CN204759383U - Induction type touch -sensitive screen - Google Patents

Abstract

The utility model discloses an induction type touch -sensitive screen, including the touch layer that has top surface and bottom surface, be connected to touch layer bottom surface's pressure sensor array and touch -control perception sensor, the the control unit who is connected respectively with pressure sensor array and touch -control perception sensor, the touch -sensitive screen shell of constituteing by basement and periphery, pressure sensor includes the control unit, ring electric capacity unique tuple and the strip electric capacity unique tuple be connected respectively with the control unit, ring electric capacity unique tuple is used for surveying the size of tangential force and normal force, strip electric capacity unique tuple is used for measuring the direction of tangential force, strip electric capacity unique tuple sets up the four corners of base plate outside ring electric capacity unique tuple, the touch stratification is in the touch -sensitive screen shell, touch layer and periphery directly are equipped with the buffer layer of compriseing elastic material, the control unit includes touch -control action the control unit, position acquisition control unit, the main control unit of being connected with touch -control behavioral control unit and position acquisition control unit respectively.

Description

Induction type touch screen

Technical Field

The utility model belongs to the technical field of the touch-sensitive screen, a induction type multi-point touch screen is related to, concretely relates to induction type multi-point touch screen based on three-dimensional capacitive pressure sensor.

Background

The capacitive touch sensor has the advantages of simple structure, low manufacturing cost, high sensitivity, good dynamic response and the like, and particularly has stronger adaptability to severe conditions such as high temperature, radiation, strong vibration and the like. However, this type of sensor output typically exhibits non-linearity, and both the inherent parasitic and distributed capacitances can have an effect on the sensitivity and measurement accuracy of the sensor. Since the last 70 s, with the development of integrated circuit technology, capacitive sensors packaged together with micro-measuring instruments appeared, and the novel sensors can greatly reduce the influence of distributed capacitance and overcome the inherent defects of the sensors. The capacitive touch sensor is a sensor with extremely wide application and great development potential. The pressure sensors all only collect pressure in the vertical direction: for example, the Chinese patent CN201110074892.6 adopts 10 film pressure sensors corresponding to sole pressure distribution points; CN201010230489.3 uses a matrix pressure sensor of 8 columns × 10 rows, and CN2012102984097 uses a matrix of 40 by 40 piezoresistors, which cannot be used for three-dimensional force calculation.

Disclosure of Invention

According to the not enough of above prior art, the utility model provides an induction type multi-point touch screen, through adopting three-dimensional capacitive pressure sensor, can in time accurate response a plurality of touches of taking place simultaneously to and the pressure and the orbit of every electric shock of accurate record.

In order to realize the purpose, the utility model discloses the technical scheme who takes does: an inductive touch screen comprising a touch layer having a top surface and a bottom surface, an array of pressure sensors connected to the bottom surface of the touch layer, a control unit connected to the array of pressure sensors, a touch screen housing comprised of a base and a periphery, the touch layer being disposed in the touch screen housing, the touch layer and the periphery being directly provided with a buffer layer comprised of an elastomeric material, the array of pressure sensors connected to the bottom surface of the touch layer being such that a touch pressure applied to the top surface is transmitted to the pressure sensors near the location of the touch pressure. The touch layer is formed of an elastic material and has a characteristic of isolating moisture and dust, while the touch layer has sensitivity and accuracy to touch. The control unit comprises a touch behavior control unit, a position acquisition control unit and a main control unit connected with the touch behavior control unit and the position acquisition control unit respectively, the position acquisition control unit is used for acquiring touch points and touch positions, and the touch behavior unit detects whether a touch behavior exists on the touch screen.

The touch sensing sensor comprises an X-direction differential capacitance unit combination and a Y-direction differential capacitance unit combination, is arranged at an end corner of the touch screen, and is connected with the touch behavior control unit, and the sensitivity of the touch sensing sensor is higher than that of the pressure sensor. The touch sensing sensors at the end corners of the control unit are in a working state, and the pressure sensor array is in a low power consumption state. The touch sensing sensor is arranged to avoid abnormal touch or induction response and reduce power consumption. The touch perception sensors are at least arranged to be 4, 2 capacitance units are respectively formed into an X-direction differential capacitance unit combination and a Y-direction differential capacitance unit combination, and the increase of the arrangement number is beneficial to improving the detection reliability of the touch screen. In this embodiment, 4 capacitor units are respectively set up at 4 end corners of the screen body, and if the number of the capacitor units exceeds 4, the capacitor units may be set up at the end edge or the side edge.

The pressure sensor comprises a control unit, a ring capacitor unit group and a strip capacitor unit group, wherein the ring capacitor unit group and the strip capacitor unit group are respectively connected with the control unit, the ring capacitor unit group is used for measuring the tangential force and the normal force, the strip capacitor unit group is used for measuring the direction of the tangential force, and the strip capacitor unit group is arranged at four corners of an outer substrate of the ring capacitor unit group. The touch sensing sensor comprises an X-direction differential capacitance unit combination and a Y-direction differential capacitance unit combination, is arranged at an end corner of the touch screen, and is connected with the touch behavior control unit, and the sensitivity of the touch sensing sensor is higher than that of the pressure sensor array. The ring capacitor unit group includes that ring capacitor unit is right more than two pairs, ring capacitor unit is right including two ring capacitor unit, strip capacitor unit group includes X direction differential capacitor unit group and Y direction differential capacitor unit group, and X direction differential capacitor unit group and Y direction differential capacitor unit group all include the differential capacitor unit module of mutual formation more than two, the capacitor unit module is the broach structure of constituteing by the strip capacitor unit more than two, and every ring capacitor unit and strip capacitor unit all include the drive electrode of polar plate and the response electrode of bottom plate. The induction electrode and the driving electrode of each circular ring capacitor unit are opposite and same in shape, the driving electrode and the induction electrode of each strip capacitor unit are same in width, the length of the driving electrode of each strip capacitor unit is larger than that of the induction electrode, and left difference delta is reserved at two ends of the length of the driving electrode of each strip capacitor unit_{Left side of}And the right difference position delta_{Right side}，b_{0 drive}＝b_{Feeling of 0}+δ_{Right side}+δ_{Left side of}Wherein b is_{0 drive}Length of the driving electrode of the strip-shaped capacitor unit, b_{Feeling of 0}Is the length of the induction electrode of the strip-shaped capacitor unit, and the left difference position delta of the strip-shaped capacitor unit_{Left side of}Right difference delta_{Right side}And is andwherein d is₀Is the thickness of the elastic medium, G is the shear modulus, τ, of the elastic medium_maxThe maximum stress value. The circular ring capacitor sheetThe tuple comprises n concentric rings of capacitor cells, whereina_{Flat plate}Length of parallel plate, r_{Round (T-shaped)}Is the width of the ring capacitor unit, a_{Delta circle}And the electrode distance between two adjacent circular capacitor units. The width r of the concentric ring capacitor unit_{Round (T-shaped)}And the width a of the strip-shaped capacitor unit₀Equal; electrode spacing a of strip-shaped capacitor unit_{Delta bar}And the electrode spacing a of the circular ring capacitor unit_{Delta circle}Equal, width of the strip-shaped capacitor unitWherein d is₀E is the Young's modulus of the elastic medium, and G is the shear modulus of the elastic medium.

A supporting layer is arranged between the touch screen shell substrate and the touch position pressure sensor and the touch behavior pressure sensor, and the supporting layer is made of materials with shock absorption characteristics.

The utility model has the advantages that in order to improve the sensitivity of the contact type capacitance three-dimensional force sensor, the conversion precision and the reliability and the stability of the robot touch sensing system, a dielectric layer which takes a PCB as a parallel plate electrode and PDMS as a base material is designed, and the plane size is 10 multiplied by 10mm²The combined capacitance sensitive device of (1). The input and output characteristics of the normal and tangential stress tensor sensitive units and corresponding linearity and sensitivity formulas thereof are deduced. Based on the above and referring to the mature device manufacturing process, the sensing unit with the comb-shaped electrode is provided, and the electrode plane design of differential combination and summation combination is realized on the surface of the polar plate, so that the normal and tangential conversion achieves higher linearity, precision and sensitivity. In the design index, the normal sensitivity and the tangential sensitivity of capacitance conversion can reach 810fF/N, and a novel, convenient and flexible device selection is provided for a robot touch sensor system.

Drawings

The contents of the drawings and the reference numerals in the drawings are briefly described as follows:

fig. 1 is a plan view of a touch panel according to an embodiment of the present invention.

Fig. 2 is a sectional view of a structure of a touch panel according to an embodiment of the present invention.

Fig. 3 is an area analysis diagram of the offset and dislocation of the concentric rings according to the embodiment of the present invention.

Fig. 4 is an analysis diagram of the outer concentric ring dislocation versus the outer diameter circle according to the embodiment of the present invention.

Fig. 5 is a plan view of a parallel plate capacitor according to an embodiment of the present invention.

Fig. 6 is a structural diagram of a drive electrode according to an embodiment of the present invention.

Fig. 7 is a rectangular coordinate system of the flat capacitor plate according to the embodiment of the present invention.

Fig. 8 is a structural diagram of two sets of circular capacitor sets according to an embodiment of the present invention.

Fig. 9 is an initial misalignment map of a differential strip capacitor cell according to an embodiment of the present invention.

Fig. 10 is a diagram illustrating the offset of the differential strip capacitor unit after being stressed according to the embodiment of the present invention.

Fig. 11 is a schematic signal differential diagram of a unit capacitor pair according to an embodiment of the present invention.

Fig. 12 is a cross-sectional structure of a parallel plate capacitor according to an embodiment of the present invention.

The PCB comprises an upper PCB substrate 1, a lower PCB substrate 2, a driving electrode 3, a sensing electrode 4, an elastic medium 5 and a plurality of electrodes.

Detailed Description

The following description of the embodiments with reference to the drawings is intended to illustrate the present invention in further detail, such as the shapes and structures of the components, the mutual positions and connections between the components, the functions and working principles of the components, the manufacturing process, and the operation and use methods, etc., so as to help those skilled in the art understand the present invention more completely, accurately and deeply.

As shown in fig. 1 and 2, an inductive multi-touch screen includes a touch layer having a top surface and a bottom surface, a pressure sensor array and a touch sensor connected to the bottom surface of the touch layer, a control unit connected to the pressure sensor array and the touch sensor array, and a touch screen housing composed of a substrate and a periphery, wherein the touch layer is disposed in the touch screen housing, the touch layer and the periphery are directly provided with a buffer layer composed of an elastic material, the control unit includes a touch behavior control unit, a position acquisition control unit, and a main control unit connected to the touch behavior control unit and the position acquisition control unit, the position acquisition control unit is used for acquiring touch points and touch positions, and the touch behavior unit detects whether a touch behavior exists on the touch screen. The touch sensing sensor comprises an X-direction differential capacitance unit combination and a Y-direction differential capacitance unit combination, is arranged at an end corner of the touch screen, and is connected with the touch behavior control unit, and the sensitivity of the touch sensing sensor is higher than that of the pressure sensor array. The three-dimensional capacitive pressure sensor of pressure sensor, pressure sensor include the control unit, with the ring electric capacity unit group and the strip electric capacity unit group that the control unit is connected respectively, the ring electric capacity unit group is used for surveying the size of tangential force and normal force, the strip electric capacity unit group is used for measuring the direction of tangential force, the strip electric capacity unit group sets up the four corners at ring electric capacity unit group outer base plate. The touch sensing sensorThe touch sensing device comprises an X-direction differential capacitance unit combination, a Y-direction differential capacitance unit combination, a touch behavior control unit and a touch sensing sensor, wherein the X-direction differential capacitance unit combination and the Y-direction differential capacitance unit combination are arranged at end corners of a touch screen, and the touch sensing sensor has higher sensitivity than a pressure sensor array. The ring capacitor unit group includes that ring capacitor unit is right more than two pairs, ring capacitor unit is right including two ring capacitor unit, strip capacitor unit group includes X direction differential capacitor unit group and Y direction differential capacitor unit group, and X direction differential capacitor unit group and Y direction differential capacitor unit group all include the differential capacitor unit module of mutual formation more than two, the capacitor unit module is the broach structure of constituteing by the strip capacitor unit more than two, and every ring capacitor unit and strip capacitor unit all include the drive electrode of polar plate and the response electrode of bottom plate. The induction electrode and the driving electrode of each circular ring capacitor unit are opposite and same in shape, the driving electrode and the induction electrode of each strip capacitor unit are same in width, the length of the driving electrode of each strip capacitor unit is larger than that of the induction electrode, and left difference delta is reserved at two ends of the length of the driving electrode of each strip capacitor unit_{Left side of}And the right difference position delta_{Right side}，b_{0 drive}＝b_{Feeling of 0}+δ_{Right side}+δ_{Left side of}Wherein b is_{0 drive}Length of the driving electrode of the strip-shaped capacitor unit, b_{Feeling of 0}Is the length of the induction electrode of the strip-shaped capacitor unit, and the left difference position delta of the strip-shaped capacitor unit_{Left side of}Right difference delta_{Right side}And is andwherein d is₀Is the thickness of the elastic medium, G is the shear modulus, τ, of the elastic medium_maxThe maximum stress value. The ring capacitor unit group comprises n concentric ring capacitor unitsWherein, a_{Flat plate}Length of parallel plate, r_{Round (T-shaped)}Is the width of the ring capacitor unit, a_{Delta circle}And the electrode distance between two adjacent circular capacitor units. The width r of the concentric ring capacitor unit_{Round (T-shaped)}And the width a of the strip-shaped capacitor unit₀Equal; electrode spacing a of strip-shaped capacitor unit_{Delta bar}And the electrode spacing a of the circular ring capacitor unit_{Delta circle}Equal, width of the strip-shaped capacitor unitWherein d is₀E is the Young's modulus of the elastic medium, and G is the shear modulus of the elastic medium. A supporting layer is arranged between the touch screen shell substrate and the touch position pressure sensor and the touch behavior pressure sensor, and the supporting layer is made of materials with shock absorption characteristics.

A control method of an induction type multi-point touch screen is characterized by comprising the following steps: after the equipment is started, a touch behavior control unit of a control unit acquires a value of a touch behavior pressure sensor, a sensor array is in a dormant state, and when the value of the touch behavior pressure sensor changes; secondly, capacitance collection is carried out on a capacitance unit of the pressure sensor array, and a position collection control unit collects touch points and touch positions for collected data analysis; thirdly, the main control unit groups the capacitor units according to the number of touch points and the touch positions to respectively form touch point capacitor groups formed by combining the X-direction differential capacitor units and the Y-direction differential capacitor units; calculating the coordinates and the running track of the touch position of the touch point according to the data of the touch point capacitor group; and step four, outputting the calculated data.

The coordinates of the touch position of the touch point in the third step pass through the steps of: step a, setting the coordinate of the touch point as (x)_j，y_j) Where j is 1, 2, …, M is a known number of touch points, and the coordinates of the capacitive unit associated with a touch point are (a)_i，b_i) Where i is 1, 2, …, N is the known number of touch points, N is the known number of associated capacitive units, $(x_j,y_j)-(a_i,b_i)=\sqrt{{(x_j-a_i)}^2-{(y_j-b_i)}^2};$ b, respectively listing touch points and associated capacitance distance equations, and solving coordinates of the touch points according to intersection points of circles, of which the touch points are any two relevant points and the distances are the radii; and c, calculating according to the output value of the touch point capacitor bank, and calculating the size and the direction of the pressure and the movement track of the pressure.

And c, calculating the movement track in the step c, performing calculus by pressure to obtain the movement track, accumulating the movement track by the change of each capacitance unit of the touch point, and determining the movement time in each direction by the change of the capacitance value of each capacitance unit.

The derivation and principle of the present invention, the shape, structure, mutual position and connection relationship between the parts, the function and operation principle of the parts, the manufacturing process and operation method, etc. will be described in further detail with reference to fig. 3-12.

1.1 capacitance formula and input-output characteristics thereof

The initial capacitance of the parallel plates is:

$C_0=\frac{{\mathrm{\ϵ}}_0.{\mathrm{\ϵ}}_r\·A_0}{d_0}---\left(1\right)$

in the formula, epsilon₀The electric constant of the vacuum medium is 8.85PF/m, epsilon_r2.5 is the relative permittivity of the dielectric, a₀The initial facing area of the upper and lower polar plates. d₀Receive sigma_nIs excited to produce a relative deformation epsilon_n＝δ_n/d₀＝σ_nAnd E, substituting the formula (1) to obtain the input-output characteristics

$C_n={\mathrm{\ϵ}}_0.{\mathrm{\ϵ}}_r\frac{A_0}{d_0(1-{\mathrm{\ϵ}}_n)}={\mathrm{\ϵ}}_0\·{\mathrm{\ϵ}}_r\frac{A_0}{d_0(1-\frac{F_n}{AE})}---\left(2\right)$

1.2 Linearity and sensitivity under Normal stress

1.2.1 Normal Linearity

(2) In the formula F_nIn the denominator, therefore C_n＝f(F_n) The relationship of (a) is non-linear. Maximum value sigma in the range of conversion_nmaxε compared with the dielectric elastic constant E_nIs a very small quantity, i.e. epsilon in the denominator_n<<1, expanding the formula (2) according to a series, and omitting high-order infinitesimal more than the square, which can be simplified as follows:

$C_n=C_0(1+\mathrm{\&epsiv;})=C_0(1+\frac{F_n}{A\&CenterDot;E})---\left(3\right)$

can be seen in C_nAnd F_nThe maximum relative error of the normal linearity in the conversion characteristic of (a) is close to zero.

1.2.2 sensitivity

Definition of sensitivity by Normal

According to the formula (2)

$S_{n2}=\frac{{\mathrm{dC}}_n}{{\mathrm{dF}}_n}=C_0\&CenterDot;\frac{1}{1-2\mathrm{\&epsiv;}}=C_0\&CenterDot;\frac{1}{1-2\frac{F_n}{A\&CenterDot;E}}---\left(4\right)$

The linear sensitivity can be obtained according to the formula (3),

S_n1＝C₀/AE＝ε₀ε_r/d₀E(5)

S_n2with F_nAnd is changed to F_nThe greater, S_n2The larger, the slightly non-linear over the entire conversion characteristic.

1.3 relationship between tangential displacement and effective area of circular ring capacitor

Analysis was performed for concentric ring capacitance pairs, as shown in FIG. 3, R₁Is the outer radius of the circle, R₂The radius of the inner circle, R equals the width of the ring, and equals the radius of the large outer circle R₁Inner circle radius R₂. Force F on a section of the drive electrode_xCausing a shear dislocation between the corresponding driving and sensing electrodes, and d_xThe displacement of the tangent plane and the dislocation area are S_{Inner part}And S_{Outer cover}The initial facing area of the electrode plate should be pi (R)₁ ²-R₂ ²). FIG. 4 is an analysis graph of capacitance of an outer concentric ring versus an outer diameter circle, where the distance between the centers of the two circles before and after movement is d_xThe intersection point of the two circle centers and the two circles forms a rhombus before and after moving, and S can be calculated_{Outer cover}Area of (d):

in the above formula, there is d_x<<R₁To thereby obtain

By

Will be provided withAnd the high-order terms are omitted,

similarly, it can be known that S_{Inner part}＝2R₂d_xTherefore, the error area of the concentric ring capacitor is S-2R₁d_x+2R₂d_x。

1.4 capacitance Change of the Ring capacitive cell group under tangential stress τ excitation

The tangential stress tau does not change the geometric size parameter A of the polar plate₀To the thickness d of the medium₀Nor is it affected. However tau_xAnd τ_yThe spatial structure of the parallel plate capacitor is changed, and dislocation offset occurs between the upper and lower electrode plates facing in the forward direction. Dislocation deviation d of polar plate under action of tau_x. When tau is zero, the upper and lower electrodes of the circular ring capacitor unit are opposite, and the effective section between the upper and lower electrodesIn FIG. 4, at τ_xUnder the action of right direction, the upper polar plate is displaced to right relative to the lower polar plate_xThereby the effective area between the upper and lower polar plates is calculated when the capacitance is calculated $A_{\mathrm{\&tau;}}={\mathrm{\&pi;R}}_1^2-{\mathrm{\&pi;R}}_2^2-2R_1{d}_x-2R_2{d}_x,$ The resulting capacitance is:

$C_{\mathrm{\&tau;}x}\frac{{\mathrm{\&epsiv;}}_0.{\mathrm{\&epsiv;}}_r\&CenterDot;({\mathrm{\&pi;R}}_1^2-{\mathrm{\&pi;R}}_2^2-2R_1{d}_x-2R_2{d}_x)}{d_0}---\left(6\right)$

according to shear Hooke's law

τ_x＝γ_x·G＝G·δ_x/d₀(7)

Substituting (7) into (6) to obtain

$C_{\mathrm{\&tau;}x}=C_0-\frac{{\mathrm{\&epsiv;}}_0.{\mathrm{\&epsiv;}}_r\&CenterDot;2(R_1+R_2)d_x}{d_0}=C_0-\frac{{\mathrm{\&epsiv;}}_0.{\mathrm{\&epsiv;}}_r\&CenterDot;2(R_1+R_2)F_x}{A_{\mathrm{\&tau;}}G}=C_0-\frac{2{\mathrm{\&epsiv;}}_0.{\mathrm{\&epsiv;}}_r{F}_x}{G\mathrm{\&pi;}(R_1-R_2)}---\left(8\right)$

(8) The formula is the input-output characteristic under shear stress, C_τAnd τ_xIn a linear relationship, its sensitivity

$S_{\mathrm{\&tau;}x}=\frac{{\mathrm{dC}}_{\mathrm{\&tau;}}}{{\mathrm{dF}}_x}=\frac{2{\mathrm{\&epsiv;}}_0\&CenterDot;{\mathrm{\&epsiv;}}_r}{G\mathrm{\&pi;}(R_1-R_2)}---\left(9\right)$

From equation (9), the tangential sensitivity and R can be seen₁-R₂In relation to this, the tangential sensitivity is inversely proportional to the width of the ring, the smaller the width the higher the sensitivity.

Design of 2-plate capacitor

2.1 design of Flat capacitors

See the electrode plan layout in FIG. 5 and the block diagram of the drive electrode in FIG. 6, at a 10X 10mm thickness²The circular ring type contact parallel plate three-dimensional pressure sensor on the substrate comprises a control unit, a circular ring capacitance unit group and a strip capacitance unit group, wherein the circular ring capacitance unit group and the strip capacitance unit group are respectively connected with the control unit, the circular ring capacitance unit group is used for measuring the tangential force and the normal force, the strip capacitance unit group is used for measuring the direction of the tangential force, and the strip capacitance unit group is arranged at four corners outside the circular ring capacitance unit group of the substrate. Therefore, the area of the parallel plates can be effectively used, the circular capacitor unit group is paved on the whole parallel plate, the circular capacitor unit group plays a role in measuring the three-dimensional force, and the strip-shaped capacitor unit group effectively utilizes the space at four corners of the parallel plate after the circular capacitor unit group is paved, and is used for measuring the direction of the three-dimensional force tangential force. The driving electrode and the induction electrode of the circular ring capacitor unit group are both composed of n concentric circular rings, and n is an even number, so that an n/2 circular ring capacitor unit pair is formed. The hatched portions represent the outer mold sections of the lost wax casting process, which geometry and dimensions should also be precise during mechanical forming.

Referring to the rectangular coordinate system of the flat capacitor of fig. 7, the origin of the coordinate system is at the origin of the concentric circles of the circular capacitor unit groups, the X-axis and the Y-axis are along the diagonal direction of the flat capacitor, the X-direction differential capacitor unit group includes an X-direction differential capacitor unit group i and an X-direction differential capacitor unit group iii, the X-direction differential capacitor unit group i and the X-direction differential capacitor unit group iii are respectively located on the positive and negative half shafts of the X-axis and are symmetrical along the Y-axis, and the Y-direction differential capacitor unit group includes a Y-squareThe Y-direction differential capacitor unit group II and the Y-direction differential capacitor unit group IV are respectively positioned on the positive half shaft and the negative half shaft of the Y-axis and are symmetrical along the X-axis, and the X-direction differential capacitor unit group I and the X-direction differential capacitor unit group III form a pair tau_xThe differential capacitor unit group II and the differential capacitor unit group IV form a pair tau_yA responsive differential capacitive cell combination.

The ring capacitor unit group comprises n concentric ring capacitor unitsWherein, a_{Flat plate}Length of parallel plate, r_{Round (T-shaped)}Is the width of the ring capacitor unit, a_{Delta circle}And the electrode distance between two adjacent circular capacitor capacitors. The capacitor unit module adopts a comb-tooth structure, the X-direction differential capacitor unit group and the Y-direction differential capacitor unit group both comprise m strip-shaped capacitor units,wherein, a_{Delta bar}An electrode distance a is arranged between two adjacent strip-shaped capacitor units₀The width of the strip-shaped capacitor unit. Width r of concentric ring capacitor unit_{Round (T-shaped)}And the width a of the strip-shaped capacitor unit₀Equal; electrode spacing a of strip-shaped capacitor unit_{Delta bar}And the distance a between the electrodes of the circular capacitor_{Delta circle}Equal, width of the strip-shaped capacitor unitWherein d is₀E is the Young's modulus of the elastic medium, and G is the shear modulus of the elastic medium.

2.2 excitation Signal and coordinate System

Placing the circular capacitor unit in a rectangular coordinate system shown in fig. 7, applying three-dimensional excitation to the outer surface of the capacitor plate to generate contact force having Fx, Fy andthree directional components of Fz, the acting directions of Fx and Fy are along X-axis and Y-axis, the acting direction of Fz is along OZ-axisThe direction, normal direction and tangential direction stress are both stress tensors, and the response of capacitance can be output from the lead wires of the electrodes; normal stress sigma_nFn/A, whereinThe pole plate is a normal force bearing surface, and Fn is a normal component; generating paired tangential stresses tau on both side surfaces_{Cutting machine}＝F_{Cutting machine}/A。

According to Hooke's law, σ, in elastic mechanics_nAnd τ_x，τ_yA corresponding deformation of the elastomer will occur. Wherein,

${\mathrm{\&sigma;}}_n=E\&CenterDot;{\mathrm{\&epsiv;}}_n=E\&CenterDot;{\mathrm{\&delta;}}_n/d_0=\frac{F_n}{A}$

wherein E is the Young's modulus GN/m of the elastic medium²G is the shear modulus GN/m of the elastic medium²δ n is the normal displacement (unit: mum) of the elastic medium, and δ x and δ y are the relative dislocation of the upper and lower electrode plates of the circular ring capacitor unit(unit: μm), the sign of which is determined by the orientation of the coordinate axis.

2.3 calculation of Normal and tangential force magnitudes

And selecting the nth ring capacitor unit and the nth/2 ring capacitor unit, and calculating a composition equation set by establishing the ring capacitor units, as shown in fig. 8. After the electrode plate is subjected to normal and tangential excitation, the output capacitance of the nth circular ring capacitance unit is set as C₁N/2 ring capacitor units with output capacitance of C₂Tangential displacement of d_xNormal capacitance pole distance of d_n，S₁₀Is the initial facing area of the outer ring, S₂₀Is the initial facing area of the inner ring.

$C_1=\frac{\mathrm{\&epsiv;}(S_{10}-S1)}{d_n}=\frac{\mathrm{\&epsiv;}({\mathrm{\&pi;R}}_1^2-{\mathrm{\&pi;R}}_2^2)}{d_n}-\frac{\mathrm{\&epsiv;}(2R_1{d}_x+2R_2{d}_x)}{d_n}$ ①

$C_2=\frac{\mathrm{\&epsiv;}(S_{20}-S2)}{d_n}=\frac{\mathrm{\&epsiv;}({\mathrm{\&pi;r}}_1^2-{\mathrm{\&pi;r}}_2^2)}{d_n}-\frac{\mathrm{\&epsiv;}(2r_1{d}_x+2r_2{d}_x)}{d_n}$ ②

Will be provided withObtaining:

$C_1-C_2*\frac{R_1+R_2}{r_1+r_2}=\frac{\mathrm{\&epsiv;}\mathrm{\&pi;}(R_1^2-R_2^2)}{d_n}-\frac{R_1+R_2}{r_1+r_2}*\frac{\mathrm{\&epsiv;}\mathrm{\&pi;}(r_1^2-r_2^2)}{d_n}$

in the above formula $\frac{R_1+R_2}{r_1+r_2}=K,$ Then $d_n=\frac{\mathrm{\&epsiv;}(S_{10}-{\mathrm{KS}}_{20})}{C_1-{\mathrm{KC}}_2}$

According to $d_n=d_0-\mathrm{\&Delta;}d=d_0(1-\frac{F_n}{E\&CenterDot;S_0})$

Therefore, the following steps are carried out: $F_n=\frac{(d_n-d_0)E\&CenterDot;S_0}{d_0}$

will be described in the above₂-②*C₁Obtaining:

$d_x=\frac{C_2{S}_{10}-C_1{S}_{20}}{2C_2(R_1+R_2)-2C_1(r_1+r_2)};$

by $\mathrm{\&gamma;}=\frac{\mathrm{\&tau;}}{G}=\frac{F_{\mathrm{\&tau;}}}{G\&CenterDot;S_0}=\frac{d_x}{d_0}=\frac{C_2{S}_{10}-C_1{S}_{20}}{d_{0}2C_2(R_1+R_2)-d_{0}2C_1(r_1+r_2)},$ So F_τIs composed of

$F_{\mathrm{\&tau;}}=\frac{(C_2{S}_{10}-C_1{S}_{20})\&CenterDot;G\&CenterDot;S_0}{d_{0}2C_2(R_1+R_2)-d_{0}2C_1(r_1+r_2)}$

2.4 determination of the direction of tangential force

2.4.1 strip-shaped capacitor unit group structure and parameter design

To realize tau_xAnd τ_yTangential response does not mutually influence, and a reserved difference delta is reserved at two ends of the length of the driving electrode₀Thus b is_{0 drive}＝b_{0 bottom}+2·δ₀Wherein in b_{0 drive}The length reservation of the two ends should be ensured theoretically ${\mathrm{\&delta;}}_0\&GreaterEqual;d_0\&CenterDot;\frac{{\mathrm{\&tau;}}_{ymax}}{G},$ Calculated value thereof is ${10}^{-5}\&times;\frac{70\&times;{10}^3}{24\&times;{10}^6}2.9\&times;{10}^{-8}m={10}^{-2}um<<1um,$ Therefore, it should be ensured in terms of process b_{0 drive}-b_{0 bottom}Not less than 0.01 mm. Is composed ofRealize tau_xAnd τ_yThe normal capacitance response is not influenced, and the driving electrode and the sensing electrode of each strip-shaped capacitance unit are arranged on the plane and are provided with certain dislocation offset, so that the mutual influence is eliminated through differential motion.

As shown in fig. 6, four dotted line boxes in the figure are taken as the reference of the sensing electrode on the lower plate, and the position of the sensing electrode on the lower PCB substrate is taken as a reference, then the arrangement of the driving electrode on the upper PCB substrate should be taken as the reference of the edge line of the PCB substrate. Each strip-shaped capacitor unit comprises a driving electrode of an upper polar plate and an induction electrode of a lower polar plate, and the width of each strip-shaped capacitor unit is set to be a₀The width of the groove between two strip-shaped capacitor units is a_δThe pitch of each strip-shaped capacitor unit is a₀+a_δ. Thus ensuring tau already when calculating the normal capacitance output response_xAnd τ_yThe normal capacitance response is not affected. The differences between them and the geometric datum line are delta₀(0.1mm) to ensure that the X-direction differential capacitance unit group I and the X-direction differential capacitance unit group III only generate a pair tau_xThe Y-direction differential capacitance unit group II and the Y-direction differential capacitance unit group IV only generate a pair tau_ySetting an initial misalignment offset delta_xoThe value of which should be guaranteedCalculated value and delta thereof₀Similarly, their initial misalignment offsets are all set at δ_xo＝δ_yo0.01mm to ensure that four capacitor units are at tau_xAnd τ_yTwo groups of differential capacitance pairs can be generated under tangential excitation.

In FIG. 9, a pair of capacitors C_LAnd C_RElectrode size a₀、b₀、d₀All are the same, initial misalignment offset δ₀Also the same, the difference being the left capacitor C_LUpper layer delta₀The point of the tip is pointed at + OX, and the capacitor C on the right_RUpper layer delta₀The sharp corners point to-OX. When tau is_xWhen the content is equal to 0, the content,i.e. the capacitance corresponding to the shaded part of the figure. On the basis thereof, e.g. in-F_xProducing delta under excitation_xThe misalignment of (2) causes a capacitance increase and decrease effect as shown in FIG. 10,

$G_L=\frac{{\mathrm{\&epsiv;}}_0\&CenterDot;{\mathrm{\&epsiv;}}_r\&CenterDot;b_0\&CenterDot;(a_0-{\mathrm{\&delta;}}_0\&PlusMinus;{\mathrm{\&delta;}}_x)}{d_0}---\left(10\right)$

in FIG. 10, C_LAnd C_RDifferential capacitor pair_xWill produce + -delta_xAnd. + -. Δ C_τIn response to (2) the response of (c), $\&PlusMinus;{\mathrm{\&delta;}}_x=\&PlusMinus;d_0\frac{{\mathrm{\&tau;}}_x}{G}.$ δ₀should be of a size that ${\mathrm{\&delta;}}_0\&GreaterEqual;\&PlusMinus;{\mathrm{\&delta;}}_{\mathrm{\&tau;}\max }=\frac{{\mathrm{\&tau;}}_{x\max }}{G}\&CenterDot;d_0,$ Desirable delta₀10 μm, whereby equation (8) can be modified

$G_{\mathrm{\&tau;}x}=G_{\mathrm{\&tau;}0}\&PlusMinus;\frac{{\mathrm{\&epsiv;}}_0\&CenterDot;{\mathrm{\&epsiv;}}_r}{{\mathrm{Ga}}_0}{F}_x---\left(11\right)$

In the formula,the initial capacitance when the shear stress is zero, and the formula (11) is the shear stress input-output characteristic, C_τxAnd F_xIs a linear relationship, and the sensitivity thereof

A is shown in formula (11)₀The smaller the sensitivity of the tangential stress response is, the larger the capacitance unit of the present invention is, the more the strip-shaped capacitance unit group composed of a plurality of strip-shaped capacitors is adopted.

2.4.2 tangential stress Direction calculation

C_ITo C_IIAnd C_IIITo C_IVTwo pairs of differential combinations can be realized, such as the signal differential diagram of the cell capacitor pair of FIG. 11, processed by differential techniques, the total response of the differential output

$O_{\mathrm{\&tau;}x}=\frac{2{\mathrm{mK\&epsiv;}}_0\&CenterDot;{\mathrm{\&epsiv;}}_r}{a_{0}G}{F}_x$

In which either the normal excitation F_nOr tangential excitation F_yAll are not to O_τEffecting, i.e. automatically cancelling, sigma_nAnd τ_yFor tau_xOr interference of the total output. Because the equivalent and congruent capacitance changes are automatically eliminated in all operations in which the signals contain subtraction. And F_yAnd F_xTo sigma_nCan pass through the upper electrode at b₀Direction increased geometric length 2 delta₀And (4) eliminating.

In the same way, the method for preparing the composite material, $O_{\mathrm{\&tau;}y}=\frac{2{\mathrm{mK\&epsiv;}}_0\&CenterDot;{\mathrm{\&epsiv;}}_r}{a_{0}G}{F}_y;$

according to O_τxAnd O_τyThe value of (c) calculates the direction of the tangential force.

2.4 selection of the principal materials and their characteristic parameters

The cross-sectional view of the parallel plate capacitor structure is similar to a sandwich structure as shown in FIG. 12. As can be seen from fig. 12, 1 is an upper PCB substrate, 2 is a lower PCB substrate, 3 is a driving electrode, 4 is a sensing electrode, and 5 is an elastic medium. Distance d between the plates₀The inner spaces of the upper and lower substrates except for the copper foil electrodes were all PDMS (polydimethylsiloxane) super-elastic insulating media filled by a lost wax casting method, which was 0.1 mm. Its mechanical and physical parameters are Young's modulus E equal to 6.2MPa, shear elastic modulus G equal to 4.1MPa, and relative dielectric constant epsilon of medium polarization_γ2.5. Since E and G of the medium are much smaller than the elastic modulus E of copper_{Copper (Cu)}The deformation of the internal dielectric of the capacitor in a stress state is far larger than that of the polar plate because the internal dielectric of the capacitor is 103 GPa.

2.5 electrode lead design

Both the driving electrodes and the sensing electrodes need to be provided with lead-out lines, and considering that the respective driving electrodes are grounded in signal level, the driving electrodes need only share the same lead-out line. The drive electrodes of the circular capacitor unit group and the strip capacitor unit group are connected with the control unit through an outgoing lineEach ring independent lead of the ring capacitor unit group is connected with the control unit, the control unit calculates according to the output value of each ring in a free combination mode, then the average is carried out to obtain the magnitude of the tangential force and the magnitude of the normal force, under the condition that the precision requirement is not high, the ring capacitor unit group can only select two optimal rings to lead out 2 leads, and d is obtained through the two rings_xAnd d_nSo as to obtain the magnitude of the tangential force and the magnitude of the normal force; the X-direction differential capacitance unit group and the Y-direction differential capacitance unit group are respectively led out through an outgoing line to be connected with the control unit and used for calculating the direction of the tangential force. An intermediate converter is arranged between the control unit and the capacitor unit and is used for setting the transmission coefficient of voltage or frequency to the capacitor. The entire capacitor assembly has at least 7 pins leading out from the side of the planar package so that the top and bottom outer surfaces of the entire assembly can be conveniently contacted with the measurement object.

The utility model discloses under the support of new material and new technology, accomplished the design of a novel three-dimensional force sensitive capacitor combination. At 10X 10mm²The stress surface can transmit the stress to the medium more uniformly in the normal direction or the tangential direction. In the contact of space force and sensor surface, the external force is only 1, and the normal direction F can be obtained by summing the capacitances_nInformation of (2), i.e. the whole electrode plate is aimed at F_nMake a contribution to obtain F_xAnd F_yThe three-dimensional force can be completely described, and the normal sensitivity, the tangential sensitivity and the maximum linear error of one-time conversion can be improved according to design parameters.

The present invention has been described above with reference to the accompanying drawings, and it is obvious that the present invention is not limited by the above-mentioned manner, and various insubstantial improvements can be made without modification to the method and technical solution of the present invention, or the present invention can be directly applied to other occasions without modification, all within the scope of the present invention. The protection scope of the present invention shall be subject to the protection scope defined by the claims.

Claims (7)

1. An induction type touch screen is characterized by comprising a touch layer with a top surface and a bottom surface, a pressure sensor array and a touch sensing sensor which are connected to the bottom surface of the touch layer, a control unit respectively connected with the pressure sensor array and the touch sensing sensor, and a touch screen shell consisting of a substrate and a periphery, wherein the touch layer is arranged in the touch screen shell, the touch layer and the periphery are directly provided with a buffer layer consisting of an elastic material, the control unit comprises a touch behavior control unit, a position acquisition control unit and a main control unit respectively connected with the touch behavior control unit and the position acquisition control unit, the position acquisition control unit is used for acquiring touch points and touch positions, the touch behavior unit detects whether the touch screen has touch behaviors, the pressure sensor comprises a control unit, a circular capacitor unit group and a strip capacitor unit group respectively connected with the control unit, the annular capacitor unit group is used for measuring the tangential force and the normal force, the strip-shaped capacitor unit group is used for measuring the direction of the tangential force, and the strip-shaped capacitor unit group is arranged at four corners of the outer substrate of the annular capacitor unit group.

2. The inductive touch screen of claim 1, wherein the touch sensor comprises an X-direction differential capacitance unit combination and a Y-direction differential capacitance unit combination, and is disposed at an end corner of the touch screen, and the touch behavior control unit, and the touch sensor has a higher sensitivity than the pressure sensor array.

3. The inductive touch screen of claim 1, wherein the circular capacitor unit set comprises two or more circular capacitor unit pairs, each circular capacitor unit pair comprises two circular capacitor units, each strip-shaped capacitor unit set comprises an X-direction differential capacitor unit set and a Y-direction differential capacitor unit set, each of the X-direction differential capacitor unit set and the Y-direction differential capacitor unit set comprises two or more capacitor unit modules forming a differential, each capacitor unit module is a comb-shaped structure composed of two or more strip-shaped capacitor units, and each circular capacitor unit and each strip-shaped capacitor unit comprises a driving electrode of an upper plate and a sensing electrode of a lower plate.

4. The inductive touch screen of claim 3, wherein the sensing electrodes and the driving electrodes of each circular ring capacitor unit are opposite and have the same shape, the driving electrodes and the sensing electrodes of each strip capacitor unit have the same width, the length of the driving electrodes of the strip capacitor units is greater than that of the sensing electrodes, and the length of the driving electrodes of the strip capacitor units is twoThe ends are respectively reserved with a left difference delta_{Left side of}And the right difference position delta_{Right side}，b_{0 drive}＝b_{Feeling of 0}+δ_{Right side}+δ_{Left side of}Wherein b is_{0 drive}Length of the driving electrode of the strip-shaped capacitor unit, b_{Feeling of 0}Is the length of the induction electrode of the strip-shaped capacitor unit, and the left difference position delta of the strip-shaped capacitor unit_{Left side of}Right difference delta_{Right side}And is andwherein d is₀Is the thickness of the elastic medium, G is the shear modulus, τ, of the elastic medium_maxThe maximum stress value.

5. The inductive touch screen of claim 3, wherein the set of circular ring capacitive units comprises n concentric circular ring capacitive units, whereina_{Flat plate}Length of parallel plate, r_{Round (T-shaped)}Is the width of the ring capacitor unit, a_{Delta circle}And the electrode distance between two adjacent circular capacitor units.

6. The inductive touch screen of claim 5, wherein the concentric ring capacitive units have a width r_{Round (T-shaped)}And the width a of the strip-shaped capacitor unit₀Equal; electrode spacing a of strip-shaped capacitor unit_{Delta bar}And the electrode spacing a of the circular ring capacitor unit_{Delta circle}Equal, width of the strip-shaped capacitor unitWherein d is₀E is the Young's modulus of the elastic medium, and G is the shear modulus of the elastic medium.

7. The inductive touch screen of claim 3, wherein: a supporting layer is arranged between the touch screen shell substrate and the touch position pressure sensor and the touch behavior pressure sensor, and the supporting layer is made of materials with shock absorption characteristics.