A method for measuring the vertical stiffness of a tire under cornering conditions

Abstract

The application discloses a kind of measurement methods of tire lateral inclination working condition vertical stiffness, including the parameter setting of vertical stiffness test in tire static stiffness testing machine, the parameters include tire pressure, vertical load and displacement loading speed;When tire lateral inclination angle γ is 0, tire vertical stiffness test is carried out, and the radial force F r of tire is collected during measurement test process and the relationship curve of with subsidence amount ρ, and the radial force F r Of tire is collected during measurement test process and the relationship curve of with subsidence amount ρ;When tire lateral inclination angle γ is not 0, tire vertical stiffness test is carried out, and the test data of different lateral inclination angle during measurement test process are collected, and the test data include radial force F r , lateral force F s And subsidence amount ρ;According to the test data obtained in step S3, the tire model formula constructed is input, and the tire vertical stiffness under each lateral inclination angle is calculated.The application designs tire model, deduces tire vertical stiffness under lateral inclination working condition, to realize accurate measurement of tire vertical stiffness under lateral inclination working condition.

Description

Technical Field

[0001] This invention relates to the field of tire testing technology, and in particular to a method for measuring the vertical stiffness of a tire under roll conditions. Background Technology

[0002] The vertical stiffness (also known as radial stiffness) of a tire is one of its fundamental mechanical properties, significantly impacting a vehicle's load-bearing capacity, ride comfort, and handling stability. According to GB / T12549-2013, "Terminology and Definitions for Automobile Handling Stability," the vertical stiffness of a tire refers to the change in vertical load on the tire corresponding to a unit displacement of the wheel center relative to the tire's contact patch plane. When a vehicle is traveling in a straight line, the wheel's center plane is approximately perpendicular to the road surface. In this case, the tire's vertical displacement is the reduction in its section height, which GB / T6326-2014, "Tire Terminology and Definitions," defines as tire deflection.

[0003] When a vehicle turns, due to lateral forces, the tire will roll at a certain angle relative to the contact patch. At this time, the tire's vertical displacement is no longer equivalent to its sinking. Therefore, it is necessary to establish a method for measuring and characterizing the tire's vertical stiffness under roll conditions. Currently, mainstream tire static stiffness testing machines in the industry do not have a device for measuring tire roll when measuring vertical stiffness; they can only perform vertical loading and cannot realize the tire's roll relative to the contact patch. Therefore, they cannot measure the tire's vertical stiffness under roll conditions.

[0004] Due to the influence of vehicle steering characteristics, tires always exhibit a certain degree of body roll relative to the road surface. Experimental studies have shown that, when the vertical load on the tire is the same, the vertical displacement of the wheel center relative to the contact patch increases with the increase of the tire roll angle. This indicates that the vertical stiffness of the tire decreases as the tire roll angle increases. However, existing methods for testing the vertical stiffness of tire static stiffness only measure the tire's vertical stiffness when the roll angle is 0.

[0005] The shortcoming of existing technology is that current mainstream tire static stiffness testing machines in the industry lack a device for measuring tire roll when measuring vertical stiffness; they can only perform vertical loading and cannot achieve tire roll relative to the contact patch. Therefore, they cannot measure tire vertical stiffness under roll conditions. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art. To achieve the above objective, a method for measuring the vertical stiffness of a tire under roll conditions is adopted to solve the problems mentioned in the background art.

[0007] A method for measuring the vertical stiffness of a tire under roll conditions, comprising the following steps:

[0008] Step S1: Setting parameters for the vertical stiffness test on the tire static stiffness testing machine, including tire pressure, vertical load, and displacement loading speed;

[0009] Step S2: When the tire camber angle γ is 0, conduct a tire vertical stiffness test and collect and measure the tire radial force F during the test. r The subsidence ρ is used to obtain the radial force F. r The curve showing the relationship between the amount of sinking ρ and the depth of sinking.

[0010] Step S3: When the tire roll angle γ is not 0, perform a tire vertical stiffness test and collect test data at different roll angles during the test. The test data includes radial force F. r lateral force F s And the amount of sinking ρ;

[0011] Step S4: Input the experimental data obtained in step S3 into the constructed tire model formula, and calculate the tire vertical stiffness at each camber angle.

[0012] As a further aspect of the present invention, the specific steps of step S1 include:

[0013] Parameter settings for vertical stiffness testing on a tire static stiffness testing machine;

[0014] The tire was placed on a static stiffness testing machine, and the tire pressure, vertical load, and displacement loading speed were set simultaneously.

[0015] The tire reaches a quasi-steady state by controlling the displacement loading speed, wherein the displacement loading speed is used to load up to 150% of the tire load index.

[0016] As a further aspect of the present invention, step S3 specifically includes the following steps:

[0017] When the tire roll angle γ is not 0, a tire vertical stiffness test is conducted. A platform with roll angle and high friction coefficient is set on the test bench to conduct the test and obtain test data.

[0018] When the roll angle γ = +α° or γ = -α°, experimental measurements are performed to obtain test data. The average of the two test data is then taken to obtain the tire vertical stiffness test data for the roll angle α°. The test data includes the radial force F. r lateral force F s And the amount of sinking ρ.

[0019] As a further aspect of the present invention, step S4 specifically includes the following steps:

[0020] Step S41: Based on the radial force F in step S2 rBy linearly fitting the curve relating the slope to the subsidence ρ, the radial stiffness k when the roll angle is 0 is obtained. r ;

[0021] Step S42: Substitute the test data from step S3 into the tire model to obtain the vertical force F. z The value of is calculated using the following formula:

[0022] F z =F r cosγ-F s sinγ;

[0023] And to calculate the displacement perpendicular to the road surface, the formula is:

[0024] Δz = ρcosγ;

[0025] Step S43: Based on the obtained vertical force F z The relationship curve between the vertical stiffness k and the displacement Δz is used to obtain the vertical stiffness k with a tilt angle of γ°. z The calculation formula is:

[0026]

[0027] Where γ is the roll angle and λ is the influence coefficient of the roll angle corresponding to the tire loading radius.

[0028] Compared with the prior art, the present invention has the following technical advantages:

[0029] By employing the above technical solution, and using a tire static stiffness testing machine to conduct vertical stiffness tests, a tire model for the vertical stiffness of the tire under roll conditions is derived using a two-way spring model of the tire. This enables accurate measurement of the tire's vertical stiffness under roll conditions using existing tire static stiffness testing machines. This overcomes the current inability to test the vertical stiffness of tires under roll conditions, and the method of this invention is relatively reliable and has high predictive ability, making it of significant application value in research on vehicle comfort, handling stability, and rollover conditions. Attached Figure Description

[0030] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings:

[0031] Figure 1 This is a schematic diagram illustrating the steps of the measurement method according to an embodiment of this application;

[0032] Figure 2 This is a simplified model structural diagram of a tire according to an embodiment of this application;

[0033] Figure 3 This is a schematic diagram of radial loading force on a stiffness testing machine under tilting conditions, according to an embodiment of this application.

[0034] Figure 4 This is a simplified force diagram of a tire model according to an embodiment of this application;

[0035] Figure 5 This diagram illustrates the relationship between the effective roll angle and the nominal roll angle of a tire under lateral loading conditions, as shown in the embodiments disclosed in this application. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Please refer to Figure 1 In this embodiment of the invention, a method for measuring the vertical stiffness of a tire under roll conditions includes the following steps:

[0038] Step S1: Setting parameters for the vertical stiffness test on the tire static stiffness testing machine. These parameters include tire pressure, vertical load, and displacement loading speed. Specific steps include:

[0039] Parameter settings for vertical stiffness testing on a tire static stiffness testing machine;

[0040] The tire was placed on a static stiffness testing machine, and the tire pressure, vertical load, and displacement loading speed were set simultaneously.

[0041] The tire reaches a quasi-steady state by controlling the displacement loading speed, wherein the displacement loading speed is used to load up to 150% of the tire load index.

[0042] In this embodiment, it is specifically based on a two-way spring model of a tire, such as... Figure 2 As shown, the diagram illustrates a simplified tire model. A represents the rim, and B represents the tire's deformable spring. The two-way spring model treats the rim as a rigid body and simplifies the tire into a spring that can deform radially and laterally, with no slippage between the tire and the road surface after the tire tilts.

[0043] Step S2: When the tire camber angle γ is 0, conduct a tire vertical stiffness test and collect and measure the tire radial force F during the test. r The subsidence ρ is used to obtain the radial force F. r The curve showing the relationship between the amount of sinking ρ and the depth of sinking.

[0044] Step S3: When the tire roll angle γ is not 0, perform a tire vertical stiffness test and collect test data at different roll angles during the test. The test data includes radial force F.r lateral force F s And the subsidence ρ, the specific steps include:

[0045] When the tire roll angle γ is not 0, a tire vertical stiffness test is conducted. A platform with roll angle and high friction coefficient is set on the test bench to conduct the test and obtain test data.

[0046] When the roll angle γ = +α° or γ = -α°, experimental measurements are performed to obtain test data. The average of the two test data is then taken to obtain the tire vertical stiffness test data for the roll angle α°. The test data includes the radial force F. r lateral force F s And the amount of sinking ρ.

[0047] Step S4: Input the experimental data obtained in step S3 into the constructed tire model formula to calculate the tire vertical stiffness at each camber angle. Specific steps include:

[0048] Step S41: Based on the radial force F in step S2 r By linearly fitting the curve relating the slope to the subsidence ρ, the radial stiffness k when the roll angle is 0 is obtained. r ;

[0049] Step S42: Substitute the test data from step S3 into the tire model to obtain the vertical force F. z The value of is calculated using the following formula:

[0050] F z =F r cosγ-F s sinγ;

[0051] And to calculate the displacement perpendicular to the road surface, the formula is:

[0052] Δz = ρcosγ;

[0053] Step S43: Based on the obtained vertical force F z The relationship curve between the vertical stiffness k and the displacement Δz is used to obtain the vertical stiffness k with a tilt angle of γ°. z The calculation formula is:

[0054]

[0055] Where γ is the roll angle and λ is the influence coefficient of the roll angle corresponding to the tire loading radius.

[0056] like Figure 3 The diagram shows a tire static stiffness test performed under roll conditions using a tire static stiffness testing machine. The roll angle of the platform is γ, and the radial force F is measured. r and lateral force F sThe vertical stiffness k of the tire z It can be represented as:

[0057]

[0058] Under roll conditions, the tire coordinate system rotates, which affects the radial force F. r and lateral force F s Projecting the force F into the direction perpendicular to the table surface (i.e., the Z direction), we can obtain the vertical force F. z Value:

[0059] F z =F r cosγ-F s sinγ (2)

[0060] In the specific implementation method, the derivation process of the model formula is explained:

[0061] like Figure 4 As shown, the diagram illustrates the forces acting on a simplified tire model. Its radial force can be expressed as:

[0062] F r =k r ρ (3)

[0063] Then the vertical force F z It can be represented as:

[0064] F z =F r cosγ=k r ρcosγ=-k r R z (4)

[0065] From formulas (1) and (4), we can obtain:

[0066]

[0067] From formula (5), it can be seen that when the tire tilts, its vertical stiffness k z Equal to its radial stiffness k r However, actual experimental data shows that the vertical stiffness k during tilting... z Less than its radial stiffness k r This is because during lateral tilt, the effective lateral tilt angle γ of the tire... e It is not equal to the applied nominal roll angle γ.

[0068] like Figure 5 The diagram illustrates the relationship between the effective roll angle and the nominal roll angle when a tire is loaded under roll conditions. The angle between the rim center plane and the Z-axis is the nominal roll angle γ, and the angle between the line connecting the intersection of the tire tread and the Z-axis and the rim center and the Z-axis is the effective roll angle γ. eWhen a tire is under lateral load, its contact patch is nominally considered to be at the center of the tire tread. However, in reality, the contact patch remains on the road surface, and its projection on the tire tread undergoes a lateral shift. This shift is ρsinγ, which is the effective roll angle γ. e The reason for the difference between the nominal roll angle γ and the actual roll angle γ.

[0069] Since γ is relatively small, the offset can be simplified to ργ. Therefore, the effective roll angle γ... e The change in the effective roll angle γ is linearly related to the change in subsidence. Therefore, the effective roll angle γ e It can be represented as:

[0070] γ e =γ(1+λ·dR) L (6)

[0071] Where λ is the influence coefficient of the loading radius on the effective roll angle, R L The loading radius is the straight-line distance from the wheel center to the contact patch center. According to existing technical standards, the tire contact patch center is the intersection of the line of intersection between the wheel center plane and the ground and the projection of the wheel rotation center line onto the ground.

[0072] dR L The change in the loading radius can be expressed as:

[0073]

[0074] Among them, R ref Used as a reference loading radius.

[0075] The vertical component of the loading radius can be expressed as:

[0076] R z =R L ·cosγ (8)

[0077] Then we have:

[0078]

[0079] Expanding cosγ using Taylor series and retaining only the quadratic terms, we get:

[0080]

[0081] Using the effective roll angle to represent the vertical force, we get:

[0082] F z =k r (R0-R L cosγ e (11)

[0083] Substituting formula (6) into formula (11), we get:

[0084] F z =k r R0-k r R L cos[γ(1+λ·dR L (12)

[0085] Substituting formula (7) into formula (12), we get:

[0086]

[0087] Will Performing a Taylor expansion, retaining only the quadratic terms, we get:

[0088]

[0089] Formula (14) is the vertical force F z Regarding the loading radius R L The derivative of the function is:

[0090]

[0091] Due to the loading radius R L With reference loading radius R ref If they are relatively close, then Substituting into formula (15), we get:

[0092]

[0093] The vertical stiffness under tilting conditions can be expressed as:

[0094]

[0095] Substituting formulas (10) and (16) into formula (17), we get:

[0096]

[0097] Formula (18) is the formula for the vertical stiffness model of the tire under the roll condition.

[0098] Since the tire six-component force testing equipment can measure the vertical stiffness at various roll angles, the reliability of the model can be verified by the test data obtained on this equipment under roll conditions.

[0099] Test data of a specific tire model under roll conditions on a six-component force testing apparatus were selected as a case study. The test yielded the corresponding loading radius R at each roll angle γ. L and vertical force F zThe vertical force F of the model can be calculated using the vertical stiffness model formula under the tilting condition of this patent. z_cal The vertical force F obtained from the test z The calculated vertical force F z_cal When the error ε between them is minimized, the identification parameters in the model can be obtained.

[0100] The least squares method is used to define the error:

[0101]

[0102] To make the radial force F r The fitting is more accurate, and a quadratic polynomial is used to express the radial force F. r The relationship between the amount of sedimentation ρ and the sedimentation is expressed as follows:

[0103] F r =k r1 ρ+k r2 ρ 2 (20)

[0104] Where, k r1 and k r2 These are the coefficients of the linear term and the quadratic term, respectively.

[0105] By identifying the data when the roll angle γ = 0°, the radial stiffness coefficient k can be obtained. r1 and k r2 By identifying data at a roll angle γ = ±6°, the influence coefficient λ of the parameter loading radius on the effective roll angle and the reference loading radius R can be obtained. ref The relevant identification parameters and errors are shown in Table 1 below:

[0106] Table 1

[0107] Parameters and Errors numerical values <![CDATA[k r1 ]]> 229.04 N / mm <![CDATA[k r2 ]]> <![CDATA[1.264N / mm 2 ]]> λ 7.44 <![CDATA[R ref ]]> 335.29mm ε(γ=0°) 0.09％ ε(γ=+6°) 0.04％ ε (whole) 0.77％

[0108] The loading radius R corresponding to each tilt angle γ L and vertical force F z The vertical stiffness k of the test can be directly linearly fitted. z Using the model formula of this patent and the identification parameters in Table 1, the vertical stiffness k calculated by the model can be obtained. z_cal The relevant data is shown in Table 2 below:

[0109] Table 2

[0110] γ(°) <![CDATA[k z (N / mm)]]> <![CDATA[k z_cal (N / mm)]]> -8 231.63 223.50 -6 241.33 241.41 -4 251.92 254.20 -2 260.61 261.87 -1 264.32 263.79 0 264.43 264.43 1 264.70 263.79 2 261.68 261.87 4 254.27 254.20 6 244.42 241.41 8 235.47 223.50

[0111] Table 2 shows that the vertical stiffness error calculated using the test method of this patent is 1.80%. It also shows that the larger the roll angle γ, the greater the decrease in vertical stiffness compared to the case without a roll angle. When γ = ±8°, the vertical stiffness decreases by 15.48%. Therefore, the influence of the roll angle on the vertical stiffness cannot be ignored.

[0112] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention. The scope of the invention is defined by the appended claims and their equivalents, all of which should be included within the scope of protection of the invention.

Claims

1. A method for measuring the vertical stiffness of a tire under roll conditions, characterized in that, The specific steps include: Step S1: Setting parameters for the vertical stiffness test on the tire static stiffness testing machine, including tire pressure, vertical load, and displacement loading speed; Step S2, when the tire camber angle A tire vertical stiffness test was conducted when the value was 0, and the tire radial force was collected and measured during the test. With sinking amount And obtain radial force With sinking amount Relationship curve; Step S3, when the tire camber angle When the value is not zero, a tire vertical stiffness test is conducted, and test data at different roll angles are collected and measured during the test. The test data includes radial force. lateral force and sinking amount ; Step S4: Based on the test data obtained in step S3, input the constructed tire model formula to calculate the tire vertical stiffness at each camber angle. The specific steps include: Step S41: Based on the radial force in step S2 With sinking amount Linear fitting was performed on the relationship curve to obtain the radial stiffness when the roll angle was 0. ; Step S42: Substitute the test data from step S3 into the tire model to obtain the vertical force. The value of is calculated using the following formula: ； And to calculate the displacement perpendicular to the road surface, the formula is: ； Step S43: Based on the obtained vertical force and displacement The relationship curve is used to obtain the roll angle. vertical stiffness The calculation formula is: ； in, The roll angle is... This is the influence coefficient of the roll angle corresponding to the tire loading radius.

2. The method for measuring the vertical stiffness of a tire under roll conditions according to claim 1, characterized in that, The specific steps of step S1 include: Parameter settings for vertical stiffness testing on a tire static stiffness testing machine; The tire was placed on a static stiffness testing machine, and the tire pressure, vertical load, and displacement loading speed were set simultaneously. The tire reaches a quasi-steady state by controlling the displacement loading speed, wherein the displacement loading speed is used to load up to 150% of the tire load index.

3. The method for measuring the vertical stiffness of a tire under roll conditions according to claim 1, characterized in that, The specific steps of step S3 include: When the tire camber angle When the value is not 0, a tire vertical stiffness test is conducted. The test data is obtained by setting up a platform with an inclination angle and a high coefficient of friction on the test bench. When the roll angle or At that time, experimental measurements were conducted to obtain experimental data, and the average of the two experimental data was taken to obtain the roll angle. The tire vertical stiffness test data, including radial force. lateral force and sinking amount .

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