CN1837765A - Pressure sensor employing thickness-cutting resonance for quartz crystal board - Google Patents

Abstract

This sensor comprises: a crystal sheet with thickness about 1mm and length within 10-40mm, an auxiliary metal sheet, and an end sheet with length within 10-40mm to fix other two sheets and bear environmental pressure. Wherein, using high tenacity viscose to the interfaces between different sheets, setting four bolts to fix them together; fixing whole sheet structure on two supports to keep the combined quartz crystal-auxiliary metal sheet on pure-bending state when forcing pressure on the end sheet top; plating thin-layer Ag-electrode on crystal surfaces; and holding space between crystal sheet and metal sheet. This invention has high sensitivity and well temperature stability.

Description

Pressure sensor employing thickness-cutting resonance for quartz crystal board

[technical field] the present invention relates to a kind of pressure transducer, particularly determines the pressure transducer of testing pressure according to the mensuration of quartz crystal plate frequency drift amount.

[background technology] quartz crystal plate have inclined to one side or environment that initial field exists in when vibrating, the original natural frequency of crystal slab can change, i.e. frequency drift, its size is fully by the decision of inclined to one side place.Because frequency drift amount ratio is easier to measure, calculates inclined to one side field and cause these environmental factors of field partially so people often drift about by survey frequency, as environmental pressure, temperature, inertial acceleration etc.Quartz pressure sensor just utilizes the frequency drift of measuring quartz resonator to determine environmental pressure just, being about to packaged quartz-crystal resonator is placed in the pressure environment, environmental pressure causes the initial field partially of appearance in the crystal, when allowing the quartz crystal panel vibration again, pressure partially field will cause the natural frequency of crystal slab and original natural frequency different.Under little inclined to one side hypothesis, pressure is directly proportional with the frequency drift amount, therefore, can instead release environmental pressure to be measured by the measurement to the frequency drift amount.

The common pressure sensor is made by quartz crystal plate, and its mode of operation has two kinds, promptly along the surface wave mode (SAW) of plane of crystal propagation and the bulk wave mode of propagating in whole crystal slab (BAW).In the bulk wave pressure transducer, the vibration usual thickness of crystal slab--shear mode.Because the bendind rigidity of plate is pressed rigidity much smaller than tension,, pressure will be parallel to plate face directive effect causes plate on the side compression deformation much larger than the pressure edge so vertically acting on the caused flexural deformation of plate face.Obviously, cause that by environmental pressure quartz plate flexural deformation comes the design pressure sensor, its sensitivity will be significantly improved.At present, the surface wave pressure transducer designed by this principle is applied in engineering, but also do not design successfully yet by the bulk wave pressure transducer of this principle work.Major obstacle is: inclined to one side of testing pressure caused bending in the AT-Cut quartz crystal plate is antisymmetric along neutral surface, promptly at the both sides of neutral surface material, on one side tension, pressurized on one side.Like this, quartz crystal plate is being made thickness--during scissoring vibration, equal zero by the resulting frequency drift amount of Tiersten first order perturbation integral and calculating.Here it is at present used bulk wave pressure transducer remain reason based on contraction principle in the pressure inducement quartz plate face, such pressure transducer has lower sensitivity.In addition, because bulk wave pressure transducer (BAW) specific surface wave pressure sensor (SAW) has higher frequency-temperature stability, therefore, cause that based on pressure the diastrophic bulk wave pressure transducer of quartz crystal plate has very important meaning.

[summary of the invention] the present invention will pass by environmental pressure " cause compression partially " in quartz crystal plate and change " causing inclined to one side of asymmetric curvature " into, promptly by introducing the metal accessory plate, make that the crooked field partially in the quartz crystal plate no longer is antisymmetric fully, thereby obtained quartz plate thickness--shear pressure sensor based on inclined to one side of bending.

Quartz crystal plate do not exist any when inclined to one side, thickness shear mode of oscillation U _NPairing natural frequency is designated as ω.After initial (remembering that initial bias placement field is w) partially occurring owing to Effect of Environmental in plate, this quartz crystal plate is again with mode U _NNatural frequency during vibration will become ω+Δ ω.According to the perturbation Integral Theory of Tiersten, the frequency drift amount is

$\frac{\mathrm{\Δ\ω}}{\mathrm{\ω}}\≅\frac{1}{2{\mathrm{\ω}}^2}\frac{{\∫}_V{\hat{c}}_{\mathrm{KLMN}}{U}_{L,K}{U}_{N,M}\mathrm{dV}}{{\∫}_V{\mathrm{\ρ}}_0{U}_N{U}_N\mathrm{dV}},---\left(1\right)$

In the formula,

${\hat{c}}_{\mathrm{KLMN}}={\mathrm{<figure-callout\; id="0"\; label="T\; KM"\; filenames="A20061003155500091.png"\; state="\{\{state\}\}">T</figure-callout>}}_{\mathrm{KM}}^{}{\mathrm{\&delta;}}_{\mathrm{LN}}+c_{\mathrm{KLMP}}{w}_{N,P}+c_{\mathrm{KPMN}}{w}_{L,P}+c_{\mathrm{KLMNAB}}{E}_{\mathrm{AB}}^0,---\left(2\right)$

${\mathrm{<figure-callout\; id="0"\; label="T\; IJ"\; filenames="A20061003155500091.png"\; state="\{\{state\}\}">T</figure-callout>}}_{\mathrm{IJ}}^{}=c_{\mathrm{<figure-callout\; id="0"\; label="IJKL\; E\; KL"\; filenames="A20061003155500091.png"\; state="\{\{state\}\}">IJKL</figure-callout>}}{E}_{\mathrm{KL}}^{}{}_0^{},{\mathrm{<figure-callout\; id="0"\; label="E\; KL"\; filenames="A20061003155500091.png"\; state="\{\{state\}\}">E</figure-callout>}}_{\mathrm{KL}}^{}=(w_{K,L}+w_{L,K})/2.$

In the above in two formulas, c _KLMPAnd c _KLMNABRepresent quartzy second order and three rank material coefficients, ρ respectively ₀The density of expression quartz crystal plate.In general, initial field partially is big more, and the frequency drift that then causes is just big more.Design in the past allowing quartz crystal plate partially field action and the pressure transducer that obtains by compression, because of the tension of quartz crystal plate presses the too big sensitivity of rigidity very low.The bending stiffness of considering crystal slab is much smaller than tension and compression rigidity, if can design a unitized construction that contains quartz crystal plate, this structure produces flexural deformation under the environmental pressure effect, and the inclined to one side field deformation in the quartz crystal plate is asymmetric words, so, this quartz crystal plate is again with thickness shear mode U _NThe frequency drift amount that frequency drift amount during vibration will the inclined to one side place of compression more in the past causes improves many.The present invention just is being based on this conception and is designing: bent with double panel structure integral body and bear the illustrated environments pressure p, double panel structure is made of a quartz crystal plate and a metal accessory plate, the accessory plate role is to guarantee crystal slab under tension or compression in the bending of doubling plate integral body, promptly bears inclined to one side of non-antisymmetry.Thereby can produce frequency drift, and realize measurement pressure by the caused thickness shear vibration of pressure p.Owing to be based on the frequency drift that the inclined to one side place of the bending of measuring doubling plate causes, so highly sensitive.In addition, what the crystal slab among the present invention was used is the quartz plate of AT one Cut, and does the thickness shear vibration, so the temperature stability of this pressure transducer is good.

The present invention mainly comprises: quartz crystal plate, assistant metal plate, the end panel that is used for fixing two plates and bears environmental pressure, the length of quartz crystal plate and end panel is the 10-40 millimeter, about 1 millimeter of quartz crystal plate thickness.When connecting end panel and quartz crystal plate and assistant metal plate, except along the interface between them is used the seccotine adhesion, also use four bolts together with their bolts, whole plate structure is fixed on two bearings.Under environmental pressure p effect, be positioned at two combination quartz crystal-assistant metal plate structures between bearing and be in the simple bending state.In addition, upper and lower two surfaces of quartz crystal plate all are coated with the thin layer silver electrode, between quartz crystal plate and assistant metal plate microvoid are arranged.

The linearity of quartz crystal and nonlinear elasticity property coefficient are:

c ₁₁＝c ₂₂＝86.74，c ₂₁＝6.99，c ₆₆＝39.88×10 ⁹N/m ²；

c ₆₆₁＝(-2c ₁₁₁-c ₁₁₂+3c ₂₂₂)/4；c ₆₆₂＝(2c ₁₁₁-c ₁₁₂-c ₂₂₂)/4；(3)

c ₁₁₁＝-2.1，c ₁₁₂＝-3.45，c ₂₂₂＝-3.32×10 ¹¹N/m ².

$\frac{\mathrm{\&Delta;\&omega;}}{\mathrm{\&omega;}}=\frac{3}{4}c\frac{(b/a)\&CenterDot;(b/h_2)}{2{({\mathrm{<figure-callout\; id="1"\; label="h"\; filenames="A20061003155500071.png"\; state="\{\{state\}\}">h</figure-callout>}}_1/a)}^2+2{({\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="A20061003155500082.png"\; state="\{\{state\}\}">h</figure-callout>}}_2/a)}^2+3({\mathrm{<figure-callout\; id="1"\; label="h"\; filenames="A20061003155500071.png"\; state="\{\{state\}\}">h</figure-callout>}}_1/a+{\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="A20061003155500082.png"\; state="\{\{state\}\}">h</figure-callout>}}_2/a)}\&CenterDot;\frac{\mathrm{<figure-callout\; id="2"\; label="p\; E"\; filenames="A20061003155500082.png"\; state="\{\{state\}\}">p</figure-callout>}}{E_{}},$

${\mathrm{<figure-callout\; id="2"\; label="E"\; filenames="A20061003155500082.png"\; state="\{\{state\}\}">E</figure-callout>}}_2=c_{11}-c_{12}^2/c_{22},---\left(4\right)$

$c=2+\frac{c_{661}}{c_{66}}-\frac{c_{662}{c}_{21}}{c_{66}{c}_{22}}.$

P represents environmental pressure in the formula, c ₁₁, c ₁₂, c ₂₂, c ₆₆, c ₆₆₁, c ₆₆₂Second order and the three rank elasticity coefficient of representing quartz crystal plate respectively, h ₁, h ₂The thickness of representing assistant metal plate and quartz crystal plate respectively, 2a, b represent the length of quartz crystal plate and end panel respectively.

Can find from following formula: all give regularly the sensitivity of pressure transducer, i.e. Δ ω/ω and p/E in the parameter of quartz crystal plate ₂Ratio, increase with the increase of b/a, with h ₁/ h ₂Increase and reduce.Find by calculating again: the length to height ratio of quartz crystal plate is big more, and then sensitivity is high more again; The assistant metal plate is hard more, and then sensitivity is high more; And the pressure transducer remolding sensitivity traditional type pressure transducer of design improves more than at least four times like this.

The present invention compares with existing pressure transducer and has the following advantages: highly sensitive, temperature stability is good.

[description of drawings]

Fig. 1 is for the present invention is based on diastrophic pressure transducer synoptic diagram;

Fig. 2 is for the present invention is based on diastrophic pressure transducer vertical view;

Fig. 3 is suffered internal force on quartz plate of the present invention and the metal accessory plate xsect;

Fig. 4 for the present invention with based on the remolding sensitivity of the pressure transducer of the inclined to one side place of compression design in the past;

Fig. 5 is the influence of the accessory plate of different metal material manufacturing to pressure transducer sensitivity;

Fig. 6 is the influence of the different quartz crystal plate length to height ratio of the present invention to pressure transducer sensitivity.

[embodiment] as depicted in figs. 1 and 2, the present invention is made up of quartz crystal plate 1, assistant metal plate 2 and the end panel 3 that is used for fixing two plates and bears environmental pressure p, end panel 3 is hard more than plate 1 and 2.When connecting end panel 3,, also use four bolts 4 together with their bolts except along the interface between them is used the seccotine adhesion with quartz crystal plate 1 and assistant metal plate 2.Whole plate structure is fixed on two bearings 5, so that under the p effect, is positioned at that two combination quartz crystals between bearing--the assistant metal plate structure is in the simple bending state.In addition, upper and lower two surfaces of quartz crystal plate all are coated with thin layer silver electrode 6, between quartz crystal plate and assistant metal plate microvoid 7 are arranged.Selected rectangular coordinate system X ₁X ₂X ₃, X wherein ₁The axle along its length, X ₂Axle faces down X perpendicular to plate ₃Axle and X ₁X ₂Face is vertical.The last plane of end panel 3 is subjected to environmental pressure p effect, causes to be positioned at | X ₁| the combination quartz crystal in＜a interval--the assistant metal plate structure is in the simple bending state.Analyze | X ₁| behind the internal force diagram 3 on the quartz crystal plate in＜a interval and the assistant metal plate xsect as can be known: under the effect of p power, produce compression-crooked combined deformation in the quartz crystal plate, promptly the inclined to one side field in the quartz crystal plate will be by N and M ₂The associating generation is so can design a tension or pressure in the quartz crystal plate.In addition, inclined to one side in the metal accessory plate also will be by N and M ₁The associating generation.In boundary condition, because end panel 3 is more many firmly than plate 1 and 2, so be positioned at | X ₁| the combination quartz crystal in＜a interval--assistant metal plate structure is in the simple bending state just as a unjointed beam, so the two is at X ₁The corner at=± a place can be taken as approximately equal.The neutral line of unitized construction, the thickness by suitable design sheet metal can make the neutral line of combination beam be positioned at the intermediate gaps scope.Usually, the thickness in the space 7 between quartz plate and the metal accessory plate is very little, can ignore in analysis.Like this, the orlop of metal accessory plate and the superiors of quartz plate should be similar to and be in the neutral line position, promptly should not have stretching or compress to take place in the place.Design after the structural parameters, promptly available beam theory calculates inclined to one side in the quartz plate.Then, again at quartz plate along X ₁Apply thickness shear vibration U on the direction _NFrequency after inclined to one side of note occurs is ω+Δ ω, and Δ ω is relevant with p.Separate and U the field partially _NSubstitution (1) formula can solve p by Δ ω.

Under identical physical dimension, the present invention and two kinds are based on the sensitivity comparison diagram of compression pressure transducer partially as shown in Figure 4.Wherein, first kind of pressure transducer is meant that one is placed in the cylindrical drum than feldspar Britain side plate, and the p effect that is stressed of round metal column casing shell is shunk, thereby produces inclined to one side of the compression of quartz crystal plate; Second kind of pressure transducer is meant that a thin quartzy plectane is placed in the cylindrical drum, and the p effect that is stressed of round metal column casing shell is shunk, thereby produces the inclined to one side field of the compression of quartz crystal plate; The third pressure transducer promptly is the present invention.Relatively as seen: pressure transducer sensitivity of the present invention will be apparently higher than the above two.

With different metal material Al, Cu, when W or alloy steel were made accessory plate, the sensitivity of pressure transducer was different.As can be seen from Figure 5: accessory plate is hard more, and transducer sensitivity is high more.The length to height ratio of English crystal slab is also influential to transducer sensitivity: as can be seen from Figure 6: the length to height ratio of quartz crystal plate is big more, is easy to generate crooked field partially more, and sensitivity is also just high more.

Claims (5)

1. pressure sensor employing thickness-cutting resonance for quartz crystal board, comprise quartz crystal plate, it is characterized in that: on quartz crystal plate, arrange an assistant metal plate, with connecting end plate environmental pressure is fixed and born to two plates, to connect end panel and quartz crystal plate and assistant metal plate with seccotine pastes, and with their bolts together with bolt, whole plate structure is fixed on two bearings, upper and lower two surfaces of quartz crystal plate all are coated with the thin layer silver electrode, between quartz crystal plate and assistant metal plate microvoid are arranged.

2. pressure transducer according to claim 1 is characterized in that: the length of described quartz crystal plate and end panel is the 10-40 millimeter.

3. pressure transducer according to claim 1 and 2 is characterized in that: the neutral axis when combination quartz crystal-assistant metal plate structure is crooked is positioned at microvoid.

4. pressure transducer according to claim 1 and 2 is characterized in that: the crooked frequency drift and the relational expression between the environmental pressure of the pressure transducer of field partially are:

$\frac{\mathrm{\&Delta;\&omega;}}{\mathrm{\&omega;}}=\frac{3}{4}c\frac{(b/a)\&CenterDot;(b/h_2)}{2{(h_1/a)}^2+2{(h_2/a)}^2+3(h_1/a+h_2/a)}\&CenterDot;\frac{p}{E_2},$

$E_2=c_{11}-c_{12}^2/c_{22},$

$c=2+\frac{c_{661}}{c_{66}}-\frac{c_{662}{c}_{21}}{c_{66}{c}_{22}}.$

Wherein, ω, Δ ω represent natural frequency and drift frequency respectively, and p represents environmental pressure, c ₁₁, c ₁₂, c ₂₂, c ₆₆, c ₆₆₁, c ₆₆₂Second order and the three rank elasticity coefficient of representing quartz crystal plate respectively, h ₁, h ₂The thickness of representing assistant metal plate and quartz crystal plate respectively, 2a, b represent the length of quartz crystal plate and end panel respectively.

5. pressure transducer according to claim 1 and 2 is characterized in that: the material of described assistant metal plate is metal or alloy steel such as aluminium, copper or tungsten.

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