Shear force sensor, and detection unit for shear force sensor
A thin and durable detection unit for a shear force sensor is disclosed. The detection unit detects shear forces in a plurality of directions. A detection circuit is connected to a first electrode layer and a second electrode layer. First driving electrodes and second driving electrodes insulated from each other by first isolation trenches are formed in the first electrode layer. The second driving electrodes also serving as third driving electrodes and the first driving electrodes also serving as fourth driving electrodes insulated from each other by second isolation trenches are formed in the first electrode layer. First detection electrodes and second detection electrodes are formed in the second electrode layer.
1 . A shear force sensor comprising:
a first electrode layer and a second electrode layer opposite to each other;
an insulating elastic body layer that is located between the first electrode layer and the second electrode layer to electrically insulate both the electrode layers and is elastically deformable in a first in-plane direction of the first electrode layer; and
a detection circuit connected to the first electrode layer and the second electrode layer, wherein:
a first driving electrode and a second driving electrode insulated from each other by a first isolation trench are formed in the first electrode layer,
a third driving electrode and a fourth driving electrode insulated from each other by a second isolation trench are formed in the first electrode layer,
the first isolation trench has a first portion extending in a first direction in the first in- plane direction, and the second isolation trench has a second portion extending in a second direction in the first in-plane direction, the first direction and the second direction being directions crossing each other,
a first detection electrode overlapped on the first driving electrode, the first portion of the first isolation trench, and the second driving electrode when viewed in a first normal direction perpendicular to the first in-plane direction is formed in the second electrode layer,
a second detection electrode overlapped on the third driving electrode, the second portion of the second isolation trench, and the fourth driving electrode when viewed in the first normal direction is formed in the second electrode layer, and
wherein the detection circuit
detects a first shear force exerted in a first shear direction perpendicular to the first direction in the first in-plane direction based on a change in a first capacitance produced between the first driving electrode and the first detection electrode and a change in a second capacitance produced between the second driving electrode and the first detection electrode, and
detects a second shear force exerted in a second shear direction perpendicular to the second direction in the first in-plane direction based on a change in a third capacitance produced between the third driving electrode and the second detection electrode and a change in a fourth capacitance produced between the fourth driving electrode and the second detection electrode.
2 . The shear force sensor according to claim 1 , wherein the second driving electrode also serves as the third driving electrode.
3 . The shear force sensor according to claim 1 , wherein
the first portion is provided at a plurality of locations by changing a direction in which the first isolation trench extends a plurality of times, and
the first detection electrode has a shape overlapped on the first portion at the plurality of locations when viewed in the first normal direction.
4 . The shear force sensor according to claim 1 , wherein a plurality of sets of the first driving electrode, the first isolation trench, the second driving electrode, and the first detection electrode are provided.
5 . The shear force sensor according to claim 1 , wherein
the insulating elastic body layer is elastically deformable in the first normal direction, and
the detection circuit detects a pressing force in the first normal direction based on changes in the first capacitance, the second capacitance, the third capacitance, and the fourth capacitance.
6 . The shear force sensor according to claim 1 , further comprising a first insulating layer, a first shield layer, a second insulating layer, and a second shield layer, wherein
the first shield layer, the first insulating layer, the first electrode layer, the insulating elastic body layer, the second electrode layer, the second insulating layer, and the second shield layer are arranged in an order presented in the first normal direction,
the first shield layer and the second shield layer are made of sheet-like conductors respectively overlapped on whole surfaces of the first electrode layer and the second electrode layer when viewed in the first normal direction, and
the first insulating layer insulates the first electrode layer and the first shield layer, and the second insulating layer insulates the second electrode layer and the second shield layer.
7 . The shear force sensor according to claim 1 , further comprising a touch sensor overlapped on the first electrode layer in the first normal direction, wherein
the detection circuit is configured to detect a contact made by the touch sensor.
8 . The shear force sensor according to claim 1 , further comprising a wiring part that connects the detection circuit to the first electrode layer and the second electrode layer, wherein
the wiring part has a flexible portion that is easier to deform than a detection unit including the first electrode layer, the second electrode layer, and the insulating elastic body layer.
9 . The shear force sensor according to claim 1 , wherein
the first electrode layer, the second electrode layer, and the insulating elastic body layer are bent,
the insulating elastic body layer is elastically deformable also in a second in-plane direction different from the first in-plane direction,
a fifth driving electrode and a sixth driving electrode insulated from each other by a third isolation trench extending in the second in-plane direction and spreading in the second in-plane direction are formed in the first electrode layer,
the third isolation trench has a third portion extending in a third direction in the second in-plane direction,
a third detection electrode overlapped on the fifth driving electrode, the third portion of the third isolation trench, and the sixth driving electrode when viewed in a second normal direction perpendicular to the second in-plane direction is formed in the second electrode layer, and
the detection circuit detects a third shear force exerted in a third shear direction perpendicular to the third direction in the second in-plane direction based on a change in a fifth capacitance produced between the fifth driving electrode and the third detection electrode and a change in a sixth capacitance produced between the sixth driving electrode and the third detection electrode.
10 . A detection unit for a shear force sensor, comprising:
a first electrode layer and a second electrode layer opposite to each other; and
an insulating elastic body layer that is located between the first electrode layer and the second electrode layer to electrically insulate both the first and the second electrode layers and is elastically deformable in a first in-plane direction of the first electrode layer, wherein
a first driving electrode and a second driving electrode insulated from each other by a first isolation trench are formed in the first electrode layer,
a third driving electrode and a fourth driving electrode insulated from each other by a second isolation trench are formed in the first electrode layer,
the first isolation trench has a first portion extending in a first direction in the first in-plane direction, and the second isolation trench has a second portion extending in a second direction in the first in-plane direction, the first direction and the second direction being directions crossing each other,
a first detection electrode overlapped on the first driving electrode, the first portion of the first isolation trench, and the second driving electrode when viewed in a first normal direction perpendicular to the first in-plane direction is formed in the second electrode layer, and
a second detection electrode overlapped on the third driving electrode, the second portion of the second isolation trench, and the fourth driving electrode when viewed in the first normal direction is formed in the second electrode layer.
11 . The detection unit of claim 10 , wherein the detection unit is configured to
detect a first shear force exerted in a first shear direction perpendicular to the first direction in the first in-plane direction based on a change in a first capacitance produced between the first driving electrode and the first detection electrode and a change in a second capacitance produced between the second driving electrode and the first detection electrode, and
detect a second shear force exerted in a second shear direction perpendicular to the second direction in the first in-plane direction based on a change in a third capacitance produced between the third driving electrode and the second detection electrode and a change in a fourth capacitance produced between the fourth driving electrode and the second detection electrode.
12 . The detection unit according to claim 10 , further comprising a touch sensor overlapped on the first electrode layer in the first normal direction, wherein
the detection unit is configured to be capable of detecting a contact made by the touch sensor.
13 . The detection unit according to claim 10 , further comprising a first shield layer and a second shield layer, wherein
the first shield layer, the first insulating layer, the first electrode layer, the insulating elastic body layer, the second electrode layer, the second insulating layer, and the second shield layer are arranged in an order presented in the first normal direction,
the first shield layer and the second shield layer are made of sheet-like conductors respectively overlapped on whole surfaces of the first electrode layer and the second electrode layer when viewed in the first normal direction, and
the first insulating layer insulates the first electrode layer and the first shield layer, and the second insulating layer insulates the second electrode layer and the second shield layer.
14 . The detection unit according to claim 10 , further comprising a wiring part that connects the first detection electrode and the second detection electrode to the first electrode layer and the second electrode layer, wherein
the wiring part has a flexible portion that is easier to deform than a whole structure including the first electrode layer, the second electrode layer, and the insulating elastic body layer.
15 . The detection unit according to claim 10 , wherein
the first electrode layer, the second electrode layer, and the insulating elastic body layer are bent,
the insulating elastic body layer is elastically deformable also in a second in-plane direction different from the first in-plane direction,
a fifth driving electrode and a sixth driving electrode insulated from each other by a third isolation trench extending in the second in-plane direction and spreading in the second in-plane direction are formed in the first electrode layer,
the third isolation trench has a third portion extending in a third direction in the second in-plane direction,
a third detection electrode overlapped on the fifth driving electrode, the third portion of the third isolation trench, and the sixth driving electrode when viewed in a second normal direction perpendicular to the second in-plane direction is formed in the second electrode layer, and
the detection circuit detects a third shear force exerted in a third shear direction perpendicular to the third direction in the second in-plane direction based on a change in a fifth capacitance produced between the fifth driving electrode and the third detection electrode and a change in a sixth capacitance produced between the sixth driving electrode and the third detection electrode.
16 . The shear force sensor according to claim 1 , wherein the detection circuit detects the first and second shear force changes at the time when an AC voltage is applying to the first driving electrode and the second driving electrode, and wherein the AC voltage is applying to the first driving electrode and the second driving electrode at different timings.
17 . The shear force sensor according to claim 10 , wherein the detection circuit detects the first and second shear force changes at the time when an AC voltage is applying to the first driving electrode and the second driving electrode, and wherein the AC voltage is applying to the first driving electrode and the second driving electrode at different timings.
18 . The force sensor according to claim 1 , wherein the first electrode layer, the second electrode layer, and the insulating layer are alternately bonded to a curve surface so that a shear force along the curved surface can be measured.
19 . A method for measuring a shear force sensed by the shear force sensor of claim 1 , the method comprising:
applying an AC voltage to the first driving electrode and the second driving electrode at different timing;
measuring a change in a first capacitance produced between the first driving electrode and the first detection electrode and a change in a second capacitance produced between the second driving electrode and the first detection electrode;
calculating a first shear force exerted in a first shear direction perpendicular to the first direction in the first in-plane direction based on the measured change in the first capacitance and the second capacitance;
measuring a change in a third capacitance produced between the third driving electrode and the second detection electrode and a change in a fourth capacitance produced between the fourth driving electrode and the second detection electrode at the time the AC voltage is applied to the third and fourth driving electrode; and
calculating a second shear force exerted in a second shear direction perpendicular to the second direction in the first in-plane direction based on the measured change in the third capacitance and the fourth capacitance.
20 . The method according to claim 19 , further comprising
measuring a change in a fifth capacitance produced between a fifth driving electrode and a third detection electrode and a change in a sixth capacitance produced between a sixth driving electrode and a third detection electrode; and
calculating a third shear force exerted in a third shear direction perpendicular to a third direction in a second in-plane direction.