Acceleration sensor

Abstract

An acceleration sensor includes a piezoelectric single-plate having a weight part and a detection part. The piezoelectric single-plate is, for example, an X-cut plate of LiNbO 3 .

What is claimed is:  
     
         1 . An acceleration sensor comprising: 
 a piezoelectric single-plate having a weight part and a detection part.    
     
     
         2 . The acceleration sensor as claimed in    claim 1   , further comprising: 
 a detection electrode provided on a first surface of the piezoelectric single-plate, an electric signal caused by inertia force exerted onto the weight part resulting from acceleration being output via the detection electrode; and    a ground electrode provided on a second surface of the piezoelectric single-plate opposite to the first surface.    
     
     
         3 . The acceleration sensor as claimed in    claim 2   , wherein the detection electrode comprises two electrode parts arranged side by side in a direction in which the acceleration is applied to the acceleration sensor.  
     
     
         4 . The acceleration sensor as claimed in    claim 2   , wherein the detection electrode comprises two electrode parts arranged side by side in a direction perpendicular to another direction in which the acceleration is applied to the acceleration sensor.  
     
     
         5 . The acceleration sensor as claimed in    claim 1   , wherein the piezoelectric single-plate has a supporting position which does not include a center of gravity of the piezoelectric single-plate.  
     
     
         6 . The acceleration sensor as claimed in    claim 1   , wherein the piezoelectric single-plate has a supporting position which includes a center of gravity of the piezoelectric single-plate.  
     
     
         7 . The acceleration sensor as claimed in    claim 1   , wherein the piezoelectric single-plate has a supporting position with which the detection electrode overlaps.  
     
     
         8 . The acceleration sensor as claimed in    claim 1   , wherein the piezoelectric single-plate is an X-cut plate of LiNbO 3 .  
     
     
         9 . The acceleration sensor as claimed in    claim 2   , further comprising another ground electrode provided on the first surface of the piezoelectric single-plate.  
     
     
         10 . The acceleration sensor as claimed in    claim 2   , wherein the ground electrode is thicker than the detection electrode.  
     
     
         11 . The acceleration sensor as claimed in    claim 2   , wherein the detection electrode and the ground electrodes have respective densities that are greater than a density of the piezoelectric single-plate.  
     
     
         12 . The acceleration sensor as claimed in    claim 9   , further comprising an electrically conductive resin that electrically connects the ground electrode and said another ground electrode.  
     
     
         13 . The acceleration sensor as claimed in    claim 9   , further comprising an insulating resin provided in a groove that separates the detection electrode and said another ground electrode from each other.  
     
     
         14 . The acceleration sensor as claimed in    claim 2   , further comprising: 
 a package to which the piezoelectric single-plate is attached;    an electrode terminal provided on the package; and    an electrically conductive adhesive agent which attaches the piezoelectric single-plate to the package and electrically connects the detection electrode and the electrode terminal.    
     
     
         15 . The acceleration sensor as claimed in    claim 2   , further comprising: 
 a package to which the piezoelectric single-plate is attached;    an electrode terminal provided on the package; and    an anisotropic electrically conductive adhesive agent which attaches the piezoelectric single-plate to the package and electrically connects the detection electrode and the electrode terminal.    
     
     
         16 . The acceleration sensor as claimed in    claim 2   , further comprising a flexible printed-circuit cable to which the detection electrode and the ground electrode are connected.  
     
     
         17 . The acceleration sensor as claimed in    claim 2   , further comprising wires connecting the detection electrode and the ground electrodes to electrode terminals formed on a member by which the piezoelectric single-plate is supported.  
     
     
         18 . The acceleration sensor as claimed in    claim 2   , further comprising: 
 a package which accommodates the piezoelectric single-plate; and    an electrically conductive resin which electrically connects the ground electrode to an electrode terminal provided on the package.    
     
     
         19 . The acceleration sensor as claimed in    claim 1   , further comprising: 
 an electric circuit that processes an electric signal output from the piezoelectric single-plate; and    a package which accommodates the electric circuit and the piezoelectric single-plate.    
     
     
         20 . The acceleration sensor as claimed in    claim 19   , wherein the package is provided with a guide base positioning and supporting the piezoelectric single-plate.  
     
     
         21 . The acceleration sensor as claimed in    claim 19   , wherein the electric circuit is located below the piezoelectric single-plate.