Stress detection method for force sensor device with multiple axis sensor and force sensor device employing this method

A stress detection method for a force sensor device with a multiple axis sensor comprising, as the multiple axis sensor:

• first and second force sensors the directions of which form an angle Φ in mutually opposite directions with the direction of a detected stress F1;
• and
• a third force sensor with a detection axis in a direction that is perpendicular to the plane formed with the detection axes of the first and second force sensors,
• wherein, when the plane formed with the detection axes of the first and second force sensors forms an angle θ with the axis direction of the detected stress F1, and the stress component in an axis direction that is perpendicular to the axis in which the detected stress F1 is delivered is F2,
• an output Fx of the axis direction of the first force sensor is found as Fx=αx×(F1×cos Φ×cos θ−F2×sin θ),
• an output Fy of an axis direction of the second force sensor is found as Fy=αy×(F1×cos Φ×cos θ−F2×sin θ),
• an output Fz of an axis direction of the third force sensor is found as Fz=αz×(F1×sin θ−F2×cos θ), and
• the combined output F of the outputs Fx, Fy and Fz is found as F=Fx+Fy−Fz;
• and,
• when αx, αy and αz are detection sensitivity coefficients of the first, second, and third force sensors respectively, the detection sensitivity coefficient αz of the third force sensor is αz=(αx+αy)×tan θ, and the detected stress F1 is then found from the composite output F as F1=F/{(αx+αy)cos Φ×cos θ−αz×sin θ}.

A force sensor device with a multiple axis sensor comprising:

• first and second force sensors the detection axes of which are mutually orthogonal;
• and
• a circuit for processing the outputs of the first and second force sensors,
• wherein, when the detection axis of the first force sensor forms an angle θ with the axis direction in which the detected stress Ax is delivered and the stress component of an axis direction that is perpendicular to the axis in which the detected stress Ax is delivered is Az, the circuit outputs:
• Apx=αx (Ax×cos θ+Az×sin θ) as an output in the axis direction of the first force sensor, and
• Apz=αz (Ax×sin θ+Az×cos θ) as an output in the axis direction of the second force sensor,
• where αx and αz are detection sensitivity coefficients of the first and second force sensors respectively and the detection sensitivity coefficient αz of the second force sensor is set as αz=αx tan θ;
• the difference Apx−Apz between the output Apx and output Apz is found;
• and
• the detected stress Ax is detected from the difference and outputted as Ax=(Apx−Apz)/αx(cos θ−tan θ×sin θ).

A force sensor device with a multiple axis sensor comprising, as the multiple axis sensor:

• first and second force sensors that form an angle Φ in mutually opposite directions with the axis direction in which the detected stress F1 is delivered;
• and
• a third force sensor with a detection axis in a direction that is perpendicular to the plane formed with the detection axes of the first and second force sensors, the plane formed with the first and second force sensors forming an angle θ with the axis direction in which the detected stress F1 is delivered;
• and
• a circuit that processes the outputs of the first, second, and third force sensors, such that, when the stress component in an axis direction that is perpendicular to the axis in which the detected stress F1 is delivered is F2, the circuit outputs:
• an output Fx of the axis direction of the first force sensor as Fx=αx×(F1×cos Φ×cos θ−F2×sin θ),
• an output Fy of the axis direction of the second force sensor as Fy=αy×(F1×cos Φ×cos θ−F2×sin θ),
• an output Fz of the axis direction of the second force sensor as Fz=αz×(F1×sin θ−F2×cos θ), and
• the combined output F of the outputs Fx, Fy and Fz as F=Fx+Fy−Fz;
• and,
• wherein αx, αy and αz are detection sensitivity coefficients of the first, second, and third force sensors respectively,
• the detection sensitivity coefficient αz of the third force sensor is αz=(αx+αy)×tan θ, and
• the detected stress F1 is obtained from the composite output F and outputted as F1=F/{(αx+αy)cos Φ×cos θ−αz×sin θ}.

A force sensor device that detects stress delivered in a detected axis direction comprising:

• a frame portion with outside edges of a rectangular shape;
• a weight that is disposed within the frame portion;
• and
• four flexible beams that are arranged in orthogonal axis directions that pass through the center of the weight, the respective one end of which is connected to the weight and the respective other end of which is connected to the frame portion at an inclination that forms a 45° angle with the outside edge of the frame portion,
• wherein each of the four flexible beams comprises a detection element a physical quantity of which varies according to the flexibility of the beams when stress is delivered to the weight.

A force sensor device that detects stress delivered in a detected axis direction, comprising:

• a frame portion with outside edges of a rectangular shape;
• a weight that is disposed within the frame portion;
• four flexible beams that are arranged in orthogonal axis directions that pass through the center of the weight, the respective one end of which is connected to the weight and the respective other end of which is connected to the frame portion at an inclination that forms a 45° angle with the outside edge of the frame portion;
• a first electrode portion that is formed on the weight and on each of the four flexible beams;
• and
• an opposing electrode portion that is disposed to face the first electrode portion via an insulator,
• wherein the capacitance between the first electrode portion and the opposing electrode portion varies according to the flexibility of the beams when stress is delivered to the weight.