CN201837400U - High-sensitivity capacitance sensor - Google Patents

Abstract

The utility model relates to a high-sensitivity capacitance sensor comprising a flexible beam, a fixed fork finger and a movable fork finger which is connected with the flexible beam and matched with the fixed fork finger. The fixed fork finger and the movable fork finger respectively comprise a bottom part and more than two bulge parts which are vertically connected with the bottom part. With the high-sensitivity capacitance sensor, the measuring sensitivity of devices is greatly improved by greatly increasing the equivalent change area of a capacitance polar plate.

Description

A kind of highly sensitive capacitive transducer

Technical field

The utility model relates to the capacitive transducer in a kind of micro electronmechanical (MEMS) field, relates in particular to a kind of highly sensitive capacitive transducer.

Background technology

Capacitance type sensor is that tested non electrical quantity is changed, and as displacement, pressure variation etc., is converted to a kind of sensor of electric capacitance change.But simple in structure, high resolution non-cpntact measurement, and can under mal-conditions such as high temperature, radiation and judder, work, this is its distinct advantages.Along with integrated circuit technique and development of computer, impel it to maximize favourable factors and minimize unfavourable ones, become the considerable sensor of a kind of prospect.

The responsive part of capacitance type sensor is exactly the capacitor with variable element.Its most frequently used form by two parallel poles form, interpolar with the air is the capacitor (see figure 1) of medium.If ignore edge effect, the account form of the inductance capacitance of plate condenser is:

$C=\frac{\mathrm{\ϵ}\·A}{g}---\left(1\right)$

ε is the specific inductive capacity of contrasted between solid dielectric in the formula 1, and A is the useful area that two electrodes cover mutually, and g is two distance between electrodes.The variation of any all will cause electric capacitance change in g, A, three parameters of ε, and can be used for measuring.Therefore capacitance type sensor can be divided into change spacing type, changed area and change medium type three classes.

Wherein, the inductance capacitance variable of change spacing type and changed area capacitance type sensor (seeing Fig. 2 A and Fig. 2 B) is respectively:

$\left|\mathrm{\&Delta;C}\right|=\frac{\mathrm{\&epsiv;<figure-callout\; id="2"\; label="A\; g"\; filenames="DEST\_PATH\_HSB00000434033800021.png"\; state="\{\{state\}\}">A</figure-callout>}}{g^{}}\left|\mathrm{\&Delta;g}\right|---\left(2\right)$

$\left|\mathrm{\&Delta;C}\right|=\frac{\mathrm{\&epsiv;}}{g}\left|\mathrm{\&Delta;A}\right|---\left(3\right)$

Find out that thus become in the structural design of spacing type electric capacity, capacitance variations becomes nonlinear relationship (seeing formula 2) with displacement, must in little displacement range, work so that linearization, but owing to the quadratic power factor of variable in the inductive relationship formula, the capacitance variations of acquisition is still higher.The resistance of motion that becomes pitch structure is generally the damping of air pressing mold.

In the changed area capacitance structure, capacitance variations and displacement are desirable linear relationship (seeing formula 3), can directly be directly proportional with acceleration in the spring range of linearity.Damping effect mainly is the synovial membrane air damping, and the resistance of generation helps obtaining higher resolution much smaller than press mold.But it is little to obtain relative capacitance variations in the traditional design, has limited the lifting of sensitivity.

The utility model content

Technical problem to be solved in the utility model is to overcome the existing little defective of capacitor sensor with changed area sensitivity, and a kind of highly sensitive capacitive transducer is provided.

In order to solve the problems of the technologies described above, the technical scheme that the utility model proposed is:

A kind of highly sensitive capacitive transducer, it comprise flexible beam, fixing interdigital and is connected with flexible beam and with the fixation fork assignment close movably interdigital, wherein fix interdigital and movably interdigital all comprise respectively bottom and the plural lug boss that is connected with described bottom vertical.

Further, in different embodiments, it is identical wherein to fix interdigital and movable interdigital structure.

Further, in different embodiments, the shape of wherein fixing interdigital or movable each lug boss on interdigital is identical.

Further, in different embodiments, wherein the xsect of lug boss is square.

Further, in different embodiments, wherein lug boss is big or small identical.

Further, in different embodiments, the interval width of wherein per two lug bosses is identical.

Further, in different embodiments, wherein fix interdigital and movable interdigital mutual dislocation and arrange, promptly fix interdigital lug boss and overlap with movable interdigital lug boss.

Further, in different embodiments, wherein fix and interdigitally comprise that first is fixing interdigital and second fixing interdigital, described first is fixing interdigital and second fix and interdigitally close the formation differential capacitance with the swinging fork assignment respectively.

Further, in different embodiments, wherein first is fixing interdigital and second fix and interdigitally have two groups respectively.

Compared with prior art, the beneficial effects of the utility model are: the highly sensitive capacitive transducer that the utility model relates to, with the fixing interdigital and movable interdigital structure that is processed into the similar broach that comprises bottom and the plural lug boss that is connected with bottom vertical, the equivalence that increases capacitor plate greatly changes area, thereby improves the sensitivity that device is measured greatly.

Description of drawings

Fig. 1 is a capacity plate antenna structural representation of the prior art;

Fig. 2 A is the structural representation that becomes spacing type capacitance type sensor in the prior art;

Fig. 2 B is the structural representation of changed area capacitance type sensor in the prior art;

Fig. 3 is the structural representation of a kind of embodiment of the highly sensitive capacitance type sensor that relates to of the utility model;

Fig. 4 is a pair of fixing interdigital and movable interdigital amplification stereogram among Fig. 3; With

Fig. 5 is the synoptic diagram of capacitor plate shown in Figure 4 when being subjected to displacement.

Embodiment

Describe embodiment of the present utility model in detail below in conjunction with accompanying drawing.

See also Fig. 3, a kind of highly sensitive capacitive transducer that the utility model relates to, it comprise flexible beam 1, fixing interdigital 3,4 and be connected with flexible beam 1 movable interdigital 5.Black part is divided into the fixed sturcture on the silicon chip among Fig. 3, and fixed sturcture comprises first fixing interdigital 3 and second fixing interdigital 4; The ash color part is the unsettled movable structure in bottom, and movable structure comprises flexible beam 1 and movable interdigital 5.In the present embodiment, first fixing interdigital 3 and second fixing interdigital 4 respectively has two groups, four groups of fixing interdigitally link together by anchor point 2, and corresponding to fixing interdigital 3,4, movable interdigital 5 also have four groups.First fixing interdigital 3 and second fixing interdigital 4 constitutes parallel plate capacitor C with movable interdigital 5 respectively ₁, C ₂, the two forms differential capacitance output.

Wherein fix interdigital 3,4 and movable interdigital 5 and be processed to the broach shape respectively, the equivalence that strengthens capacitor plate thus changes area.In the present embodiment, fixing interdigital 3,4 and movable interdigital 5 structure is identical, all comprises along axial bottom 61 of x and the lug boss 62 vertical with bottom 61, as shown in Figure 4.And in the present embodiment, the shape of the lug boss 62 that extends along the y axle all is identical, all be square, and the size of lug boss 62 is also identical, and particularly, the height of lug boss 62, width all are identical.In addition, the interval width of per two lug bosses 62 is also identical.What Fig. 3 bend was partly represented is exactly the sunk part of broach shape capacitor plate, compartment 63 promptly shown in Figure 4.Fixing interdigital 3,4 arrange with movable interdigital 5 mutual dislocation, promptly fix interdigital lug boss and overlap with movable interdigital lug boss.

Do the time spent when being subjected to the axial responsive external force of x, deformation takes place in flexible beam 1 on the x direction of principal axis, driving movable interdigital 5 moves, movable interdigital 5 with respect to fixing interdigital 3,4 are subjected to displacement Δ x on the x direction of principal axis, cause area between movable interdigital 5 and fixing interdigital 3, the 4 Δ A that changes, thereby make C ₁, C ₂Difference change, measure the responsive external force size that device is experienced thus, as shown in Figure 5.

ΔA＝n·h·Δx

Wherein, n is the lug boss number, and h is the lug boss height, and Δ x is the x direction displacement that responsive external force causes.

Be not difficult to find out from following formula, than traditional design, become the capacitive transducer of broach shape on the short transverse that the utility model relates to, because changing area, the capacitor plate equivalence increases n doubly, cause rate of change of capacitance to increase n doubly, the sensitivity of measuring under the same displacement situation can improve n doubly.

In different embodiments, fixing interdigital and movable interdigital structure can be different, and the shape of fixing each lug boss on interdigital or movable interdigital, size also can differences, and the interval width of per two lug bosses also can difference.First is fixing interdigital and second fix interdigital group number and the movable interdigital group number that is mated is not limited to the foregoing description.

In sum, the highly sensitive capacitive transducer that the utility model relates to, with the fixing interdigital and movable interdigital structure that is similar to the broach shape that comprises bottom and the plural lug boss that is connected with bottom vertical that is processed into, the equivalence that effectively increases capacitor plate changes area, cause rate of change of capacitance to increase, thereby improve the sensitivity that device is measured greatly.

The above only is a better embodiment of the present utility model; protection domain of the present utility model does not exceed with above-mentioned embodiment; as long as the equivalence that those of ordinary skills are done according to the utility model disclosure is modified or changed, all should include in the protection domain of putting down in writing in claims.

Claims (9)

1. highly sensitive capacitive transducer, it comprise flexible beam, fixing interdigital and is connected with flexible beam and with the fixation fork assignment close movably interdigital, it is characterized in that: described fixing interdigital and movably interdigital all comprise respectively bottom and the plural lug boss that is connected with described bottom vertical.

2. highly sensitive capacitive transducer according to claim 1 is characterized in that: described fixing interdigital and movable interdigital structure is identical.

3. highly sensitive capacitive transducer according to claim 1 is characterized in that: the shape of described fixing each lug boss on interdigital or movable interdigital is identical.

4. highly sensitive capacitive transducer according to claim 1 is characterized in that: the xsect of described lug boss is square.

5. highly sensitive capacitive transducer according to claim 1 is characterized in that: described lug boss big or small identical.

6. highly sensitive capacitive transducer according to claim 1 is characterized in that: the interval width of described per two lug bosses is identical.

7. highly sensitive capacitive transducer according to claim 1 is characterized in that: described fixing interdigital and movable interdigital mutual dislocation is arranged, and promptly described fixing interdigital lug boss is overlapped with movable interdigital lug boss.

8. highly sensitive capacitive transducer according to claim 1 is characterized in that: describedly fixing interdigitally comprise that first is fixing interdigital and second fixing interdigital, described first is fixing interdigital and second fix and interdigitally close the formation differential capacitance with the swinging fork assignment respectively.

9. highly sensitive capacitive transducer according to claim 8 is characterized in that: described first is fixing interdigital and second fix and interdigitally have two groups respectively.

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