JP6110129B2 - 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. A purchaser of a commercially available tire may touch the tire to check the tire stiffness. For example, a palm is pressed against a tread portion, a sidewall portion, or the like of a tire. A feeling of rigidity is judged from the deformation state of the tire and the feeling received by the hand.

  In general, tires with high rigidity are preferred. Depending on the purchaser, this sense of rigidity is one of the criteria for selecting a tire. In particular, tires for four-wheel drive vehicles tend to prefer tires with a high rigidity.

JP-A-8-26188

  This tire stiffness is obtained by sensory evaluation. This feeling of rigidity is evaluated by human sensitivity. This feeling of rigidity is a subjective evaluation. This rigidity is likely to vary depending on the person to be evaluated. Conventionally, there has been no method for objectively evaluating this feeling of rigidity. This feeling of rigidity has not been quantitatively evaluated.

  Tire stiffness and tire stiffness are different. The rigidity is evaluated in a state where the tire is filled with air of normal internal pressure. The state of the tire to be evaluated is greatly different depending on the rigidity in the tire use state and the rigidity in the state where the air is not filled. It is difficult to evaluate the rigidity feeling from the result of the rigidity evaluation.

  An object of the present invention is to provide a method for accurately and quantitatively evaluating the rigidity of a tire.

  The tire stiffness evaluation method according to the present invention includes a measurement step in which the tire spring constant is measured. In this measurement process, the tire is sandwiched between the support jig for supporting the tire and the pressing tool pressed against the tire. Due to this sandwiching, a load is applied to the tire. The tire deformation amount δ from the state in which the load F1 is applied to the tire to the state in which the load F2 is applied is measured. A spring constant from the load F1 to the load F2 is measured from the loads F1 and F2 and the deformation amount δ. The ratio (F1 / F) between the load F1 and the normal load F of the tire is 0.10 or more. The ratio (F2 / F) between the load F2 and the normal load F is 0.20 or less.

  Preferably, the stiffness evaluation method includes an assembly preparation step prior to the measurement step. In the assembly preparation step, a regular rim for the tire is prepared. This tire is assembled into a regular rim to form a tire assembly. In the measurement step, the regular rim is used as a support jig, and the regular rim and the pressing tool sandwich the tire in the radial direction. The spring constant in the radial direction of the tire is measured.

  Preferably, in the assembly preparation step of this rigidity feeling evaluation method, the tire assembly is filled with air so as to have the air pressure P1. The ratio (P1 / P) between the air pressure P1 and the normal internal pressure P of the tire is 0.08 or more and 0.30 or less.

  Preferably, in the assembly preparatory step, the tire assembly is filled with air so that the pressure exceeds the air pressure P1, and then the pressure is reduced to the air pressure P1.

  Preferably, in the measuring step of the rigidity evaluation method, the tip of the pressing tool is formed in a spherical shape. The spherical radius is 15 mm or more and 30 mm or less.

  Preferably, in the measurement step of the rigidity evaluation method, the pressing tool presses the center in the axial direction of the tread.

  Preferably, in the measurement process of the rigidity evaluation method, the pressing tool presses the position at the distance T in the axial direction from the equator plane with respect to the tread width Wt. The ratio (T / Wt) of the distance T to the tread width Wt is set to 0.40 or more and 0.45 or less.

  Preferably, in the measurement process of the rigidity evaluation method, the support jig and the pressing tool sandwich the tire in the axial direction. This support jig supports one sidewall portion in the axial direction of the tire. This pressing tool presses the other sidewall portion in the axial direction of the tire. The spring constant in the axial direction of the tire is measured.

  Preferably, in the measurement step of the rigidity feeling evaluation method, one of the support jig and the pressing tool presses the position of the height H1 in the radial direction of the tire in the sidewall portion. The ratio (H1 / H) between the height H1 and the tire height H is set to 0.6 or more and 0.8 or less. The other of the support jig and the pressing tool is in contact with the position of the sidewall portion having the maximum axial width.

  Preferably, either one of the support jig and the pressing tool includes a base portion and a pressing portion. The position of the pressing portion can be changed in the radial direction of the tire with respect to the base portion. The pressing portion presses the position of the height H1 in the radial direction of the tire.

  In the tire stiffness evaluation method according to the present invention, the tire stiffness can be quantitatively evaluated. This evaluation of rigidity gives an evaluation result close to the rigidity obtained by human sensory evaluation.

FIG. 1 is an explanatory diagram showing a state of a tire stiffness evaluation method according to an embodiment of the present invention. FIG. 2A and FIG. 2B are explanatory diagrams of the stiffness evaluation method of FIG. FIG. 3 is an explanatory diagram of a tire stiffness evaluation method according to another embodiment of the present invention. FIG. 4A and FIG. 4B are explanatory diagrams of a tire stiffness evaluation method according to still another embodiment of the present invention. FIG. 5 is an explanatory diagram of a tire stiffness evaluation method according to still another embodiment of the present invention.

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

  FIG. 1 shows a tire assembly 2 and a deflection machine 4. The tire assembly 2 is attached to a deflection machine 4. In the following description, the vertical direction is described as the vertical direction in FIG. 1 unless otherwise specified.

  FIG. 2 is an explanatory diagram of the stiffness evaluation method shown 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 deflection machine 4 in FIG. 1 includes a gantry 10, a support body 12, a load load body 14, and a pressing tool 16. A support 12 is fixed to the top of the gantry 10. The load load body 14 includes a main body 18, a rod 20, and a head 22. A main body 18 is fixed to the lower part of the gantry 10. A head 22 is fixed to the upper end of the rod 20. The pressing tool 16 is fixed to the upper surface 22 a of the head 22.

  Although not shown, the support 12 can fix the rim 8. As a result, the support 12 can support the tire assembly 2. The rod 20 is movable in the vertical direction with respect to the main body 18.

  Although not shown, the deflection machine 4 includes a control device and an information processing device. The control device controls the load load body 14. The control device includes a position sensor and a load sensor. The control device controls the vertical movement of the rod 20. The control device can move the rod 20 upward with a predetermined load. The control device can detect the vertical position of the rod 20 and measure the amount of movement in the vertical direction.

  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 with reference to FIGS. 1 and 2. This stiffness evaluation method includes an assembly preparation step, a measurement step, and a determination step.

In the assembly 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. The air pressure of the tire assembly 2 is set to the air pressure P1. Here, the tire assembly 2 is brought to the air pressure P1 after the air pressure exceeding the air pressure P1. For example, in the tire assembly 2, the air is filled up to the normal internal pressure P of the tire 6. Thereafter, the pressure is reduced from the air pressure P to the air pressure P1.

  In the measurement process, the rim 8 is fixed to the support 12 of the deflection machine 4. The tire assembly 2 with the air pressure set to P1 is installed in the deflection machine 4. The tire assembly 2 is fixed so that the axial direction is horizontal and the radial direction is vertical. Here, the rim 8 is a supporting jig that supports the tire 6. The rim 8 supports the tire 6 when the pressing tool 16 is pressed upward against the tire 6.

  The control device transmits a load load start signal to the load load body 14. The load load body 14 pushes the rod 20 upward with the load F1. The pressing tool 16 fixed to the upper surface of the head 22 contacts the tread surface 6 a of the tire 6. The pressing tool 16 presses the tread surface 6 a toward the center of the tire 6 in the radial direction. The pressing tool 16 presses the center of the tire 6 in the axial direction.

  As shown in FIG. 2A, the pressing tool 16 is pressed against the tire 6 with a load F1. The vertical position of the rod 20 is determined in a state where the tire 6 is deformed and the pressing force and the reaction force are balanced. The position of the rod 20 at the time of this load F1 is detected.

  As shown in FIG. 2B, the pressing tool 16 is pressed against the tire 6 with the load F2. This load F2 is larger than the load F1. The rod 20 moves further upward from the state where the pressing force and the reaction force are balanced by the load F1. With the load F2, the vertical position of the rod 20 is determined in a state where the tire 6 is deformed and the pressing force and the reaction force are balanced. The position of the rod 20 at this load F2 is detected.

  The difference between the position of the rod 20 at the load F1 and the position of the rod 20 at the load F2 is obtained. This difference is the deformation amount δ of the tire 6 from the load F1 to the load F2. The tread 6 b of the tire 6 is deformed in the vertical direction by a deformation amount δ by pressing the pressing tool 16.

The information processing apparatus calculates the spring constant K from the load F1, the load F2, and the deformation amount δ. The spring constant K is obtained by the following equation.
K = (F2-F1) / δ

The information processing apparatus calculates the stiffness evaluation value S1 from the spring constant K. This evaluation value S1 is obtained by the following equation.
S1 = C1 · (K / P1)
This C1 is a predetermined coefficient. In this evaluation value S1, the influence of the air pressure P1 on the evaluation value S1 is suppressed by dividing the spring constant K by the air pressure P1.

  In the determination step, the information processing apparatus compares the evaluation value S1 with the reference value Sa and evaluates the rigidity of the tire 6. For example, the reference value Sa is set to 1.0. If the evaluation value S1 is greater than or equal to the reference value Sa, it is evaluated that a sufficient rigidity is obtained. If the evaluation value S1 is less than the reference value Sa, it is evaluated that sufficient rigidity is not obtained.

  This reference value Sa is determined in advance. For example, a reference tire that has already had a good rigidity feeling in sensory evaluation is prepared. An evaluation value S1 of this reference tire is obtained. This evaluation value S1 may be the reference value Sa. The coefficient C1 may be determined so that the evaluation value S1 of the reference tire is 1.0.

  In the measurement process, the deformation amount δ of the tire 6 is calculated based on the state in which the tire 6 is deformed with the load F1. By using this deformed state as a reference, variation in the reference position of the rod 20 is suppressed. Thereby, variation in the value of the deformation amount δ is suppressed. From this viewpoint, the ratio (F1 / F) between the load F1 and the normal load F of the tire 6 is 0.10 or more.

  If the load F2 is too large, the deformation amount δ becomes too large. If the load F2 is too large, a difference in deformation amount δ hardly occurs between tires having a difference in rigidity. From this viewpoint, the ratio (F2 / F) between the load F2 and the normal load F of the tire 6 is 0.20 or less.

  The deformation amount δ of the tire 6 is measured in a state where the tire 6 is incorporated in the rim 8. Since the tire 6 is stably supported by the rim 8, variations in the deformation amount δ in the radial direction are suppressed. Since the rim 8 is a regular rim, the variation in the deformation amount δ is further suppressed.

  The tire assembly 2 is filled with air. Thereby, the tire 6 is supported by the rim 8 at a regular position. By filling with air, the tire 6 pressed by the pressing tool 16 is prevented from coming off from the rim 8. From this viewpoint, the ratio (P1 / P) of the air pressure P1 to the normal internal pressure P is preferably 0.08 or more. More preferably, this ratio (P1 / P) is 0.09 or more.

  On the other hand, by suppressing the air pressure of the tire assembly 2 to a low level, an evaluation result close to a sense of rigidity by sensory evaluation can be obtained. In this respect, the ratio (P1 / P) is preferably equal to or less than 0.30. More preferably, this ratio (P1 / P) is 0.20 or less, particularly preferably 0.15 or less.

  In this evaluation method, after the tire assembly 2 is filled with air up to an air pressure higher than the air pressure P1, the pressure is reduced to the air pressure P1. By filling the air up to a high air pressure, the tire 6 is assembled in a normal position with respect to the rim 8. Thereby, even if the air pressure P1 is low, the tire 6 is incorporated into the rim 8 at a regular position. As a result, variation in the deformation amount δ is suppressed. Preferably, after the tire assembly 2 is pressurized to the normal internal pressure P of the tire 6, the pressure is reduced to the air pressure P1. As a result, the tire 6 is more reliably assembled to the rim 8 at a normal position.

  In general, the purchaser presses the heel portion of the palm against the tire 6 to evaluate the rigidity of the tire 6. The heel portion of the palm is a portion of the palm close to the wrist. In other words, the heel part of the palm is the bulging part of the thumb ball and the little finger ball of the hand. By making the tip of the pressing tool 16 into a spherical shape, the tire 6 deforms close to a state in which the heel portion of the palm is pressed. Thereby, the evaluation result close | similar to the feeling of rigidity by a palm is obtained. From this viewpoint, the spherical radius at the tip of the pressing tool is preferably 15 mm or more. The radius is preferably 30 mm or less.

  With reference to FIG. 3, a stiffness evaluation method for a tire 6 according to another embodiment of the present invention will be described. Here, a configuration different from the stiffness evaluation method shown in FIGS. 1 and 2 will be described. The description of the same configuration as the stiffness evaluation method shown in FIGS. 1 and 2 is omitted.

  In this evaluation method, the fixing position of the pressing tool 16 is changed with respect to the head 22. The pressing tool 16 abuts on the axially outer position of the tread surface 6a.

  A double arrow Wt in FIG. 3 indicates the tread width in the axial direction. The tread width Wt is a distance from one tread end to the other tread end. A double-headed arrow T is an axial width from the equatorial plane CL to a position where the pressing tool 16 and the tread surface 6a abut. The tread width Wt and the width T are measured along the tread surface 6a.

  The pressing tool 16 contacts the tread surface 6a of the tire 6 at the position of the width T. The pressing tool 16 presses the tread surface 6 a inward in the radial direction of the tire 6. At this time, the spring constant K is calculated.

  In this evaluation method, the ratio of the distance T to the tread width Wt (T / Wt) is preferably 0.40 or more. Thereby, the feeling of rigidity in the radial direction of the sidewall portion 6c can be appropriately evaluated. On the other hand, in the vicinity of the tread end, the influence of the deformation of the tread surface 6a is large. The deformation of the tread surface 6a tends to affect the evaluation of the rigidity in the radial direction of the sidewall portion 6c. In this respect, the ratio (T / Wt) is preferably 0.45 or less.

The information processing apparatus calculates the evaluation value S2 of the stiffness feeling from the spring constant K. This evaluation value S2 is obtained by the following equation. This A is the flatness ratio of the tire 6.
S2 = C2 · ((K · A) / P1) / 100

  C2 is a predetermined coefficient. The evaluation value S2 is suppressed from being influenced by the air pressure P1 by dividing the spring constant K by the air pressure P1. Further, the evaluation value S2 is measured in the vicinity of the tread edge. For this reason, the evaluation value S2 is easily affected by the flatness ratio A. The evaluation value S2 is obtained as a product of the spring constant K and the flattening rate A of the tire 6, so that the influence of the flattening rate A is suppressed.

  The information processing apparatus evaluates the sense of rigidity of the tire 6 by comparing S2 with the reference value Sb. For example, the reference value Sb is set to 1.0. If the evaluation value S2 is 1.0 or more, it is evaluated that sufficient rigidity is obtained. If the evaluation value S2 is less than 1.0, it is evaluated that sufficient rigidity is not obtained.

  This reference value Sb is determined in advance. For example, a reference tire that has already been confirmed to have good rigidity by sensory evaluation is prepared. An evaluation value S2 of this reference tire is obtained. This evaluation value S2 may be the reference value Sb. The coefficient C2 may be determined so that the evaluation value S2 becomes 1.0.

  With reference to FIG. 4A and FIG. 4B, a stiffness evaluation method for a tire 6 according to still another embodiment of the present invention will be described. Here, a configuration different from the stiffness evaluation method shown in FIGS. 1 and 2 will be described. The description of the same configuration as the stiffness evaluation method shown in FIGS. 1 and 2 is omitted.

  In this evaluation method, the head 22 is used as a pressing tool. A support jig 24 is attached to the support 12. The support jig 24 is fixed to the support 12. In this evaluation method, the support jig 24 comes into contact with one sidewall portion 6 c above the tire 6.

  The head 22 contacts the other sidewall portion 6 c below the tire 6. The head 22 is in contact with the position of the maximum width in the axial direction of the sidewall portion 6c. The maximum axial width of the sidewall portion 6 c is measured on the outermost surface of the sidewall portion 6 c in the axial direction of the tire 6. A double arrow D in FIG. 4A indicates the outer diameter of the tire 6. The surface located at the maximum axial width of the sidewall portion 6c is a surface that comes into contact with the flat surface wider than the outer diameter D when the tire 6 is pressed in the axial direction.

  As shown in FIG. 4B, the head 22 presses the entire circumference in the circumferential direction of the tire 6 at the position of the maximum width in the axial direction of the sidewall portion 6c. The support jig 24 presses a part of the circumferential direction of the tire 6 as shown in FIG.

  A point Pt in FIG. 4A is an intersection of the tread surface 6a of the tire 6 and the equator plane CL. This point Pt is a point located on the outermost side in the radial direction of the tire 6. A double arrow H is a height from the bead base line BBL to the point Pt. The point Pp is a point where the support jig 24 and the tire 6 abut. A double arrow H1 is the height from the bead base line BBL to the point Pp. The height H and the height H1 are measured as the distance in the radial direction of the tire 6.

  The head 22 contacts the sidewall portion 6c of the tire 6 and presses the tire 6 upward. The support jig 24 supports the tire 6 downwardly against the pressing of the head 22.

  The load load body 14 pushes the rod 20 upward with the load F1. The head 22 is pressed against the tire 6 with the load F1. The vertical position of the rod 20 is determined in a state where the tire 6 is deformed and the pressing force and the reaction force are balanced.

  The load load body 14 pushes the rod 20 upward with the load F2. The rod 20 moves further upward from the state where the pressing force and the reaction force are balanced by the load F1. With the load F2, the vertical position of the rod 20 is determined in a state where the tire 6 is deformed and the pressing force and the reaction force are balanced.

  The tire 6 is deformed in the vertical direction by the deformation amount δ when the head 22 is pressed. The information processing apparatus calculates the spring constant K from the load F1, the load F2, and the deformation amount δ. The spring constant K is obtained as an axial spring constant of the sidewall portion 6c.

The information processing apparatus calculates a stiffness evaluation value S3 from the spring constant K. This evaluation value S3 is obtained by the following equation, where A is the flatness ratio of the tire 6.
S3 = C3 · (K · A) / 1000

  C3 is a predetermined coefficient. The evaluation value S3 is obtained as a product of the spring constant K and the flattening rate A of the tire 6, so that the influence of the flattening rate A is suppressed.

  In this evaluation method, the support jig 24 comes into contact with one sidewall portion 6c, the head 22 comes into contact with the other sidewall portion 6c, and the tire 6 is sandwiched. Thereby, the axial rigidity of the sidewall portion 6c of the tire 6 can be easily evaluated.

  In this evaluation method, the head 22 is in contact with the position of the maximum width in the axial direction of the sidewall portion 6c. The support jig 24 is in contact with the position of the height H1, that is, the position of the point Pp. By setting the ratio (H1 / H) to be 0.6 or more, the difference in rigidity of the tire 6 can be easily evaluated. Also in human sensory evaluation, it is easy to evaluate the difference in rigidity in the range from the maximum axial width of the tire 6 to the buttress portion. When the ratio (H1 / H) is 0.6 or more, an evaluation result close to human sensory evaluation can be obtained. By setting the ratio (H1 / H) to be 0.6 or more, it is possible to obtain a more accurate evaluation result by bringing the tire 6 into contact at the position of the maximum width in the axial direction. On the other hand, when the ratio (H1 / H) is set to 0.8 or less, the influence on the tread surface 6a side can be suppressed. Thereby, a more accurate evaluation result can be obtained.

  In the determination step, the information processing apparatus compares this S3 with the reference value Sc and evaluates the sense of rigidity of the tire 6. For example, the reference value Sc is set to 3.0. If the evaluation value S3 is greater than or equal to the reference value Sc, it is evaluated that a sufficient rigidity is obtained. If the evaluation value S3 is less than the reference value Sc, it is evaluated that sufficient rigidity is not obtained.

  This reference value Sc is predetermined. For example, a reference tire that has already been confirmed to have good rigidity by sensory evaluation is prepared. An evaluation value S3 of this reference tire is obtained. This evaluation value S3 may be set as the reference value Sc. The coefficient C3 may be determined so that the evaluation value S3 of the reference tire is 1.0.

  With reference to FIG. 5, a stiffness evaluation method for a tire 6 according to still another embodiment of the present invention will be described. Here, a configuration different from the stiffness evaluation method shown in FIGS. 4A and 4B will be described. The description of the same configuration as the stiffness evaluation method shown in FIGS. 4A and 4B is omitted.

  FIG. 5 shows the support jig 26. In this embodiment, a support jig 26 is used in place of the support jig 24 in the rigidity evaluation method of FIGS. 4 (a) and 4 (b). In this embodiment, other configurations are the same as those in the rigidity evaluation method in FIGS. 4 (a) and 4 (b).

  The support jig 26 includes a base portion 28 and a pair of pressing portions 30. The shape of the base portion 28 is a substantially rectangular plate shape in the plan view of FIG. A long hole 32 is formed in the base portion 28. The long holes 32 are respectively formed at both ends in the longitudinal direction of the base portion 28. The long hole 32 extends in the longitudinal direction of the base portion 28. Four long holes 32 are formed in the base portion 28.

  The pressing portion 30 is formed with a tip portion 34 that comes into contact with the tire. A pin 38 extends upward from the rear end portion 36 of the pressing portion 30. A stopper 40 is fixed to the tip of the pin 38.

  The pin 38 of the pressing portion 30 is slidably inserted into the long hole 32 of the base portion 28. Accordingly, the pressing portion 30 is movable in the longitudinal direction of the long hole 32 with respect to the base portion 28. The stopper 40 and the pressing portion 30 sandwich the base portion 28 so that the pressing portion 30 can be positioned in the longitudinal direction of the long hole 32 with respect to the base portion 28.

  In the support jig 26, the fixing position of the pressing portion 30 can be changed with respect to the base portion 28. The position of the pressing portion 30 can be changed in the radial direction of the tire 6 with respect to the base portion 28. Thereby, it is made easy to adjust so that the press part 30 may contact | abut at various positions with respect to various tires. As a result, the evaluation can be performed more easily than the rigidity evaluation method shown in FIGS. 4 (a) and 4 (b).

  Here, the head 22 is in contact with the sidewall portion 6c of the tire 6 in a plane, but the support jig 30 may be in contact with a plane. In this case, the head 22 may be provided with a pressing portion that can change the position in the radial direction of the tire 6 with respect to the base and the base.

  In the present invention, unless otherwise specified, the size and angle of each member of the tire 6 are measured in a state where the tire 2 is incorporated in a normal rim and the tire 2 is filled with air so as to have a normal internal pressure. At the time of measurement, no load is applied to the tire 2. In the present specification, the normal rim means a rim defined in a 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. In the present specification, the normal internal pressure means an internal pressure defined in a standard on which the tire 2 relies. “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. In the present specification, the normal load means a load defined in a standard on which the tire 2 depends. “Maximum value” published in “Maximum load capacity” in JATMA standard, “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA standard, and “LOAD CAPACITY” in 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.

[Test 1]
Commercial tires were prepared. The tire size is “LT265 / 70R16 117 / 114S”. The flatness ratio A of this tire is 70 (%). The normal internal pressure P of this tire was 550 (kPa), and the normal load was 14.2 (kPa). The spring constant of this commercially available tire was measured by the stiffness evaluation method shown in FIGS. This spring constant was measured by variously changing the air pressure P1 (kPa) of a commercially available tire. Here, the spring constant was measured five times at each air pressure P1. The average value Eave (N / mm) of the spring constant and the variance σ were calculated for each air pressure P1. A value of ((2 · σ) / Eave) was obtained from the average value Eave (N / mm) and the dispersion σ. This ((2 · σ) / Eave) is an index indicating the magnitude of variation in the measured value. The smaller this ((2 · σ) / Eave) value, the smaller the variation. The test results are shown in Table 1.

[Test 2]
In the same manner as in Test 1, the spring constant of a commercially available tire was measured by the stiffness evaluation method shown in FIG. A value of ((2 · σ) / Eave) was obtained from the average value Eave (N / mm) and the dispersion σ. The results are shown in Table 2.

  In Test 1 and Test 2, the ratio (P1 / P) is 0.08 or more and 0.30 or less, and ((2 · σ) / Eave) is 0.05 or less. The variation is small within the range of the internal pressure P1.

[Test 3]
Three types of tires, tires E1, E2, and E3, and a reference tire were prepared. These tires are evaluated for rigidity at the tread portion by sensory evaluation. In the sensory evaluation, the determination result of the tire E1 was good. The determination results of the tires E2 and E3 were poor. The determination result of this reference tire was good. In the sensory evaluation, the rigidity of the reference tire was smaller than the rigidity of the tire E1, and greater than the rigidity of the tires E2 and E3.

  With the stiffness evaluation method shown in FIGS. 1 and 2, the stiffness of the reference tire was evaluated. The air pressure P1 of the reference tire was 20 kPa. The ratio (P1 / P) is 0.04. Evaluation value S1 of this tire was measured. The evaluation value S1 was set as the reference value Sa.

  The rigidity feelings of the tires E1, E2 and E3 were evaluated by the rigidity evaluation method shown in FIGS. Evaluation values S1 of the tires E1, E2 and E3 were measured. These evaluation values S1 were compared with the reference value Sa of the reference tire to evaluate the feeling of rigidity. It was confirmed whether the evaluation results of the stiffness evaluation method and the sensory evaluation match.

  Furthermore, the air pressure P1 was set to 50 kPa, 70 kPa, 100 kPa, and 150 kPa, and it was confirmed whether the evaluation results of the stiffness evaluation method and the sensory evaluation match. The results are shown in Table 3.

[Test 4]
Three types of tires, tires E1, E2, and E3 used in Test 3, and a reference tire were prepared. These tires have already been evaluated for rigidity at the side wall (radial direction) by sensory evaluation. In this sensory evaluation, the judgment results of the tires E1 and E3 were good. The determination result of the tire E2 was poor. The determination result of this reference tire was good. In the sensory evaluation, it was evaluated that the rigidity of the reference tire was smaller than the rigidity of the tires E1 and E3 and greater than the rigidity of the tire E2.

  With the stiffness evaluation method shown in FIG. 3, the stiffness of the reference tire was evaluated. Evaluation value S2 of this tire was measured. The evaluation value S2 was set as the reference value Sb.

  The rigidity feeling of the tires E1, E2, and E3 was evaluated by the rigidity feeling evaluation method shown in FIG. Evaluation values S2 of the tires E1, E2, and E3 were measured. These evaluation values S2 were compared with the reference value Sb of the reference tire, and the sense of rigidity was evaluated. It was confirmed whether the evaluation results of the stiffness evaluation method and the sensory evaluation match.

  Furthermore, the air pressure P1 was set to 50 kPa, 70 kPa, 100 kPa, and 150 kPa, and it was confirmed whether the evaluation results of the stiffness evaluation method and the sensory evaluation match. The results are shown in Table 4.

[Test 5]
Three types of tires, tires E1, E2, and E3 used in Test 3, and a reference tire were prepared. In these tires, evaluation of the rigidity of the sidewall portion (axial direction) has already been performed by sensory evaluation. In this sensory evaluation, the judgment results of the tires E1 and E2 were good. The determination result of the tire E3 was poor. The determination result of this reference tire was good. In the sensory evaluation, it was evaluated that the rigidity feeling of the reference tire was smaller than the rigidity feeling of the tires E1 and E2, and larger than the rigidity feeling of the tire E3.

  With the stiffness evaluation method shown in FIGS. 4A and 4B, the stiffness of the reference tire was evaluated. Evaluation value S3 of this tire was measured. The evaluation value S3 was set as the reference value Sc.

  The rigidity feelings of the tires E1, E2, and E3 were evaluated by the rigidity feeling evaluation method shown in FIGS. 4 (a) and 4 (b). Evaluation values S3 of tires E1, E2 and E3 were measured. The evaluation value S3 was compared with the reference value Sc of the reference tire, and the rigidity feeling was evaluated. It was confirmed whether the evaluation results of the stiffness evaluation method and the sensory evaluation match. As a result, it was confirmed that the evaluation results of the rigidity feeling evaluation method and the sensory evaluation coincided.

  According to the stiffness value method of the present invention, the tire stiffness can be quantitatively evaluated. Conventionally, it is possible to objectively evaluate the rigidity feeling that has been relied on sensory evaluation. Thereby, development of the tire suitable for the buyer's preference which selects a tire can be made easy. From this evaluation result, the superiority of the present invention is clear.

DESCRIPTION OF SYMBOLS 2 ... Tire assembly 4 ... Deflection machine 6 ... Tire 8 ... Rim 10 ... Mount 12 ... Support body 14 ... Load load body 16 ... Pressing tool 18 ..Main body 20 ... Rod 22 ... Head 24 ... Support jig 26 ... Support jig 28 ... Base 30 ... Pressing part 32 ... Long hole 34 ... Tip 38 ... pin 40 ... stopper

Claims (10)

It has a measurement process that measures the spring constant of the tire,
In this measurement process, the support jig supporting the tire and the pressing tool pressed against the tire sandwich the tire,
A load is applied to the tire by this sandwiching, and the deformation amount δ of the tire from the state in which the load F1 is applied to the state in which the load F2 is applied to the tire is measured,
The spring constant from the load F1 to the load F2 is measured from the loads F1 and F2 and the deformation amount δ.
The ratio (F1 / F) between the load F1 and the normal load F of the tire is 0.10 or more,
The ratio of the load F2 and the normal load F (F2 / F) is Ri der 0.20 or less,
An assembly preparation process is provided prior to the above measurement process,
In this assembly preparation process, the regular rim of this tire is prepared,
This tire is built into a regular rim into a tire assembly,
In the assembly preparation step, the tire assembly is filled with air to obtain the air pressure P1,
The ratio of a normal internal pressure P of the air pressure P1 and the tire (P1 / P) is 0.30 Der Ru rigid feeling evaluation method of a tire below. In the measurement step, the regular rim is used as a support jig, and the regular rim and the pressing tool sandwich the tire in the radial direction.
The stiffness evaluation method according to claim 1, wherein a radial spring constant of the tire is measured. The rigidity evaluation method according to claim 1 or 2, wherein the ratio (P1 / P) is 0.08 or more. The stiffness evaluation method according to any one of claims 1 to 3, wherein in the assembly preparation step, the tire assembly is filled with air, and the pressure is reduced to the air pressure P1 after the air pressure exceeds the air pressure P1. . In the measuring step, the tip of the pressing tool is formed in a spherical shape,
The rigidity evaluation method according to any one of claims 1 to 4, wherein the spherical radius is set to 15 mm or more and 30 mm or less.   The rigidity evaluation method according to any one of claims 1 to 5, wherein in the measurement step, the pressing tool presses the center in the axial direction of the tread. In the measurement step, the pressing tool presses the position of the distance T in the axial direction from the equator plane with respect to the tread width Wt,
The rigidity evaluation method according to any one of claims 1 to 5, wherein a ratio (T / Wt) of the distance T to the tread width Wt is set to 0.40 or more and 0.45 or less. In the measurement process, the support jig and the pressing tool sandwich the tire in the axial direction,
This support jig supports one sidewall portion in the axial direction of the tire, and this pressing tool presses the other sidewall portion in the axial direction of the tire,
The rigidity evaluation method according to claim 1, wherein an axial spring constant of the tire is measured. One of the support jig and the pressing tool presses the position of the height H1 in the radial direction of the tire in the sidewall portion, and the ratio of the height H1 to the height H of the tire (H1 / H) is 0.6 or more and 0.8 or less,
The rigidity evaluation method according to claim 8, wherein the other of the support jig and the pressing tool is in contact with the position of the sidewall portion having the maximum axial width. Either one of the support jig and the pressing tool includes a base and a pressing portion, and the pressing portion is capable of changing the position in the radial direction of the tire with respect to the base.
The rigidity evaluation method according to claim 9, wherein the pressing portion presses the position of the height H1 in the radial direction of the tire.

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