Disclosure of Invention
The invention aims to overcome the technical defects and provide a Z-axis accelerometer which is used for solving the problem of measurement errors caused by substrate warpage or unbalanced anchor points in the prior art.
In order to achieve the technical purpose, the technical scheme of the invention is as follows: a Z-axis accelerometer, comprising: a substrate, a first mass, a second mass, and at least one anchor secured to a surface of the substrate, wherein: the first mass block and the second mass block are respectively and elastically connected with the at least one anchor, are suspended on the substrate, and are configured to perform resonance movement along the direction perpendicular to the substrate around a dividing line, wherein the dividing line is a straight line where the at least one anchor is positioned, and divides the plane where the substrate is positioned into a first area and a second area; the first mass block comprises a first mass part and a second mass part, wherein the first mass part is positioned in the first area and the second mass part is positioned in the second area and is divided by the dividing line, and the movement directions of the first mass part and the second mass part are opposite; the second mass block comprises a third mass part and a fourth mass part, wherein the third mass part and the fourth mass part are divided by the dividing line and are positioned in the first area, and the movement directions of the third mass part and the fourth mass part are opposite to each other and are opposite to the movement direction of the first mass part; pairs of electrodes are provided between the first and second masses and the substrate to form a plurality of capacitances between the first and second masses and the substrate.
Preferably, the first mass is m 1, the second mass is m 2, and m 1 >2, the third mass is m 3, the fourth mass is m 4, and m 3 <4.
Preferably, capacitive structures are respectively arranged between the first mass part, the second mass part, the third mass part and the fourth mass part and the substrate.
Preferably, each capacitor structure comprises two capacitors, each capacitor comprises a bottom electrode arranged on the substrate and a top electrode arranged on the corresponding mass part, and the top electrode is opposite to the bottom electrode.
Preferably, each of said capacitor structures comprises two of said capacitors symmetrically arranged about a first central axis, said first central axis being perpendicular to said dividing line.
Preferably, the two capacitance structures corresponding to the first mass portion and the second mass portion are symmetrically arranged about the dividing line, and the two capacitance structures corresponding to the third mass portion and the fourth mass portion are symmetrically arranged about the dividing line.
Preferably, the distances between each pair of electrodes and the dividing line are equal.
Preferably, the first mass block is provided with an embedded hole, and the second mass block is arranged in the embedded hole.
Preferably, the first mass portion has a proximal end near the dividing line and a distal end remote from the dividing line, the second mass portion has a proximal end near the dividing line and a distal end remote from the dividing line, the third mass portion has a proximal end near the dividing line and a distal end remote from the dividing line, the fourth mass portion has a proximal end near the dividing line and a distal end remote from the dividing line, and the electrodes are disposed at the distal end of the first mass portion, the distal end of the second mass portion, the distal end of the third mass portion, and the distal end of the fourth mass portion, respectively.
Preferably, the facing areas of the plurality of pairs of the electrodes are the same.
Compared with the prior art, the invention has the beneficial effects that: when the acceleration of the Z-axis accelerometer changes, the heavy side deflects in the acceleration direction due to the asymmetrically distributed mass on the two sides, and the light side deflects in the opposite direction of the acceleration direction. Moreover, the greater the acceleration is, the greater the deflection degree is, because the heavy sides of the first mass block and the heavy sides of the second mass block are respectively distributed in the first area and the second area, and the deflection directions of the first mass block and the second mass block are opposite, when one side of the accelerometer is warped, the capacitance of the corresponding positions of the first mass block and the second mass block generates capacitance variation with the same size, and because the Z-axis accelerometer adopts differential calculation, the capacitance variation corresponding to the first mass block and the second mass block is counteracted, and therefore, the error generated by warping can be effectively avoided. In addition, when the anchors are unbalanced, the first mass block and the second mass block deflect, and the deflection has the same effect on the two mass blocks, capacitance changes are generated at two ends of the first mass block and the second mass block, and the capacitance changes can be counteracted in differential calculation, so that errors caused by the anchors are avoided.
Detailed Description
Referring to fig. 1, a schematic structural diagram of a typical accelerometer in the prior art is shown. The device is of a single seesaw structure, a flat plate is arranged on a substrate, is connected with the substrate through an anchor and can do seesaw motion around the anchor, the left side and the right side of the flat plate are provided with mass blocks with different masses, and electrodes are respectively arranged on the left side and the right side of the flat plate and respectively form a capacitor with the electrodes of the substrate.
The accelerometer is only affected by gravity acceleration, so that the flat plate reaches an equilibrium state, and the distance between the left and right sides of the flat plate and the substrate is kept unchanged, namely the zero point of the accelerometer.
When the acceleration of the flat plate is changed, the left and right masses of the flat plate are different, so that the stress is also different, the flat plate deflects, moves in the opposite directions, the distance between the two opposite electrodes is changed, the corresponding capacitance value is also changed, and the larger the acceleration of the flat plate is changed, the larger the difference value between the left and right capacitances is, so that the acceleration of the external force exerted on the flat plate can be represented by the difference value between the left and right capacitances.
However, the inventors have found that when the substrate deflects the plate due to deformation or anchor imbalance on one side due to stress, temperature, etc., the plate-to-substrate spacing changes, thereby changing the capacitance value, and the corresponding accelerometer zero point changes, which would otherwise result in inaccurate measurement results.
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Referring to fig. 2 and 3, fig. 2 is a top view of a Z-axis accelerometer according to the present invention, and fig. 3 is a front view of the Z-axis accelerometer in a balanced state according to the present invention. The present invention provides a Z-axis accelerometer, comprising: a substrate 1, a first mass 2, a second mass 3, anchors 4 and springs 5, wherein: the first mass 2 and the second mass 3 are connected to the substrate 1 by means of anchors 4, respectively, and are configured to each move like a see-saw around a dividing line parallel to the substrate 1, which dividing line divides the plane into a first area and a second area, the first mass 2 and the second mass 3 being elastically connected to the anchors 4, respectively, in the preferred embodiment the first mass 2 and the second mass 3 being connected to the anchors 4 by springs 5, respectively.
The first mass 2 comprises a first mass portion 21 located in a first region and a second mass portion 22 located in a second region, which are divided by a dividing line, the directions of movement of the first mass portion 21 and the second mass portion 22 being opposite. The second mass 3 comprises a third mass portion 31 located in the first region and a fourth mass portion 32 located in the second region, which are divided by a dividing line, the direction of movement of the third mass portion 31 and the fourth mass portion 32 being opposite to the direction of movement of the first mass portion 21.
Specifically, the left and right sides of the first mass 2 and the second mass 3 may be configured to have different masses, so that the Z-axis accelerometer may deflect when the Z-axis accelerometer is subject to an acceleration change, the first mass 2 is divided into a first mass portion 21 with a mass of m 1 and a second mass portion 22 with a mass of m 2 in a first region by a dividing line, and m 1>m2, the second mass 3 is divided into a third mass portion 31 with a mass of m 3 and a fourth mass portion 32 with a mass of m 4 in a second region by a dividing line, and m 3<m4. The both ends of the first mass portion 21 and the second mass portion 22 are not equal in mass, and the relatively heavy end of the first mass portion 21 and the relatively heavy end of the second mass portion 22 are located on both sides of the dividing line, respectively.
The first mass block 2 and the second mass block 3 are respectively provided with paired electrodes near the substrate 1 so as to form a plurality of capacitors between the first mass block 2 and the substrate 1 and between the second mass block 3 and the substrate 1, wherein the rotation angles of the two sides are the same when the first mass block 2 and the second mass block 3 rotate, if the distances from the electrodes to the dividing line are different, the change distances of the electrodes are also different, the capacitance change amounts are different, the correction is not performed, and the acceleration cannot be accurately calculated, so that the distances from the electrodes to the dividing line are required to be ensured to be the same, the change amounts of the left and right capacitors are required to be ensured to be the same, and the ratio of the capacitance value of the electrodes to the spacing between the corresponding electrodes is the correction value if the distances from the electrodes to the dividing line are different. The first, second, third and fourth masses 21, 22, 31, 32 form first, second, third and fourth capacitances C 1, C 2, C 3, C 4, respectively, with the substrate 1.
As a preferred embodiment, Δz=c 1+C3-C2-C4 is used to characterize the Z-axis acceleration magnitude and direction of the accelerometer. Specifically, for the single-see-saw structure, Δz=c 1-C2, where C 1 and C 2 are the capacitances on both sides of the mass respectively, and when one side is warped, Δz=c 1+ΔC-C2, where Δc is the capacitance change due to deformation of the mass due to stress or other factors, and therefore, the single-see-saw structure cannot avoid errors due to warpage.
Referring to fig. 4 and 5 for a double teeter-totter structure, fig. 4 is a front view of a Z-axis accelerometer according to the present invention when the acceleration changes and deflects, and fig. 5 is a front view of the Z-axis accelerometer according to the present invention when one side of the acceleration warps. Δz=c 1+C4-C2-C3, when one side of the mass is warped due to stress, the mass portions of the two masses located on the same side deform to the same extent, for example: the first mass portion and the third mass portion deform to the same extent, so that the first capacitance and the third capacitance on the same side generate the same variation Δc, and at this time Δz=c 1+ΔC+C4-(C3+ΔC)-C2=C1+D4-C2-C3, that is, the capacitance variation is cancelled out.
When the two sides are warped, the corresponding first mass part and the corresponding third mass part deform to the same extent, so that the first capacitor and the third capacitor on the same side generate the same variation delta C 1, and the second mass part and the fourth mass part deform to the same extent, so that the second capacitor and the fourth capacitor on the same side generate the same variation delta C 2, and at the moment ΔZ=C1+ΔC1+(C4+ΔC2)-(C3+ΔC1)-(C2+ΔC2)=C1+C4-C2-C3,, namely the capacitance variation is counteracted.
Therefore, the double-see-saw structure in this embodiment can effectively avoid the error generated by the warpage, and the warpage can be offset at any one side or both sides, and it needs to be further explained that, when the anchor 4 changes to cause the first mass block 2 and the second mass block 3 to generate the same deflection, the situation is similar to the situation that the warpage occurs at the two sides, and the error can still be offset, which is not repeated here.
As a preferred embodiment, the first capacitor comprises two pairs of electrodes, a first electrode 61 having a capacitance of C 11 and a second electrode 62 having a capacitance of C 12, and C 1=C11+C12, and the second capacitor comprises two pairs of electrodes, a third electrode 63 having a capacitance of C 21 and a fourth electrode 64 having a capacitance of C 22, and C 2=C21+C22. Further preferably, the Z-axis accelerometer has a first central axis, the first electrode 61 and the second electrode 62 are axisymmetric with respect to the first central axis, the third electrode 63 and the fourth electrode 64 are axisymmetric with respect to the first central axis, and the distances from the first electrode 61 and the third electrode 63 to the first central axis are equal, so that the first electrode 61, the second electrode 62, the third electrode 63 and the fourth electrode 64 are just in four corners of a rectangle, and the two central axes of the rectangle are the first central axis and the dividing line, respectively.
Similarly, as a preferred embodiment, the third capacitor includes two pairs of electrodes, a fifth electrode 65 having a capacitance of C 31 and a sixth electrode 66 having a capacitance of C 32, and C 3=C31+C32, and the fourth capacitor includes two pairs of electrodes, a seventh electrode 67 having a capacitance of C 41 and an eighth electrode 68 having a capacitance of C 42, and C 4=C41+C42. Further preferably, the Z-axis accelerometer has a second central axis, the fifth electrode 65 and the sixth electrode 66 are axisymmetric with respect to the second central axis, the seventh electrode 67 and the eighth electrode 68 are axisymmetric with respect to the second central axis, and the distances from the fifth electrode 65 and the seventh electrode 67 to the second central axis are equal, so that the fifth electrode 65, the sixth electrode 66, the seventh electrode 67 and the eighth electrode 68 are just positioned at four corners of a rectangle, and the two central axes of the rectangle are respectively the second central axis and a dividing line, and the stability of the second mass block 3 can be ensured by adopting the symmetrical arrangement mode.
It should be noted that each capacitor includes two electrodes, one electrode is disposed on the substrate, the other electrode is disposed on the corresponding mass, and the pair of electrodes are disposed opposite to each other or partially disposed opposite to each other. If the facing areas of the electrodes of different pairs are different, when the electrode spacing of the two pairs of electrodes positioned on two sides of the same mass block is changed identically, the capacitance value is changed differently, so that the capacitance value also needs to be corrected, and at this time, the ratio of the capacitance value to the facing area of the corresponding electrode can be adopted as a correction value.
In a preferred embodiment, the opposite areas of the plurality of pairs of electrodes are the same, and the opposite areas of the electrodes are the same, so that the change amount of the corresponding capacitance is the same under the same displacement, and therefore, compensation and correction on the measured capacitance value are not needed.
It is further preferred that the first central axis is coaxial with the second central axis, i.e. the symmetry axis of the first electrode 61 and the third electrode 63, so that the electrodes on the first mass 2 and the second mass 3 are symmetrically arranged, ensuring the stability of the whole accelerometer.
As a preferred embodiment, the first mass block 2 is provided with a hole, and the second mass block 3 is arranged in the hole, so that the first mass block 2 and the second mass block 3 can be prevented from being interfered by movement. The structure is nested mutually, and the external mass block is a closed ring, so that the upper side and the lower side can synchronously move, and the instability of the structure is reduced.
As a preferred embodiment, the first mass portion 21 has a proximal end near the dividing line and a distal end far from the dividing line, the second mass portion 22 has a proximal end near the dividing line and a distal end far from the dividing line, the third mass portion 31 has a proximal end near the dividing line and a distal end far from the dividing line, the fourth mass portion 32 has a proximal end near the dividing line and a distal end far from the dividing line, and electrodes are respectively provided at the distal ends of the first mass portion 21, the second mass portion 22, the third mass portion 31 and the fourth mass portion 32, and the displacement of the distal ends is larger than that of the proximal ends when the first mass portion 2 and the second mass portion 3 are rotated, so that the arrangement of the electrodes at the distal ends can increase the capacitance variation and improve the sensitivity.
In summary, the present invention provides a Z-axis accelerometer, which adopts a double-seesaw structure, and when the acceleration of the Z-axis accelerometer changes, the heavy side deflects in the acceleration direction and the light side deflects in the opposite direction due to the asymmetric distribution of the two sides. Moreover, the greater the acceleration, the greater the deflection degree, because the heavy side of the first mass block 2 and the heavy side of the second mass block 3 are respectively distributed in the first area and the second area, the deflection directions of the first mass block 2 and the second mass block 3 are opposite, when one side of the Z-axis accelerometer is warped, the capacitance variation of the corresponding positions of the first mass block 2 and the second mass block 3 generates the same capacitance variation, and the Z-axis accelerometer adopts differential calculation, so that the capacitance variation of the corresponding positions of the first mass block 2 and the second mass block 3 is counteracted, and the error generated by the warping can be effectively avoided. In addition, when the anchors 4 are unbalanced and deflect the first mass 2 and the second mass 3, the deflection has the same effect on both masses, and capacitance changes are generated at both ends of the first mass 2 and the second mass 3, and similarly, the capacitance changes can be offset in differential calculation.
Although the application has been shown and described with respect to one or more implementations, equivalent alterations and modifications will occur to others skilled in the art based upon a reading and understanding of this specification and the annexed drawings. The present application includes all such modifications and alterations and is limited only by the scope of the following claims. In particular regard to the various functions performed by the above described components, the terms used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the component (e.g., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary implementations of the specification.
That is, the foregoing embodiments of the present application are not limited to the patent scope of the application, and all equivalent structures or equivalent processes using the descriptions and the drawings of the present application, such as combining technical features of the embodiments, or directly or indirectly using other related technical fields, are included in the scope of the present application.
In addition, in the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present application. In addition, the present application may be identified by the same or different reference numerals for structural elements having the same or similar characteristics. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more features. In the description of the present application, the meaning of "a plurality" is two or more, unless explicitly defined otherwise. In the present application, the term "exemplary" is used to mean "serving as an example, instance, or illustration. Any embodiment described as "exemplary" in this disclosure is not necessarily to be construed as preferred or advantageous over other embodiments. The previous description is provided to enable any person skilled in the art to make or use the present application. In the above description, various details are set forth for purposes of explanation. It will be apparent to one of ordinary skill in the art that the present application may be practiced without these specific details. In other instances, well-known structures and processes have not been shown in detail to avoid unnecessarily obscuring the description of the application. Thus, the present application is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.