Force sensor

A force sensor comprising:

• a circuit board arranged at a position where an upper surface thereof is contained in an X-Y plane when an XYZ three-dimensional coordinate system is defined;
• an acting body attached to the upper surface of said circuit board, said acting body having a displacement portion arranged above said circuit board and displaced when an external force is applied thereto, a securing portion fixed to said circuit board, and a connecting portion for connecting said displacement portion to said securing portion;
• an elastic deformation body, formed on a lower, surface of said displacement portion and having elastic deformation properties;
• a switch displacement electrode formed on a lower surface of said elastic deformation body;
• a switch securing electrode formed on a position opposite to said switch displacement electrode on said circuit board;
• and
• a capacitor adapted to produce a variation in capacitance caused by a displacement of said displacement portion;
• wherein said connecting portion has flexibility so that when a force is applied to said displacement portion, a deflection is produced in said connecting portion, thereby causing a displacement in said displacement portion relative to said circuit board;
• wherein when no force is applied to said displacement portion, said switch displacement electrode and said switch securing electrode are not kept in contact with each other, and when a force of a predetermined amount, including a component along a Z-axis of said coordinate system, is applied to said displacement portion, said switch displacement electrode and said switch securing electrode are brought into control with each other;
• wherein when a further force, including a component along said taxis, is applied to said displacement portion, said elastic deformation body is elastically deformed, thereby allowing capacitance of amid capacitor to vary, with the contact state kept unchanged between said switch displacement electrode and said switch securing electrode;
• and
• wherein said switch displacement electrode and said switch securing electrode form a switch which is closed when said displacement electrode is brought into contact with said securing electrode, whereafter when said elastically deformable body is elastically deformed, a change in capacitance of said capacitor is electrically detected to thereby recognize magnitude of a predetermined directional component of an applied force.