JP6422162B2 - Tire stiffness evaluation method - Google Patents

Description

  The present invention relates to a tire stiffness evaluation method. Specifically, the present invention relates to a method for evaluating a feeling of rigidity close to human sensitivity.

  Commercial tires are selected from various viewpoints such as performance, design, brand, and price. In commercially available tires, the purchaser may actually touch and evaluate the tire stiffness. For example, a purchaser deforms a tread portion, a sidewall portion, or the like of a tire. A purchaser evaluates a feeling of rigidity from this deformation state and the feeling received at that time.

  This feeling of rigidity is one standard for selecting a tire. This feeling of rigidity is obtained by sensory evaluation. This feeling of rigidity is a subjective evaluation. It is not easy to express this feeling of rigidity quantitatively.

  Japanese Unexamined Patent Application Publication No. 2014-122814 discloses a method for evaluating the tire stiffness. In this method, a load is applied to the tire. A tire deformation amount δ from a state in which the load Fa is applied to a state in which the load Fb is applied is obtained. The spring constant of the tire is calculated from the load change amount dF between the load Fa and the load Fb and the deformation amount δ. This method can quantitatively evaluate the tire stiffness.

JP 2014-122814 A

  According to the stiffness evaluation method disclosed in JP 2014-122814 A, an evaluation result close to sensory evaluation can be obtained. In this evaluation method, the feeling of rigidity is evaluated in a state where low-pressure air is filled. In general, the feeling of rigidity of a commercially available tire is evaluated with a tire that is not filled with air. The evaluation result by this evaluation method does not necessarily coincide with the result of sensory evaluation of a commercially available tire.

  An object of the present invention is to provide a method for evaluating the tire rigidity, which can provide an evaluation result closer to sensory evaluation.

  The tire stiffness evaluation method according to the present invention includes a preparation step in which a tire assembly in which a tire is incorporated in a rim and an air pressure is set to atmospheric pressure is prepared, and a tread surface of the tire assembly is applied to a pressing surface. A measurement process in which the displacement amount and the load load of the tire assembly are measured in contact with each other and an evaluation process in which the rigidity of the tire is evaluated based on the relationship between the displacement amount and the load load are provided. In this evaluation process, when the horizontal axis is the displacement amount and the vertical axis is the load load, the first and second inflection points of the graph of the function of the displacement amount and the load load are obtained. This first inflection point is the first inflection point when the amount of displacement is increased from zero. This second inflection point is the next inflection point after the first inflection point when the displacement amount is increased. The load at the first inflection point is taken as the first index. The inclination in the predetermined range in which the displacement amount is further increased beyond the second inflection point is used as the second index. The rigidity of the tire is evaluated based on the first index and the second index.

Preferably, the pressing surface in the measurement step is a flat surface. The pressing surface is in contact with a tread surface from one tread end in the axial direction of the tire to the other tread end. Preferably, the area obtained by integrating the length in the front-rear direction of the pressing surface and the tread width from one tread end to the other tread end is 25 cm ² or more and 100 cm ² or less.

  Preferably, in the measurement step, the maximum value of the load is 0.45 kN or more and 0.7 kN or less.

  Preferably, the inclination of the predetermined range in the evaluation step is an inclination of a range in which the amount of displacement from the second inflection point is 5 mm or more and 25 mm or less.

  Preferably, when the first index is equal to or greater than a predetermined first reference value and the second index is equal to or greater than a predetermined second reference value, the tire stiffness is evaluated as good.

  In the tire stiffness evaluation method according to the present invention, a first inflection point and a second inflection point are required. The load applied at the first inflection point and the inclination in a predetermined range in which the displacement is further increased beyond the second inflection point are used as evaluation indexes. This evaluation of rigidity gives an evaluation result closer to human sensory evaluation than conventional evaluation methods of rigidity.

FIG. 1 is an explanatory view showing a side view of a method of evaluating a tire stiffness feeling according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing a front view of a method for evaluating a tire stiffness feeling according to an embodiment of the present invention. FIG. 3 is a graph showing a function of the amount of displacement and the applied load according to the tire stiffness evaluation method of FIG. FIG. 4 is an explanatory diagram showing a first index and a second index by the tire stiffness evaluation method of FIG.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  1 and 2 show a tire assembly 2 and a testing machine 4 for evaluating the feeling of rigidity. The tire assembly 2 is attached to a testing machine 4. In the following description, unless otherwise specified, the left-right direction in FIG. 1 is the axial direction of the tire assembly 2, the direction perpendicular to the paper surface is the circumferential direction of the tire assembly 2, and the front-back direction of the testing machine 4. . In this description, the vertical direction is described as the vertical direction in FIG. As shown in FIG. 2, the tire assembly 2 includes a tire 6 and a rim 8. The rim 8 is a regular rim of the tire 6.

  The testing machine 4 includes a gantry 10, a support body 12, and a pressing tool 14. A support 12 is attached to the upper part 10 a of the gantry 10. The gantry 10 includes a support column 10a and a test table 10b. The lower end of the column 10a is fixed to the test table 10b. The support column 10a extends upward from the test table 10b.

  The support 12 is supported by the support 10a. The support 12 is movable in the vertical direction with respect to the column 10a.

  The pressing tool 14 is fixed to the test table 10b. The pressing tool 14 includes a pressing surface 14a facing upward. The pressing surface 14a is a flat surface. The pressing surface 14a intersects the vertical direction vertically. The axial width of the pressing surface 14a is larger than the tread width from one tread end to the other tread end. As the support 12 moves upward, the support 12 moves away from the pressing tool 14. As the support 12 moves downward, the support 12 approaches the pressing tool 14.

  Although not shown, the support 12 can fix the rim 8. As a result, the support 12 can support the tire assembly 2. The support 12 allows the tire assembly 2 to move in a direction approaching the pressing tool 14 and a direction moving away from the pressing tool 14.

  Although not shown, the testing machine 4 includes a control device and an information processing device. The control device controls the vertical movement of the support 12. The control device includes a position sensor and a load sensor. This load sensor can measure the load applied to the tire assembly 2. This position sensor can detect the vertical position of the tire assembly 2. This control device can measure the amount of vertical displacement of the support 12 by using this position sensor.

  The information processing apparatus includes an input unit, a storage unit, a calculation unit, and an output unit. An example of this information processing apparatus is a computer. In the information processing device, the input unit receives data from the control device. The arithmetic unit analyzes using the data. The computing unit determines the evaluation result based on the analysis result. The storage unit stores data and evaluation results. The output unit outputs this evaluation result. For example, the input unit is an interface board, the storage unit is a hard disk, the calculation unit is a CPU, and the output unit is a display. A printer may be used as the output unit together with the display or instead of the display.

  Hereinafter, a tire stiffness evaluation method according to an embodiment of the present invention will be described mainly with reference to FIGS. 1 and 22. This rigidity feeling evaluation method includes a preparation process, a measurement process, and an evaluation process.

In this preparation step, the tire 6 and the rim 8 are prepared. The tire 6 is incorporated into the rim 8, and the tire assembly 2 is obtained. The tire assembly 2 is filled with air. Thereafter, the pressure is reduced, and the air pressure of the tire assembly 2 is brought to atmospheric pressure. For example, the tire assembly 2 is brought to atmospheric pressure after being brought to a normal internal pressure. By setting the normal internal pressure, the tire 6 is incorporated in a normal positional relationship with the rim 8. The air pressure when filling the tire assembly 2 does not necessarily have to be a normal pressure, as long as the tire 6 and the rim 8 have a normal positional relationship.

  In this measurement process, the rim 8 is fixed to the support 12 of the testing machine 4. The tire assembly 2 brought to atmospheric pressure is attached to the testing machine 4. The tire assembly 2 is attached so that the axial direction is horizontal and the radial direction is vertical. The tire assembly 2 is supported by the support 12 so as to be movable in the vertical direction.

  The control device transmits a control signal to the support 12. The control device moves the support 12 downward. The support 12 moves the tire assembly 2 downward. When the support 12 starts moving, the position sensor detects the position of the tire assembly 2. This position sensor may detect the position of the support 12 as the position of the tire assembly 2. The load sensor measures the load applied to the tire assembly 2. The load sensor may measure the load received by the support 12 as the load of the tire assembly 2.

  The support 12 gradually approaches the pressing tool 14. The tread surface 6 a of the tire 6 contacts the contact surface 14 a of the pressing tool 14. In the present invention, the position where the tread surface 6a and the contact surface 14a contact each other is referred to as the ground contact position of the tire assembly 2.

  Further, the support 12 moves the tire assembly 2 downward from the ground contact position. The support 12 presses the tire 6 against the pressing tool 14. The tread surface 6a is pressed against the contact surface 14a. Thereby, the tire 6 is deformed. The load sensor measures the load load of the tire assembly 2. The position sensor detects the position of the tire assembly 2.

  When the load on the tire assembly 2 reaches a preset maximum value, the control device stops the downward movement of the support 12. The load sensor ends the measurement. The position sensor ends position detection. In the present invention, the position where the support 12 stops moving downward is referred to as the end position.

  This end position may be set based on the descending end of the support 12 in advance, instead of the maximum value of the load. When the support 12 reaches the descending end, the control device may stop the downward movement of the support 12. At this time, the load sensor may end the measurement, and the position sensor may end the position detection.

  The control device transmits the load load data and position data of the tire assembly 2 to the information processing device. The information processing apparatus stores position data from the ground contact position to the end position and load load data corresponding to the position data.

  The information processing apparatus calculates the displacement amount D of the tire assembly 2 from the contact position at each position from the stored position data. This displacement amount D represents a position where the ground contact position is 0 of the origin. This displacement amount D represents the deformation amount of the tire assembly 2. This load is the load F received by the tire assembly 2. The information processing apparatus calculates a function of the displacement amount D and the load F, where the horizontal axis is the displacement amount D and the vertical axis is the load F.

  A thick solid line S1 in FIG. 3 is a graph of a function of the displacement amount D and the load F of the tire assembly 2. In this graph S1, the load F increases as the displacement amount D increases from the origin of the ground contact position. Further, when the displacement amount D increases, the graph S1 reaches the first inflection point. The amount of displacement at this first inflection point is D1, and the load is F1. The load F decreases as the displacement amount D increases from the first inflection point. When the displacement amount D increases from the displacement amount D1, the graph S1 reaches the second inflection point. The amount of displacement at this second inflection point is D2, and the load is F2. The load F increases as the displacement amount D increases from the second inflection point.

  The information processing apparatus obtains the first inflection point and the second inflection point from the function of the displacement amount D and the load F. For example, the information processing apparatus differentiates a function of the displacement amount D and the load F to obtain a first inflection point and a second inflection point. This first inflection point is the first inflection point when the displacement amount D is increased from zero. The second inflection point is the next inflection point after the first inflection point when the displacement amount D is increased.

  The information processing apparatus obtains a first index A1 and a second index A2 for evaluating rigidity. The information processing apparatus determines the load F1 at the first inflection point as the first index A1.

  The information processing apparatus determines a predetermined range in which the displacement amount is further increased beyond the second inflection point. A region surrounded by a dotted line M2 in FIG. 3 illustrates a region where the displacement amount is in a predetermined range. An inclination F / D of a predetermined range of this function is obtained. This predetermined range of gradient F / D is determined as the second index A2.

For example, the predetermined range is set to a range between the displacement amounts D3 and D4. At this time, the displacement amounts D3 and D4 are larger than the displacement amount D2, and the displacement amount D4 is larger than the displacement amount D3. The information processing apparatus obtains the load F3 at the position where the displacement amount is D3. The load F4 at the position where the displacement amount is D4 is obtained. The information processing apparatus obtains the inclination F / D by the following equation (1).
F / D = (F4-F3) / (D4-D3) (1)

  Here, although the example which calculates | requires inclination F / D showing 2nd parameter | index A2 was shown by Formula (1), the method of calculating | requiring this inclination F / D is not restricted to Formula (1). For example, in a predetermined range from the displacement amount D3 to the displacement amount D4, the graph S1 shown in FIG. 3 may be approximated to a straight line, and the slope F / D may be obtained from this approximate straight line.

  The information processing apparatus stores the reference value Fs of the first index A1 and the reference value (F / D) s of the second index A2. It is determined whether or not the value F1 of the first index A1 of the tire assembly 2 is greater than or equal to the reference value Fs. It is determined whether the value F / D of the second index A2 of the tire assembly 2 is greater than or equal to a reference value (F / D) s. When the first index A1 of the tire assembly 2 is equal to or greater than the reference value Fs and the second index A2 is equal to or greater than the reference value (F / D) s, the information processing apparatus has a good rigidity feeling of the tire assembly 2. Judge.

  The reference value Fs of the first index A1 and the reference value (F / D) s of the second index A2 may be obtained from the reference tire. A reference tire assembly is prepared by incorporating the reference tire into a regular rim. The load at the first inflection point of the reference tire assembly is set to the reference value Fs. The inclination F / D in the range of the displacement amount D3 to D4 of the reference tire assembly is set to the reference value (F / D) s. The sense of rigidity of the tire assembly 2 may be evaluated based on the reference value Fs and the reference value (F / D) s obtained from the reference tire.

  FIG. 3 shows a graph of the tire assembly 16, the tire assembly 18, and the tire assembly 20 as with the tire assembly 2. A solid line S2 in FIG. 3 is a graph of a function of the displacement amount D and the load F of the tire assembly 16. A two-dot chain line S3 is a graph of a function of the displacement amount D and the load F of the tire assembly 18. A dotted line S4 is a graph of a function of the displacement amount D and the load F of the tire assembly 20.

  As shown in FIG. 3, in the graphs S2, S3, and S4, similarly to the graph S1, the load F increases as the displacement amount D increases from the origin of the ground contact position. Further, when the displacement amount D increases, the first inflection point is reached. The load F decreases as the displacement amount D increases from the first inflection point. When the displacement amount D further increases, the second inflection point is reached. The load F increases as the displacement amount D increases from the second inflection point. As described above, in the tire assembly in the atmospheric pressure state, the graph of the function of the displacement amount D and the load F has the first inflection point and the second inflection point.

  In this evaluation process, the first inflection point and the second inflection point in the graph of the function of the displacement amount D and the load F are obtained. In this evaluation method, the sense of rigidity is evaluated based on the first index A1. Thereby, the initial rigidity feeling until reaching the first inflection point is evaluated. Furthermore, the feeling of rigidity is evaluated based on the second index A2. A feeling of rigidity within a predetermined range beyond the second inflection point is evaluated. Thereby, the initial rigidity feeling and the rigidity feeling after the displacement amount exceeds the second inflection point are evaluated. In this method, the rigidity feeling of the tire assembly brought to the atmospheric pressure state is appropriately evaluated.

  In this method, the feeling of rigidity of the tire assembly brought to the atmospheric pressure state is evaluated. From the sense of rigidity of the tire assembly, the sense of rigidity of the tire is evaluated. Usually, a purchaser of a commercially available tire confirms a feeling of rigidity in a state where air is not filled. Since this method is in the atmospheric pressure state, an evaluation close to the rigidity of a commercially available tire can be obtained.

  In this measurement step, the flat surface 14 a is in contact with the tread surface 6 a from the one tread end to the other tread end in the axial direction of the tire 6. In this measurement process, the evaluation of the local rigidity of the tire 6 is suppressed. In this measurement process, the overall rigidity of the tread and sidewalls of the tire 6 is evaluated.

From the viewpoint of evaluating the overall rigidity of the tire 6, it is preferable that the plane area of the pressing surface 14a is wide. In this evaluation method, the area of the pressing surface 14a is obtained by integrating the tread width from one toled end in the axial direction of the tire 6 to the other tread end and the length in the front-rear direction of the pressing surface 14a. The area of 14a is preferably 25 cm ² or more. In this evaluation method, there is an upper limit in the length in the front-rear direction of the pressing surface 14a that can be grounded to the tread surface 6a. In the tread width, the area of the plane of the pressing surface 14a is preferably 100 cm ² or less.

  In the present invention, when it can be clearly identified by the edge of the tread surface 6a in appearance, this edge is set as the tread end. When it is difficult to identify the appearance, the tire 6 is grounded to the flat surface on the outermost side in the axial direction when the tire 6 is brought into contact with the flat surface with a normal load in a state in which the tire 6 is incorporated in the normal rim and has a normal internal pressure. The grounding end is the tread end. At this time, it is brought into contact with a plane with a camber angle of 0 °. The tread width of the tire 6 is from one tread end determined in this way to the other tread end.

  In this measurement process, it is preferable that the maximum value of the load load of the tire assembly 2 is set to the same level as the maximum value of the load load when the person deforms the tire 6. Thereby, an evaluation result close to sensory evaluation can be obtained. From this viewpoint, the maximum value of the load is preferably 0.70 kN or less, more preferably 0.65 kN or less. On the other hand, from the viewpoint of obtaining the first index A1 and the second index A2, the maximum value of the load is preferably 0.45 kN or more, more preferably 0.50 kN or more, and particularly preferably 0.55 kN. That's it. For example, the maximum value of the load is set to 0.6 kN.

  As the second index S2, an inclination within a predetermined range in which the deformation amount is further increased beyond the second inflection point is used. In the vicinity of the second inflection point, the inclination changes. It is preferable that a predetermined range is provided in the range of the displacement amount sufficiently separated from the second inflection point. From this viewpoint, at the lower limit of the predetermined range, the amount of displacement from the second inflection point is preferably 5 mm or more, and more preferably 10 mm or more. On the other hand, if it is far away from the second inflection point, the error in inclination tends to increase. From the viewpoint of reducing the inclination error, the amount of displacement from the inflection point is preferably 25 mm or less, and more preferably 20 mm or less, at the upper limit of the predetermined range.

  In this evaluation step, when the first index A1 is equal to or greater than the reference value Fs and the second index S2 is equal to or greater than the reference value (F / D) s, the rigidity of the tire 6 is evaluated as good. It is evaluated whether or not the first index A1 is greater than or equal to the reference value Fs. It is evaluated whether or not the second index A2 is greater than or equal to the reference value (F / D) s. This evaluation method enables an objective quantitative evaluation. This evaluation excludes subjective variations.

  The black circles in FIG. 4 indicate the relationship between the load F that is the first index A1 and the inclination F / D that is the second index A2 of the tire assembly 2. The black triangle mark indicates the relationship between the load F that is the first index A1 and the inclination F / D that is the second index A2 of the tire assembly 16. Similarly, black square marks indicate the relationship between the load F, which is the first index A1, and the slope F / D, which is the second index A2, of the tire assembly 18. The black rhombus mark indicates the relationship between the load F that is the first index A1 and the inclination F / D that is the second index A2 of the tire assembly 20.

  For example, the tire assembly 18 may be a reference tire assembly. The load F obtained from the tire assembly 18 may be the reference value Fs, and the inclination F / D may be equal to or greater than the reference value (F / D) s. Based on the reference value reference value Fs and the reference value (F / D) s, the rigidity feeling of other tire assemblies may be evaluated.

  As shown in FIG. 4, the tire stiffness senses can be ranked based on the magnitude relationship between the first index A1 and the second index A2. In FIG. 4, the tire 6 of the tire assembly 2 has the highest rigidity. Next, the tire assembly 16 has a high tire rigidity. Next, the tire assembly 18 has a high tire rigidity. The tire of the tire assembly 20 has the lowest rigidity.

  In this rigidity feeling evaluation method, it is not always necessary to determine whether the rigidity feeling is good or bad. As shown in FIG. 4, the tire stiffness feelings of a plurality of tire assemblies may be compared and ranked. The first index A1 and the second index A2 of the plurality of tire assemblies may be measured, and the tire stiffness may be ranked based on the magnitude relationship between the first index A1 and the second index A2.

  In the present invention, the regular rim means a rim defined in the standard on which the tire 2 depends. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims. The normal internal pressure means an internal pressure defined in a standard on which the tire 2 depends. “Maximum air pressure” in JATMA standard, “maximum value” published in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA standard, and “INFLATION PRESSURE” in ETRTO standard are normal internal pressures. The normal load means a load determined in the standard on which the tire 2 depends. “Maximum value” published in “Maximum load capacity” in the JATMA standard, “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the TRA standard, and “LOAD CAPACITY” in the ETRTO standard are normal loads.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[sensory evaluation]
Each tire assembly 2, tire assembly 16, tire assembly 18, and tire assembly 20 was subjected to a sensory evaluation. The evaluation results of the feeling of rigidity were ranked. The results are shown in Table 1. As a result, the smaller the number, the higher the sense of rigidity. S1, S2, S3, and S4 in Table 1 represent the tire assembly 2, the tire assembly 16, the tire assembly 18, and the tire assembly 20, respectively.

[Test 1]
The rigidity feeling of each of the tire assembly 2, the tire assembly 16, the tire assembly 18, and the tire assembly 20 was evaluated by the rigidity feeling evaluation method according to the present invention. The stiffness of each tire is represented by an index with the stiffness of the tire assembly 2 being 100. This index may be determined based on the total value of the first index A1 and the second index A2, for example. This index has higher rigidity as the number increases. The results are shown in Table 1.

[Comparison test 1]
The tire assembly 2 was filled with air and brought to an internal pressure state of 10% of the normal internal pressure. A pressing tool having a convex spherical contact surface was prepared. The contact surface of the pressing tool was in contact with the axial center of the tread surface of the tire assembly 2. A load change amount dF for pressing the pressing tool and a tire deformation amount δ were measured. A coefficient dF / δ was obtained from the deformation amount dF and the deformation amount δ. The coefficient dF / δ was determined for the tire assembly 16, the tire assembly 18, and the tire assembly 20 in the same manner as the tire assembly 2. These coefficients dF / δ are expressed as an index with the tire assembly 2 as 100. This index has higher rigidity as the number increases. The results are shown in Table 1.

[Comparison test 2]
The tire assembly 2 was filled with air and brought into a normal internal pressure state. The tread surface of the tire assembly 2 was brought into contact with a flat surface. A load change dF and a tire deformation amount δ by which the tire assembly 2 is pressed against a flat surface were measured. A coefficient dF / δ was obtained from the deformation amount dF and the deformation amount δ. The coefficient dF / δ was determined for the tire assembly 16, the tire assembly 18, and the tire assembly 20 in the same manner as the tire assembly 2. These coefficients dF / δ are expressed as an index with the tire assembly 2 as 100. This index has higher rigidity as the number increases. The results are shown in Table 1.

  As shown in Table 1, the evaluation result of Test 1 coincided with the result of sensory evaluation. Furthermore, in Test 1, compared with Comparative Test 1 and Comparative Test 2, a large difference was confirmed in the evaluation results of the feeling of rigidity. In the comparative test 1, the difference in the evaluation results of the feeling of rigidity was slight. In Comparative Test 2, the difference in the evaluation results of the feeling of rigidity was larger than that of Comparative Test 1, but smaller than that of Test 1. In this stiffness evaluation method of Test 1, an evaluation result closer to the sensory evaluation is obtained. The rigidity evaluation method of test 1 makes it easier to evaluate the rigidity of the tire than the methods of comparison test 1 and comparison test 2.

  According to the rigidity evaluation method of the present invention, the tire rigidity can be quantitatively evaluated. From this evaluation result, the superiority of the present invention is clear.

DESCRIPTION OF SYMBOLS 2 ... Tire assembly 4 ... Test machine 6 ... Tire 6a ... Tread surface 8 ... Rim 10 ... Mount 12 ... Support body 14 ... Pressing tool 14a ... Press surface

Claims (6)

A preparation step in which a tire assembly in which a tire is incorporated in a rim and an air pressure is brought to an atmospheric pressure is prepared;
A measurement process in which the tread surface of the tire assembly is brought into contact with the pressing surface to measure the displacement amount and load load of the tire assembly;
An evaluation process for evaluating the rigidity of the tire based on the relationship between the displacement and the load,
In this evaluation process, when the horizontal axis is the displacement amount and the vertical axis is the load load, the first and second inflection points of the graph of the function of the displacement amount and the load load are obtained,
This first inflection point is the first inflection point when the displacement is increased from 0,
This second inflection point is the next inflection point after the first inflection point when the displacement is increased,
The load at this first inflection point is the first index,
The inclination of the predetermined range in which the displacement amount is further increased beyond the second inflection point is used as the second index.
A tire stiffness evaluation method in which tire stiffness is evaluated based on the first index and the second index. The pressing surface of the measuring step is a plane,
The rigidity evaluation method according to claim 1, wherein the pressing surface is in contact with a tread surface from one tread end in the axial direction of the tire to the other tread end. The rigidity evaluation method according to claim 2, wherein an area obtained by integrating the length in the front-rear direction of the pressing surface and the tread width from one tread end to the other tread end is 25 cm ² or more and 100 cm ² or less.   The rigidity evaluation method according to any one of claims 1 to 3, wherein, in the measurement step, the maximum value of the load is 0.45 kN or more and 0.7 kN or less.   The rigidity evaluation method according to any one of claims 1 to 4, wherein the inclination of the predetermined range is an inclination of a range in which a displacement amount from the second inflection point is set to 5 mm or more and 25 mm or less.   6. The tire according to claim 1, wherein the tire stiffness is evaluated as good when the first index is equal to or greater than a predetermined first reference value and the second index is equal to or greater than a predetermined second reference value. The rigidity evaluation method described in 1.

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