Acceleration sensor
View Patent ↗The piezo-resistance type triaxial acceleration sensor includes a frame section, a mass section disposed in the frame section, beam elements which flexibly support the mass section, and piezo-resistors for X, Y and Z axes of the frame section, formed on the beam elements. The length of the Z-axis piezo-resistors is longer than the length of the X-axis piezo-resistors and the Y-axis piezo-resistors, so as to decrease the sensitivity.
1. An acceleration sensor, comprising:
a frame section definable relative to a three dimensional coordinate system with having X, Y and Z orthogonal axes such that the X axis and Y axis define a plane in which the frame section generally extends;
a mass section disposed inside the frame section;
a plurality of X-direction beam elements extending in an X axis direction for flexibly connecting the mass section to the frame section;
a plurality of X-axis acceleration sensor elements provided in the plurality of X-direction beam elements, respectively, for detecting acceleration of the mass section in the X-axis direction, each said X-axis acceleration sensor element having a first length; and
a plurality of Z-axis acceleration sensor elements provided in the plurality of X-direction beam elements, respectively, for detecting acceleration of the mass section in the Z-axis direction, each said Z-axis acceleration sensor element having a second length, the second length being greater than the first length,
wherein each said X-axis acceleration sensor element extends in areas of largest distortion of the associated X-direction beam element, and
wherein at least one of the Z-axis acceleration sensor elements extends onto the frame section.
2. The acceleration sensor according to claim 1 , wherein the plurality of X-direction beam elements are two X-direction beam elements which are connected to opposite faces of the mass section.
3. The acceleration sensor according to claim 1 , further comprising a plurality of Y-direction beam elements extending in a Y-axis direction, such that the plurality of Y-direction beam elements also flexibly connect the mass section to the frame section.
4. The acceleration sensor according to claim 3 , further comprising a plurality of Y-axis acceleration sensor elements provided in the plurality of Y-direction beam elements, respectively, for detecting acceleration of the mass section in the Y-axis direction, each said Y-axis acceleration sensor element having the first length.
5. The acceleration sensor according to claim 1 , wherein the first length is about 50 μm and the second length is about 60-70 μm.
6. The acceleration sensor according to claim 1 , wherein each said X-axis acceleration sensor element is a pair of piezo-resistors.
7. An acceleration sensor, comprising:
a frame section definable relative to a three dimensional coordinate system with having X, Y and Z orthogonal axes such that the X axis and Y axis define a plane in which the frame section generally extends;
a mass section disposed inside the frame section;
a plurality of X-direction beam elements extending in an X axis direction for flexibly connecting the mass section to the frame section;
a plurality of X-axis acceleration sensor elements provided in the plurality of X-direction beam elements, respectively, for detecting acceleration of the mass section in the X-axis direction, each said X-axis acceleration sensor element having a first length; and
a plurality of Z-axis acceleration sensor elements provided in the plurality of X-direction beam elements, respectively, for detecting acceleration of the mass section in the Z-axis direction, each said Z-axis acceleration sensor element having a second length, the second length being greater than the first length,
wherein each said X-axis acceleration sensor element extends in areas of largest distortion of the associated X-direction beam element, and
wherein each Z-axis acceleration sensor element is disposed parallel to an adjacent X-axis acceleration sensor element to form an acceleration sensor element pair, the Z-axis acceleration sensor element of each pair having ends that are not aligned with the ends of the X-axis acceleration sensor element of the respective pair, so that the X-axis and Z-axis acceleration sensor elements of the respective pair are offset from one another.