contact with both of the pair of contacting electrodes due to a deformation of the elastic deformable body.

11. A force detector according to claim 1:

wherein a capacitance element is used as a force detecting element, and the detection circuit detects a capacitance value of said capacitance element as an electric signal, said capacitance element comprising a detecting fixed electrode provided on the substrate and a detecting displacing electrode provided at a position on the elastic deformable body which is opposed to said detecting fixed electrode and at which a displacement occurs.

12. A force detector according to claim 3:

wherein a capacitance element is used as a force detecting element, and the detection circuit detects a capacitance value of said capacitance element as an electric signal, said capacitance element comprising a detecting fixed electrode provided on the substrate and a detecting displacing electrode provided at a position on the elastic deformable body which is opposed to said detecting fixed electrode and at which a displacement occurs, the mediating electrode and said detecting displacing electrode being electrically connected, and the detection circuit has a function for detecting a capacitance value between a contacting electrode which is contacted with the mediating electrode and said detecting fixed electrode as a capacitance value of the capacitance element in the detection mode.

13. A force detector according to claim 3:

wherein a capacitance element is used as a force detecting element, and the detection circuit detects a capacitance value of said capacitance element as an electric signal, said capacitance element comprising a detecting fixed electrode provided on the substrate and a detecting displacing electrode provided at a position on the elastic deformable body which is opposed to said detecting fixed electrode and at which a displacement occurs,

wherein a domed structure is provided and disposed turned down in a vicinity of the pair of contacting electrodes on the substrate, said domed structure having a property whereby a vicinity of an apex elastically deforms to be convexed downward when a downward pressing force with more than predetermined strength is applied to a vicinity of said apex, and having a conductive contacting surface which is used as a mediating electrode so that, when an external force with more than the predetermined strength is applied to the elastic deformable body, a shape of said domed structure is inverted due to a deformation of the elastic deformable body, and said conductive contacting surface simultaneously comes into contact with both of the pair of contacting electrodes, and

wherein at least an upper surface and a lower surface of a vicinity part of an apex of said domed structure are comprised of a conductive material and are electrically connected with each other, amediating conductive layer electrically connected to said detecting displacing electrode is formed at a portion of the elastic deformable body to be contacted with a vicinity part of the apex of the domed structure, and the detection circuit has a function for detecting a capacitance value between one of said pair of contacting electrodes which is electrically contacted with said mediating conductive layer via the domed structure and said detecting fixed electrode as a capacitance value of the capacitance element in the detection mode.

14. A force detector according to claim 11:

wherein on a surface of at least either one of the detecting fixed electrode and the detecting displacing electrode, an insulating film is formed to prevent an electrical contact between said detecting fixed electrode and said detecting displacing electrode.

15. A force detector according to claim 11:

wherein the detection circuit has a C/V converter circuit for converting a capacitance value C of the capacitance element into a voltage value V, and a control is carried out so that said C/V converter circuit is operated in the detection mode and is not operated in the standby mode.

16. A force detector according to claim 15:

wherein the C/V converter circuit comprises an oscillation circuit for supplying an AC signal to one of the electrodes comprising the capacitance element, and a switching circuit which causes said oscillation circuit to oscillate in the detection mode, and stop an oscillation of said oscillation circuit in the standby mode.

17. A force detector according to claim 11:

wherein the detection circuit has a C/f converter circuit for converting a capacitance value C of the capacitance element into a frequency f, and control is carried out so that said C/f converter circuit is operated in the detection mode and is not operated in the standby mode.

18. A force detector according to claim 11:

wherein the detecting displacing electrode is comprised of a conductive coating layer applied on a surface of an integrally molded rubber.

19. A force detector according to claim 1:

wherein a variable resistance element with a property by which a resistance value between two predetermined points changes depending on an applied pressure is used as a force detecting element, and the detection circuit detects a resistance value between said two points of said variable resistance element as an electric signal.

20. A force detector according to claim 19:

wherein a variable resistance element has a first resistor and a second resistor disposed at a position opposed to the first resistor, and a surface of at least one resistor of the first and second resistors, which is opposed to the other resistor, has an uneven structure to elastically deform, and a contact surface area between the first resistor and the second resistor changes in accordance with a pressure applied in response to an applied external force which is a detecting subject so that a resistance value between a predetermined point connected to the first resistor and a predetermined point connected to the second resistor changes in accordance with changes in said contact surface area.

21. A force detector according to claim 20:

wherein the first resistor and the second resistor are formed from a sensitive conductive ink.

22. A force detector according to claim 20:

wherein the detection circuit has a circuit for detecting a resistance value between the two points of the resistors by applying a voltage between said two points, and control is carried out so that the voltage is applied in the detection mode and is not applied in the standby mode.

23. A force detector according to claim 22:

wherein an electrical conductive/insulated condition between the pair of contacting electrodes comprising a switching element is used as an ON/OFF switch to apply a voltage to the two points of the resistors.

24. A force detector according to claim 1:

wherein an operation panel made of a rigid material is attached to the elastic deformable body, and the elastic deformable body deforms based on an operational input applied to said operation panel.

25. A force detector according to claim 1:

wherein the elastic deformable body comprises a film portion disposed almost in parallel to an upper surface of the substrate, a side wall portion for fixing a surrounding of said film portion to said upper surface of the substrate, and columnar projections extending downward from a plurality of positions of a lower surface of said film portion, at least a part of said film portion and said columnar projections being made of elastic material.

26. A force detector according to claim 25:

wherein the elastic deformable body is made of an integrally-molded rubber.

27. An input device for an electronic apparatus for applying operational input indicating an operation amount in a predetermined direction to the electronic apparatus which executes particular processing based on a predetermined program, wherein said input device comprises a force detector according to claim 1, and handles an external force detected by the force detector as an operation amount.