Sensor element, force detecting device, robot and sensor device

Abstract

A sensor element includes a piezoelectric substrate made of a trigonal single crystal and an electrode arranged on the piezoelectric substrate. The substrate surface of the piezoelectric substrate includes an electrical axis of crystal axes. An angle θ formed by the substrate surface and a plane including the electrical axis and an optical axis of the crystal axes is 0°<θ<20°.

What is claimed is: 
     
         1 . A robot comprising:
 a piezoelectric substrate including a trigonal single crystal having crystal axes;   a first electrode on a first surface of the piezoelectric substrate;   a second electrode on a second surface, the first and second surfaces being on opposite sides of the piezoelectric substrate;   an arithmetic unit which detects an amount of electric charge induced in the first or second electrode and calculates a force applied to the piezoelectric substrate;   a rotatable arm portion; and   a hand portion supported on the arm portion via the piezoelectric substrate, the hand portion being adapted to grip an object;   wherein the first surface of the piezoelectric substrate includes an electrical axis of the crystal axes,   an angle θ between the first surface and a plane including the electrical axis and an optical axis of the crystal axes is 0°<θ<20°, and   a material for the piezoelectric electric substrate is selected from the group consisting of langasite (La 3 Ga 5 SiO 14 ), lithium niobate (LiNbO 3 ) single crystal, lithium tantalite (LiTaO 3 ) single crystal, gallium phosphate (GaPO 4 ) single crystal, and lithium borate (Li 2 B 4 O 7 ) single crystal.   
     
     
         2 . The robot according to  claim 1 , comprising four of the sensor units. 
     
     
         3 . The robot according to  claim 1 , wherein the first surface of the piezoelectric substrate includes the electrical axis, a mechanical axis, and an optical axis of the crystal axes,
 a portion of an outer side surface that is different from the first and second surfaces of the piezoelectric substrate includes a plane, and   an angle λ between the plane of the outer side surface and a plane including an electrical axis and the optical axis of the crystal axes is 25°≦λ≦85°.   
     
     
         4 . A robot comprising:
 a piezoelectric substrate including a trigonal single crystal having crystal axes;   a first electrode on a first surface of the piezoelectric substrate; and a second electrode on a second surface, the first and second surfaces being on opposite sides of the piezoelectric substrate;   an arithmetic unit which detects an amount of electric charge induced in the first electrode or the second electrode and calculates a force applied to the piezoelectric substrate;   a rotatable arm portion; and   a hand portion supported on the arm portion via the sensor element, the hand portion being adapted to grip an object;   wherein the first surface of the piezoelectric substrate includes a mechanical axis and an optical axis of the crystal axes,   an outer side surface being different from the first and second surfaces of the piezoelectric substrate includes a plane,   an angle λ between the plane of the outer surface and a plane including an electrical axis and the optical axis of the crystal axes is 25°≦λ≦85°, and   a material for the piezoelectric electric substrate is selected from the group consisting of langasite (La 3 Ga 5 SiO 14 ), lithium niobate (LiNbO 3 ) single crystal, lithium tantalite (LiTaO 3 ) single crystal, gallium phosphate (GaPO 4 ) single crystal, and lithium borate (Li 2 B 4 O 7 ) single crystal.   
     
     
         5 . The robot according to  claim 4 , comprising four of the sensor units.