CN204788986U - Tire homogeneity parameter measurement device - Google Patents

Abstract

The utility model relates to a tire homogeneity parameter measurement device, including the load wheel, sensor and sensing system signal processor, the load wheel is close to the tire as the driven camber of wheels of tire, the upper and lower both ends at the load wheel are established as the both ends strong point of load wheel to the sensor, radial force between sensor collection load wheel and the testing tire and yawing force erupt simultaneously and give sensing system signal processor, the sensor includes that ring electricity n holds unique tuple and strip electric capacity unique tuple, 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, the utility model discloses a tire homogeneity detection device measures radial force and yawing force between tire and the load round, through these two parameter analysis radial force fluctuations, yawing force fluctuation, tapering, off tracking, radial missing (top, central authorities, bottom), lateral deviation (top, bottom) isoparametric, scientifically calibrates the inhomogeneities of tire.

Description

Tire uniformity parameter measuring device

Technical Field

The invention belongs to the technical field of automobile equipment detection, and particularly relates to a tire uniformity parameter measuring device.

Background

Tire uniformity refers to the lack of uniformity in the circumferential force fluctuation characteristics of a tire under radial load and high speed rotation. According to the mechanics principle and the mechanical movement principle, under the condition that an automobile tire runs and rotates at a high speed, the tire generates alternating and fluctuating radial force and lateral force due to uneven organization of internal materials, uneven size and appearance, errors in assembly size and the like, so that the vertical vibration, the left and right deviation, noise and the like of the automobile are caused, and the maneuverability, the comfort degree or the stability of the automobile are influenced. The automobile parts can be seriously damaged, and even traffic accidents can be caused.

The radial force and the lateral force obtained by the tire uniformity detection device are measured, parameters such as radial force fluctuation, lateral force fluctuation, taper, deviation, radial deviation (top, center and bottom), lateral deviation (top and bottom) and the like are analyzed through the two parameters, the tire nonuniformity is scientifically calibrated, the tire nonuniformity is corrected, the tire nonuniformity reaches the minimum value, and therefore the purpose of improving and improving the tire quality is achieved.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a tire uniformity parameter measuring device, wherein a sensor is arranged at the upper end point and the lower end point of a load wheel, the lateral force and the radial force of a tire on the load wheel are measured, and the uniformity of the tire is analyzed by analyzing parameters such as the taper effect, the angle effect, the radial force fluctuation and the lateral force fluctuation of the radial force and the lateral force.

The technical scheme of the invention is as follows: a tire uniformity parameter measuring device comprises a load wheel, a sensor and a sensing system signal processor, wherein the load wheel is used as a driven wheel curved surface of a tire and is close to the tire, the sensor is used as two-end supporting points of the load wheel and is arranged at the upper end and the lower end of the load wheel, the sensor collects radial force and lateral force between the load wheel and a test tire and sends the radial force and the lateral force to the sensing system signal processor, the sensor comprises a ring capacitor unit group and a strip capacitor unit group, the strip capacitor unit group is arranged at the four corners of an outer substrate of the ring capacitor unit group, the ring capacitor unit group comprises more than two pairs of ring capacitor unit pairs, each ring capacitor unit pair comprises two ring capacitor units, each strip capacitor unit group comprises an X-direction differential capacitor unit group and a Y-direction differential capacitor unit group, and each of the X-direction differential capacitor unit group and the Y-direction differential capacitor unit group comprises, the capacitor unit module is of a comb-tooth-shaped structure consisting of more than two strip-shaped capacitor units, and each ring-shaped capacitor unit and each strip-shaped capacitor unit respectively comprise a driving electrode of an upper polar plate and an induction electrode of a lower polar plate.

The tire uniformity detection device further comprises a main shaft, an upper rim and a lower rim, wherein the upper rim and the lower rim are overlapped with the axis of the main shaft, the lower rim is integrated with the main shaft, the upper rim can freely move up and down, the axis of the load wheel is parallel to the axis of the main shaft, and the tire is clamped between the upper rim and the lower rim. 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}The length of the induction electrode of the strip-shaped capacitance unit. 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 driving electrodes and the sensing electrodes of the strip-shaped capacitor units of the two groups of capacitor unit modules which mutually form the differential are provided with initial dislocation offsets along the width direction, and the dislocation offsets have the same size and opposite directions. 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 capacitors. The X-direction differential capacitance unit group and the Y-direction differential capacitance unit group both comprise m strip-shaped capacitance units,wherein, a_{Flat plate}Length of parallel plate, a_{Delta bar}Is the electrode spacing between two adjacent strip-shaped capacitor units, a₀The width of the strip-shaped capacitor unit. 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. The drive electrodes of the ring capacitor unit group and the strip capacitor unit group are connected with the sensing system signal processor through an outgoing line, the induction electrode of each ring capacitor unit of the ring capacitor unit group is connected with the sensing system signal processor through an independent lead, and the induction electrodes of the capacitor unit modules of the X-direction differential capacitor unit group and the Y-direction differential capacitor unit group are connected with the sensing system signal processor through an outgoing line respectively. Intermediate converters are respectively arranged among the ring capacitor units, the capacitor unit modules and the sensing system signal processor and are used for setting transmission coefficients of voltage to capacitance or frequency to capacitance.

The invention has the following positive effects: the tire uniformity detection device measures the radial force and the lateral force between a driving wheel tire and a driven wheel load wheel, analyzes parameters such as radial force fluctuation, lateral force fluctuation, taper, deviation, radial deviation (top, center and bottom), lateral deviation (top and bottom) and the like through the two parameters, scientifically calibrates the tire nonuniformity, guides the tire nonuniformity correction, enables the tire nonuniformity to reach the minimum value, and achieves the purposes of improving and improving the tire quality. In addition, the two-dimensional force sensor can measure normal force and tangential force simultaneously, has high sensitivity and high utilization efficiency of the polar plate, contributes to the normal force by the whole circular capacitor unit group, and has better dynamic performance.

Drawings

FIG. 1 is a diagram of an area analysis of concentric ring offset misalignment according to an embodiment of the present invention.

FIG. 2 is a graph of outer concentric ring misalignment versus outer diameter circle analysis for an embodiment of the present invention.

FIG. 3 is a plan layout view of a parallel plate capacitor according to an embodiment of the present invention.

Fig. 4 is a structural diagram of a driving electrode according to an embodiment of the present invention.

Fig. 5 is a rectangular coordinate system of a flat capacitor plate according to an embodiment of the present invention.

Fig. 6 is a diagram of two sets of circular capacitor sets according to an embodiment of the present invention.

FIG. 7 is an initial misalignment map of a differential stripe capacitor cell according to an embodiment of the present invention.

FIG. 8 is a graph illustrating the offset of the differential strip capacitor unit after being stressed according to the embodiment of the present invention.

FIG. 9 is a signal differential schematic of a cell capacitor pair according to an embodiment of the present invention.

Fig. 10 is a structural view of a tire uniformity testing apparatus according to an embodiment of the present invention.

FIG. 11 is a tire uniformity test force analysis diagram in accordance with an embodiment of the present invention.

The device comprises a main shaft 1, a lower rim 2, an upper rim 3, a tire 4, a load wheel 5 and a sensor 6.

Detailed Description

The following description of the embodiments with reference to the drawings is provided to describe the embodiments of the present invention, and the embodiments of the present invention, such as the shapes and configurations of the components, the mutual positions and connection relationships of the components, the functions and working principles of the components, the manufacturing processes and the operation and use methods, etc., will be further described in detail to help those skilled in the art to more completely, accurately and deeply understand the inventive concept and technical solutions of the present invention.

The main ideas of the invention are as follows: the radial tire is formed by laminating, forming and vulcanizing multiple layers of rubber prefabricated materials and composite rubber prefabricated materials with steel cords, so that the nonuniformity of the materials or the nonuniformity caused by mass eccentricity and the like is generated. According to relevant mechanics principles, tires with certain degree of non-uniformity can show a plurality of motion characteristics in the dynamic motion process, such as the characteristics of friction existing in all directions of the tires and the ground, the change of load borne by the tires, the taper effect and the angle effect which cause the tire deformation, and the like.

The coning effect refers to a lateral force excursion that does not change sign as the direction of tire rotation changes. The angular effect refers to a lateral force deflection that changes sign as the direction of tire rotation changes. In order to calculate the conicity effect and the angle effect, the average value of the lateral force of the tire under the condition of forward rotation and reverse rotation, namely the forward rotation lateral force offset and the reverse rotation lateral force offset, must be obtained, and the two indexes are the result of obtaining the intermediate data of the conicity effect and the angle effect and are also used as a measure of uniformity. The analysis of the radial force fluctuation and the lateral force fluctuation of the tire is further specified to the forward rotation condition and the reverse rotation condition, meanwhile, 1-10 harmonics of the radial force fluctuation and the lateral force fluctuation are main components forming the radial force fluctuation and the lateral force fluctuation, and the size (amplitude) of the component occupied by each harmonic also reflects the characteristics of the tire and is also a parameter for uniformity investigation. For each harmonic of radial force fluctuation and lateral force fluctuation, the first harmonic component is more representative, and the amplitude greatly influences the force fluctuation.

The radial force fluctuation refers to the peak-to-peak value (unit: N) of the radial force applied to the tire in one or more rotation periods of forward rotation or reverse rotation; radial force 1-10 subharmonics (RFH 1-RFH 10) means that a relation curve of the radial force of the tire and the tire rotation angle obtained by a force fluctuation test is a resonance curve, the radial force stress waveforms in one or more rotation periods of the forward rotation or the reverse rotation of the tire are decomposed into 1 to 10 subharmonics by Fourier analysis, wherein 1-order component of the fundamental wave is called a first harmonic (RFH1) or a fundamental wave (unit: N); lateral Force Variation (LFV) refers to the peak-to-peak value (in N) of the lateral force exerted by a tire during one or more cycles of forward or reverse rotation; the lateral force 1-10 harmonics (LFH 1-LFH 10) means that a relation curve of the lateral force of the tire and the tire rotation angle obtained by a force fluctuation test is a resonance curve, the lateral force stress waveforms in one or more rotation periods of the forward rotation or the reverse rotation of the tire are decomposed into 1 to 10 harmonics by Fourier analysis, wherein the 1 st component of the fundamental wave is called a first harmonic (RFH1) or a fundamental wave (unit: N); lateral force deflection (LSFT) refers to the average value (in N) of the integral of the lateral force of a tire over one or more cycles of rotation in either forward or reverse rotation.

As shown in fig. 10, which is a schematic structural view of the tire uniformity detecting apparatus of the present invention, the upper and lower rims 2 are aligned with the axis of the spindle 1, the lower rim 2 is integrated with the spindle 1, and the upper rim 3 is vertically movable. The axis of the load wheel 5 is parallel to the axis of the main shaft 1, and the upper rim 3 and the load wheel 5 are far away from the main shaft 1 before testing and are respectively positioned at the respective original positions. During testing, the tire is loaded onto the lower rim 2, the upper rim 3 is lowered, the relative positions of the upper and lower rims are locked and the tire 4 is clamped, the tire 4 is inflated, and the internal pressure of the tire 4 is kept constant. The tire 4 is fixed to the upper and lower rims by the inflation pressure so that the relative misalignment of the tire 4 with the upper and lower rims does not occur during the rotation of the spindle 1. The load wheel 5 is close to and contacts the tire 4 horizontally to the left, constant pressure is applied to the tire 4, the tire 4 and the load wheel 5 rotate at a constant rotating speed through friction force, the relative positions of the spindle 1 and the tire 4 are unchanged, and the spindle 1 and the tire 4 rotate at the same angular speed.

The force applied between the tire 4 and the load wheel 5 is analyzed, including radial force, lateral force and tangential friction force, and since the friction force is the driving force of the load wheel 5, it is not studied here, because the radial force, the axis of the spindle 1, the axis of the load wheel 5, the plane of the force sensor 6 and the center of the contact surface of the tire 4 and the load wheel 5 are all in the same plane, so that a two-dimensional orthogonal force system as shown in the figure is established for force analysis.

The two-dimensional orthogonal force sensors 6 are arranged at two end points of the load wheel 5 in the figure, which are two end supporting points of a central shaft of the load wheel 5, the load wheel 5 applies load to the tire 4, the axes of the load wheel and the tire 4 are parallel, the force applied to the sensors 6 and the tire 4 is shown in figure 11, and the radial force F of the tire 4_rEqual to the sum of the forces in the X direction of the upper and lower load cells 6, i.e. F₃+F₅Lateral force F₁Equal to the sum of the Y-direction forces of the up-down sensor 6, i.e. F₂+F₄。

After a plurality of rotation periods, the load wheel 5 and the tire 4 stop rotating, the tire 4 deflates, the upper rim 3 and the load wheel 5 horizontally return to the reset position, and the sensing system signal processor calculates all the acquired data to obtain all the uniformity indexes of the tested tire, thereby completing the uniformity test.

The sensor comprises a circular ring capacitor unit group and strip capacitor unit groups, wherein the circular ring capacitor unit group is used for measuring the tangential force and the normal force, the strip capacitor unit groups are used for measuring the direction of the tangential force, and the strip capacitor unit groups are arranged at four corners outside the circular ring capacitor unit group of the substrate. The ring capacitor unit group comprises more than two groups of ring capacitor unit pairs, each ring capacitor unit pair comprises two ring capacitor units, each strip-shaped capacitor unit group comprises an X-direction differential capacitor unit group and a Y-direction differential capacitor unit group, and the X-direction differential capacitor unitsThe group and the Y-direction differential capacitor unit group respectively comprise more than two capacitor unit modules which mutually form differential, the capacitor unit modules adopt a comb-shaped structure consisting of more than two strip-shaped capacitor units, and each ring-shaped capacitor unit and each strip-shaped capacitor unit respectively comprise a driving electrode of an upper polar plate and an induction electrode of a lower polar 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}The length of the induction electrode of the strip-shaped capacitance unit. 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 medium, G is the shear modulus, τ, of the elastic medium_ymaxThe maximum stress value. The driving electrodes and the sensing electrodes of the strip-shaped capacitor units of the two groups of capacitor unit modules which mutually form the differential are provided with initial dislocation offsets along the width direction, and the dislocation offsets have the same size and opposite directions. 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_{Flat plate}Length of parallel plate, a_{Delta bar}Is the electrode spacing between two adjacent strip-shaped capacitor units, a₀The width of the strip-shaped capacitor unit. 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. The drive electrodes of the ring capacitor unit group and the strip capacitor unit group are connected with the sensing system signal processor through an outgoing line, the induction electrode independent lead of each ring capacitor unit of the ring capacitor unit group is connected with the sensing system signal processor, and the induction electrodes of the capacitor unit modules of the X-direction differential capacitor unit group and the Y-direction differential capacitor unit group are respectively led out through an outgoing line and connected with the sensing system signal processor. Intermediate converters are respectively arranged among the ring capacitor units, the capacitor unit modules and the sensing system signal processor and are used for setting transmission coefficients of voltage or frequency to the capacitors.

The derivation and principle of the present invention, the shape, structure, mutual position and connection relationship of 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. 1-9.

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 sigma₀Is excited to produce a relative deformation epsilon_n＝δ_n/d₀＝σ_nAnd E, substituting the formula (1) to obtain the input-output characteristics

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

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 size of the patient is,is 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. 1, 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. 2 is an analysis graph of capacitance of outer concentric ring versus outer diameter circle, where the distance between the centers of the two circles 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):

S_{outer cover}＝S_{Fan beta}-S_{Fan alpha}+S_{Diamond shape}

$\begin{array}{c}=\frac{1}{2}{R_1}^2\left(2\mathrm{\&pi;}-2\mathrm{\&alpha;}\right)-\frac{1}{2}{R_1}^2*2\mathrm{\&alpha;}+4*\frac{1}{2}*\frac{d_x}{2}{R}_1\sin \mathrm{\&alpha;}\\ ={{\mathrm{\&pi;R}}_1}^2+2{R_1}^2\mathrm{\&alpha;}+d_x{R}_1\sin \mathrm{\&alpha;}\\ ={{\mathrm{\&pi;R}}_1}^2-2{R_1}^2\arccos \frac{d_x}{2R_1}+d_x{R}_1\sqrt{1-\frac{d_x^2}{4R_1^2}}\end{array}$

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_τThe 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. 2, 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 calculatedThe resulting capacitance is:

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

according to shear Hooke's law

τ_x＝γ_x·G＝G·δ_x/d₀(7)

Substituting (7) into (6) to obtain

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

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

$S_{\mathrm{\&tau;}x}=\frac{{\mathrm{dC}}_{\mathrm{\&tau;}}}{{\mathrm{dF}}_x}=\frac{2{\mathrm{\&epsiv;}}_0\&CenterDot;{\mathrm{\&epsiv;}}_r}{G\mathrm{\&pi;}(R_1-R_2)}---\left(10\right)$

From equation (10), 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. 3 and the block diagram of the drive electrode in FIG. 4, at a 10X 10mm thickness²The circular ring contact type parallel plate three-dimensional pressure sensor comprises a sensing system signal processor, 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 sensing system signal processor, and the circular ring capacitance unit group is used for measuring tangential force and normal directionThe force is large, the direction of the tangential force is measured by the strip-shaped capacitor unit groups, and the strip-shaped capacitor unit groups are arranged at four corners outside the circular capacitor unit groups 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 fig. 5, a rectangular coordinate system of the plate capacitor is shown, where the origin of the coordinate system is at the origin of a concentric circle of the circular capacitor unit group, the X-axis and the Y-axis are along the diagonal direction of the plate 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 located on the positive and negative half axes of the X-axis and are symmetric along the Y-axis, the Y-direction differential capacitor unit group includes a Y-direction differential capacitor unit group ii and a Y-direction differential capacitor unit group iv, the Y-direction differential capacitor unit group ii and the Y-direction differential capacitor unit group iv are located on the positive and negative half axes of the Y-axis and are symmetric along_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-shaped structure and an X squareThe differential capacitance unit group and the Y-direction differential capacitance unit group both comprise m strip-shaped capacitance 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

The circular-ring capacitor unit is placed in a rectangular coordinate system shown in fig. 5, three-dimensional excitation is applied to the outer surface of the capacitor plate, and the generated contact-type acting force has three directional components of Fx, Fy and Fz, the acting directions of Fx and Fy are along the X axis and the Y axis, and the acting direction of Fz is along the OZ axis, namelyThe 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: μm) of the elastic medium, δ x and δ y are the relative dislocation (unit: μm) of the upper and lower electrode plates of the circular ring capacitor unit, and the sign of the displacement 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. 6. 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.

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 theoreticallyCalculated value thereof is ${10}^{-5}\&times;\frac{70\&times;{10}^3}{2.4\&times;{10}^6}=2.9\&times;{10}^{-8}m={10}^{-2}um<<1um,$ Therefore, it should be ensured in terms of process b_{0 drive}－b_{0 bottom}Not less than 0.01 mm. To realize tau_xAnd τ_yThe driving electrode and the inductance of each strip-shaped capacitor unit do not influence the normal capacitance responseThe electrodes are arranged in a planar arrangement with a certain offset, which counteracts the mutual influence by differential.

As shown in fig. 4, 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. 7, 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. shading in the figureThe capacitance corresponding to the part. 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. 8,

$C_L=\frac{{\mathrm{\&epsiv;}}_0\&CenterDot;{\mathrm{\&epsiv;}}_r\&CenterDot;b_0\&CenterDot;(a_0-{\mathrm{\&delta;}}_0\&PlusMinus;{\mathrm{\&delta;}}_x)}{d_0}---\left(13\right)$

in FIG. 8, C_LAnd C_RDifferential capacitor pair_xWill produce + -delta_xAnd. + -. Δ C_τIn response to (2) the response of (c),δ₀should be of a size thatDesirable delta₀By 10 μm, formula (11) can be modified to

$C_{\mathrm{\&tau;}x}=C_{\mathrm{\&tau;}0}\&PlusMinus;\frac{{\mathrm{\&epsiv;}}_0\&CenterDot;{\mathrm{\&epsiv;}}_r}{{\mathrm{Ga}}_0}{F}_x---\left(14\right)$

In the formula,the initial capacitance when the shear stress is zero, and the formula (14) is the shear stress input-output characteristic, C_τxAnd F_xIs a linear relationship, and the sensitivity thereof

A is shown by formula (14)₀The smaller the sensitivity of tangential stress response is, the larger the sensitivity of tangential stress response is, so that the capacitor unit adopts a strip-shaped capacitor unit group consisting of a plurality of strip-shaped capacitors.

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. 9, 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

Plate spacing d of parallel plate capacitor₀The 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 driving electrodes of the ring capacitor unit group and the strip capacitor unit group are connected with a sensing system signal processor through an outgoing line, each ring independent lead of the ring capacitor unit group is connected with the sensing system signal processor, the sensing system signal processor calculates according to the output value free combination of each ring, then averaging is carried out to obtain the size of the tangential force and the size 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 sensing system signal processor and used for calculating the direction of the tangential force. An intermediate converter is arranged between the sensing system signal processor 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 invention completes a new type under the support of new materials and new technologyAnd designing a 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 the sensor surface, the external force is only 1, and the information of the normal Fn can be obtained by summing the capacitance, namely the whole electrode plate contributes to the Fn calculation, and F can be obtained_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 invention has been described above with reference to the accompanying drawings, it is obvious that the invention is not limited to the specific implementation in the above-described manner, and it is within the scope of the invention to apply the inventive concept and solution to other applications without substantial modification.

Claims (10)

1. A tire uniformity parameter measuring device is characterized by comprising a load wheel, a sensor and a sensing system signal processor, wherein the load wheel is used as a driven wheel curved surface of a tire to be close to the tire, the sensor is used as two-end supporting points of the load wheel and is arranged at the upper end and the lower end of the load wheel, the sensor collects radial force and lateral force between the load wheel and the tested tire and sends the radial force and the lateral force to the sensing system signal processor, the sensor comprises a ring capacitor unit group and a strip capacitor unit group, the strip capacitor unit group is arranged at four corners of an outer base plate of the ring capacitor unit group, the ring capacitor unit group comprises more than two pairs of ring capacitor unit pairs, the ring capacitor unit pair comprises two ring capacitor units, the strip capacitor unit group comprises an X-direction differential capacitor unit group and a Y-direction differential capacitor unit group, the X-direction differential capacitor unit group and the Y-direction differential capacitor unit group both comprise more than two, the capacitor unit module is of a comb-tooth-shaped structure consisting of more than two strip-shaped capacitor units, and each ring-shaped capacitor unit and each strip-shaped capacitor unit respectively comprise a driving electrode of an upper polar plate and an induction electrode of a lower polar plate.

2. The apparatus according to claim 1, wherein the detecting device further comprises a main shaft, and upper and lower rims, the upper and lower rims are coincident with an axis of the main shaft, the lower rim is integrated with the main shaft, the upper rim is movable up and down, an axis of the load wheel is parallel to an axis of the main shaft, and the tire is clamped between the upper and lower rims.

3. The tire uniformity parameter measuring device of claim 2, wherein the sensing electrode and the driving electrode of each circular ring capacitor unit are opposite and have the same shape, the driving electrode and the sensing electrode of each strip capacitor unit have the same width, the driving electrode length of the strip capacitor unit is longer than the sensing electrode length, and the left difference δ is reserved at each end of the driving electrode length of the 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}The length of the induction electrode of the strip-shaped capacitance unit.

4. The apparatus as claimed in claim 3, wherein the strip-shaped capacitor unit has a left difference δ_{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 apparatus according to claim 2, wherein the driving electrodes and the sensing electrodes of the two strip-shaped capacitor units forming the differential capacitor unit module are provided with initial offset along the width direction, and the offset is the same and opposite.

6. The tire uniformity parameter measurement device of claim 2, wherein the set of toroidal capacitor cells comprises n concentric toroidal capacitor cells, whereinWherein, 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.

7. The tire uniformity parameter measuring device of claim 2, wherein each of the X-direction differential capacitance unit group and the Y-direction differential capacitance unit group comprises m strip-shaped capacitance units,wherein, a_{Flat plate}Length of parallel plate, a_{Delta bar}Is the electrode spacing between two adjacent strip-shaped capacitor units, a₀The width of the strip-shaped capacitor unit.

8. The tire uniformity parameter measurement device of claim 2, wherein the concentric ring capacitor cells 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.

9. The tire uniformity parameter measuring device of claim 2, wherein the driving electrodes of the circular ring capacitor unit group and the strip capacitor unit group are connected with the sensing system signal processor through a lead wire, the sensing electrode of each circular ring capacitor unit of the circular ring capacitor unit group is individually connected with the sensing system signal processor through a lead wire, and the sensing electrodes of the capacitor unit modules of the X-direction differential capacitor unit group and the Y-direction differential capacitor unit group are respectively connected with the sensing system signal processor through a lead wire.

10. The apparatus according to claim 2, wherein intermediate converters are respectively disposed between the toroidal capacitive unit, the capacitive unit module and the sensing system signal processor, and are configured to set a transmission coefficient of voltage to capacitance or frequency to capacitance.