Tire test method

Abstract

To provide a tire testing method which makes it easy to assess cut resistance of a sidewall of a tire at a specific position in a circumferential direction.SOLUTION: A tire testing method according to an embodiment involves running over a protrusion with a sidewall of a rotating tire, and comprises a runover step of rotating the tire mounted on a support axle of a testing machine on a table and having the tire run over the protrusion provided on the base to acquire data.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a tire test method.

Background Art

[0002] In pneumatic tires (hereinafter referred to as "tires"), there are few cases where a burst occurs starting from the sidewall. Therefore, conventionally, there has been little need to evaluate the cut resistance of the sidewall, and a test method for such evaluation has not been established. However, in recent years, there has been a need to evaluate the cut resistance of the sidewall for some tires including racing tires.

[0003] As a test method for the sidewall proposed in the past, there is a method of driving a test vehicle equipped with a tire and damaging the sidewall by crossing a protrusion on the road surface at a portion near the shoulder of the tread of the tire (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, there is a need to evaluate the cut resistance of the sidewall at a specific position in the circumferential direction of the tire. Also, when conducting a test of crossing a protrusion multiple times with the same tire, there is a need to cross the protrusion at the same position in the circumferential direction of the tire each time. Further, when comparing the cut resistance of a tire as a reference product and a tire as a test product, there is a need to cross the protrusion at the same characteristic portion.

[0006] Despite such needs, in the previously proposed methods described above, since the tire attached to the actual vehicle rides over the protrusion, it has been difficult to control the tire to hit the protrusion at a specific position.

[0007] The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for easily evaluating the cut resistance of the sidewall at a specific position in the circumferential direction of the tire.

Means for Solving the Problems

[0008] The tire test method according to the embodiment is a tire test method in which a tire rides over a protrusion on the sidewall of a rolling tire, and includes a crossing step of rolling the tire attached to the support shaft of the test machine on a table to cross the protrusion provided on the table and acquire data. Measure the time-series changes of the forces generated on the rotation axis of the tire in three directions: the traveling direction of the tire, the axial direction of the tire, and the direction orthogonal to both the traveling direction and the axial direction. Identify the timing at which the force in any of the three directions becomes maximum. For each of the three directions, obtain the difference between the force at the timing and the force in the time period before the tire rides over the protrusion as the difference at the timing, and obtain the resultant force from the differences at the timings in the three directions. Further, the tire test method according to an embodiment is a tire test method for rolling over a protrusion on the sidewall of a rolling tire. The method includes a rolling-over step of rolling the tire attached to the support shaft of a testing machine on a table to roll over the protrusion provided on the table and acquire data. Measure the time-series changes of the forces generated on the rotation axis of the tire in three directions: the traveling direction of the tire, the axial direction of the tire, and the direction orthogonal to both the traveling direction and the axial direction. For each of the three directions, obtain the change in the difference between the force when the tire is riding over the protrusion and the force in the time period before the tire rides over the protrusion, either as a time-series change in the difference or a change based on the moving distance, as the change in the difference based on the time-series change or the moving distance. From the changes in the differences based on the time-series change or the moving distance in the three directions, obtain the change in the resultant force either as a time-series change or a change based on the moving distance. Determine the energy based on the change in the resultant force either as a time-series change or a change based on the moving distance from the time when the tire starts to roll over the protrusion to the time when the resultant force becomes maximum. Further, the tire test method according to an embodiment is a tire test method for rolling over a protrusion on the sidewall of a rolling tire. The method includes a rolling-over step of rolling the tire attached to the support shaft of a testing machine on a table to roll over the protrusion provided on the table and acquire data. The method is characterized by repeatedly performing the rolling-over step a plurality of times while changing the height of the protrusion from low to high, and identifying the height of the protrusion when the tire is damaged. Further, the tire testing machine according to the embodiment includes a support shaft for rolling the tire, a table on which the tire rolls, and a measuring instrument for collecting data during the rolling of the tire. In the tire testing machine that rolls the tire attached to the support shaft on the table and acquires data by the measuring instrument, a protrusion is provided on the table, and during the rolling of the tire, the sidewall of the tire is controlled to overcome the protrusion. The measuring instrument is a measuring instrument that measures the time-series change of the force generated on the rotation axis of the tire in three directions: the traveling direction of the tire, the axial direction of the tire, and the direction orthogonal to the traveling direction and the axial direction. A processing unit specifies the timing at which the force in any one of the three directions becomes maximum, and for each of the three directions, obtains the difference between the force at the timing and the force in the time period before the tire rides on the protrusion as the difference at the timing, and the processing unit is characterized in that a resultant force is obtained from the differences at the timings in the three directions. Further, the tire testing machine according to the embodiment includes a support shaft for rolling the tire, a table on which the tire rolls, and a measuring instrument for collecting data during the rolling of the tire. In the tire testing machine that rolls the tire attached to the support shaft on the table and acquires data by the measuring instrument, a protrusion is provided on the table, and during the rolling of the tire, the sidewall of the tire is controlled to overcome the protrusion. The measuring instrument is a measuring instrument that measures the time-series change of the force generated on the rotation axis of the tire in three directions: the traveling direction of the tire, the axial direction of the tire, and the direction orthogonal to the traveling direction and the axial direction. A processing unit obtains, for each of the three directions, the change in the time-series change or the change due to the moving distance of the difference between the force when the tire rides on the protrusion and the force in the time period before the tire rides on the protrusion as the change in the time-series change or the change due to the moving distance of the difference. The processing unit obtains the change in the time-series change or the change due to the moving distance of the resultant force from the changes in the time-series change or the changes due to the moving distance of the differences in the three directions. The processing unit is characterized in that energy is obtained based on the change in the time-series change or the change due to the moving distance of the resultant force from the time point when the tire starts to overcome the protrusion to the time point when the resultant force becomes maximum.

Advantages of the Invention

[0009] According to the present embodiment, it is easy to evaluate the cut resistance of the sidewall at a specific position in the circumferential direction of the tire.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Mode for Carrying Out the Invention

[0011] The embodiments will be described with reference to the drawings. It should be noted that the embodiments described below are merely examples, and those appropriately modified without departing from the gist of the present invention are included in the scope of the present invention.

[0012] As shown in FIGS. 1 to 3, the tire testing machine 10 of the present embodiment includes a stand 11 on which a pneumatic tire (hereinafter referred to as "tire") T rolls, and a moving part 12 that moves on the stand 11. The stand 11 is long in one direction (the left-right direction in FIGS. 1 and 3), and its upper surface is a horizontal plane. A protrusion 20 protruding upward is fixed near the center in the longitudinal direction of the stand 11.

[0013] In the following description, the lower side of FIG. 3 is the front side, and the upper side is the back side. The protrusion 20 is near the front edge of the base 11.

[0014] The moving part 12 has a frame 13 forming a substantially rectangular parallelepiped, a lifting device 14 provided on the upper part of the frame 13, a driving device 15 that moves up and down when the lifting device 14 operates, and a support shaft 16 provided on the driving device 15. A tire T is attached to this support shaft 16.

[0015] As shown in FIGS. 2 and 3, a rail 17 extending in the same direction as the longitudinal direction of the base 11 is provided in contact with the base 11. The frame 13 rides on this rail 17 and is movable along the rail 17. The movement of the frame 13 is performed by the operation of a movement motor 18 (see FIG. 4). When the frame 13 moves along the rail 17, the entire moving part 12 moves along the rail 17. The driving device 15 and the support shaft 16 are arranged inside this frame 13.

[0016] The lifting device 14 is a device that integrally moves the driving device 15, the support shaft 16, and the tire T attached to the support shaft 16 up and down, and consists of a motor.

[0017] The driving device 15 has a built-in motor, and is configured such that the support shaft 16 rotates when the motor rotates. The support shaft 16 is a shaft extending in a direction orthogonal to the longitudinal direction of the base 11 and in a horizontal direction. A wheel W with a tire T attached is attached to this support shaft 16. The support shaft 16 is a rotating shaft that rotates together with the tire T and the wheel W. When the support shaft 16 and the tire T rotate, the traveling direction of the tire T is the longitudinal direction of the base 11 (the left-right direction in FIGS. 1 and 3).

[0018] By manual or the operation of the equipment built in the driving device 15, the support shaft 16 can move forward and backward in its axial direction (the longitudinal direction of the support shaft 16). When the support shaft 16 moves forward and backward, the position of the tire T on the base 11 (the position in the direction orthogonal to the longitudinal direction of the base 11) is adjusted.

[0019] A force sensor 31 (see FIG. 4) is provided on the support shaft 16. The force sensor 31 is a kind of measuring instrument and measures the force generated on the support shaft 16. The force sensor 31 can measure the time-series changes in the magnitudes of the forces in three orthogonal directions: the longitudinal force Fx, which is the force in the traveling direction of the tire T, the lateral force Fy, which is the force in the axial direction of the tire T, and the vertical force Fz. While the tire T is rolling while moving on the stand 11, the force sensor 31 continuously measures Fx, Fy, and Fz.

[0020] Also, a camera 32 as a photographing device is fixed to the frame 13. The camera 32 is a kind of measuring instrument and acquires video data. As shown in FIG. 2, the camera 32 is provided opposite to the disk of the wheel W at a location on the side opposite to the drive device 15 (i.e., the front side of the tire T) with the tire T in between. The photographing range of the camera 32 includes the contact portion of the tire T attached to the support shaft 16 with the stand 11. While the tire T is rolling while moving on the stand 11, the camera 32 continuously moves in the longitudinal direction of the stand 11 together with the frame 13 and the tire T, and continuously photographs the contact portion of the tire T with the stand 11 during the movement.

[0021] Note that a plurality of cameras may be provided on the frame 13. For example, in addition to the above camera 32, a camera for photographing the tire T from at least one of the front and rear in the traveling direction may be provided.

[0022] As shown in FIG. 4, a control processing device 30 is provided in the tire tester 10. Devices such as the lifting device 14, the drive device 15, and the moving motor 18, and measuring instruments such as the force sensor 31 and the camera 32 are connected to the control processing device 30. The control processing device 30 includes a control unit 33 and a processing unit 34.

[0023] The control unit 33 controls each device according to an instruction input by a tester. For example, the control unit 33 operates the lifting device 14 to change the height of the support shaft 16 from the base 11 and adjust the height of the tire T. Further, the control unit 33 operates the moving motor 18 to move the entire moving unit 12 in the longitudinal direction of the base 11 while rotating the support shaft 16 to rotate the tire T, thereby rolling the tire T on the base 11. Further, the processing unit 34 acquires data from measuring instruments such as the force sensor 31 and the camera 32 and performs calculations and the like. The tire test method described later is executed by controlling each device by the control unit 33 and the like.

[0024] A protrusion 20 is provided near the center in the longitudinal direction of the base 11. This protrusion 20 is for causing damage to the tire T. When the protrusion 20 has a sufficient height, when the tire T rolling on the base 11 crosses over the protrusion 20, the tire T is cut and damaged.

[0025] As shown in FIGS. 5 and 6, the protrusion 20 is a single plate-shaped member in which a plate-shaped portion 21 and a blade-shaped portion 22 are arranged side by side horizontally and integrally. The plate-shaped portion 21 is a thin rectangular parallelepiped, and the blade-shaped portion 22 has the same thickness and height as the plate-shaped portion 21 and the upper end is a blade sharpened upward. The cutting edge, which is the ridge of the blade-shaped portion 22, extends horizontally in the extension direction of the support shaft 16 (that is, the tire axis direction). Further, the cutting edge, which is the ridge of the blade-shaped portion 22, forms an acute angle in a cross section on a plane perpendicular to the tire axis direction.

[0026] As shown in FIG. 3, the protrusion 20 is provided at a location on the opposite side of the driving device 15 (that is, the front side of the tire T) with the tire T interposed therebetween. Further, the protrusion 20 is erected so as to be perpendicular to the traveling direction of the tire T. And the plate-shaped portion 21 is arranged close to the rail 17, and the blade-shaped portion 22 is arranged close to the center of the base 11. Since the blade-shaped portion 22 is closer to the center of the base 11, the tire T will cross over the blade-shaped portion 22 rather than the plate-shaped portion 21.

[0027] The protrusion 20 is sandwiched and fixed from both longitudinal sides of the base 11 by two fixing members 23. Each fixing member 23 is L-shaped in a cross-section perpendicular to the tire axis direction, and has a horizontal portion 24 and a vertical portion 25. The horizontal portion 24 is fixed to the base 11 with bolts or the like (not shown), and the vertical portion 25 presses the protrusion 20.

[0028] The height of the protrusion 20 varies. For example, it is set to be 50% or more and 80% or less of the cross-sectional height of the tire T during the test. The cross-sectional height of the tire T refers to the length in the tire diameter direction from the inner diameter surface to the outer diameter surface of the tire T, which is the height indicated by H in FIG. 7. The specific value of the height of the protrusion 20 depends on the tire T to be tested, but is, for example, 40 mm or more and 140 mm or less. Also, the thickness of the protrusion 20 varies, but is, for example, 3 mm or more and 20 mm or less.

[0029] Such a tire testing machine 10 is arranged in a test chamber in which the room temperature is maintained constant (for example, the room temperature is set to a predetermined temperature such as the standard state temperature for the test (for example, 25°C) or the temperature of the actual use environment of the tire T (if the tire T is used in a tropical region, the temperature in the tropical region; if the tire T is used in a cold region, the temperature in the cold region), etc., and is managed within a predetermined range of ±5°C or the like with respect to the set temperature). It is preferable that the humidity and air pressure in the test chamber are also managed.

[0030] Next, the tire T to be tested is shown in FIG. 7. Note that only half in the tire axis direction is shown in FIG. 7, and the actual tire T is symmetric about the tire center line C. The vertical direction in FIG. 7 is the tire diameter direction, the horizontal direction is the tire axis direction, and the direction perpendicular to the paper surface is the tire circumferential direction.

[0031] In the tire T, bead portions 9 are provided on both sides in the tire axis direction. The bead portion 9 includes a bead core 9a made of a steel wire wound in a circular shape, and a rubber bead filler 9b provided on the radially outer side of the bead core 9a.

[0032] One or more (e.g., two or three) carcass plies 2 are wound around the bead portions 9 on both axial sides of the tire. The carcass ply 2 is a sheet-like member in which a large number of ply cords arranged in a direction orthogonal to the tire circumferential direction are covered with rubber. The carcass ply 2 forms the skeletal shape of the tire T between the bead portions 9 on both axial sides of the tire, and wraps the bead portion 9 by being folded back and wound up from the inner side to the outer side in the tire axial direction around the bead portion 9. An inner liner 8 is provided inside the carcass ply 2. Also, a rubber chafer 3 is provided at a location on the outer side in the tire axial direction of the wound-up portion 2a of the carcass ply 2.

[0033] Also, one or more belts 4 are provided on the outer side in the tire radial direction of the carcass ply 2, and a belt reinforcing layer 5 is provided on the outer side in the tire radial direction of the belt 4. The belt 4 is a member formed by covering a large number of steel cords with rubber. The belt reinforcing layer 5 is a member formed by covering a large number of organic fiber cords with rubber. A tread rubber 6 is provided on the outer side in the tire radial direction of the belt reinforcing layer 5. A large number of grooves are provided in the tread rubber 6 to form a tread pattern.

[0034] Also, sidewall rubbers 7 are provided on both axial sides of the carcass ply 2. The tread rubber 6 and the sidewall rubber 7 overlap in the buttress, but either the tread rubber 6 or the sidewall rubber 7 may be on the tire surface side. In the buttress of FIG. 7, the tread rubber 6 is on the tire surface side. Although not shown, a wing rubber may be provided on the tire surface side at the boundary between the tread rubber 6 and the sidewall rubber 7. The portion of the sidewall rubber 7 on the inner side in the tire radial direction extends close to the bead portion 9 and covers a part of the rubber chafer 3.

[0035] Such a tire T is mounted on a wheel W. As shown in FIG. 8, the vicinity of the bead portion 9 of the tire T is in contact with the rim flange F of the rim of the wheel W. The end portion in the tire axial direction of the contact portion between the tire T and the rim flange F is at the position of the surface of the rubber chafer 3.

[0036] When the tire T crosses over the protrusion 20, it crosses over the protrusion 20 at at least one part of the sidewall of the tire T. The sidewall includes at least the sidewall rubber 7, and further includes a part of the tread rubber 6 (the part near the tire axial direction end), a part of the carcass ply 2, a part of the inner liner 8, a part or all of the bead filler 9b, a part or all of the rubber chafer 3, etc. An example of the range of the sidewall is shown by hatching in FIG. 8.

[0037] When the tire T crosses over the protrusion 20, it is not necessarily required to cross over the protrusion 20 with the entire sidewall, and it may cross over the protrusion 20 with only a part of the sidewall. Also, it may cross over the protrusion 20 in a wide area including the sidewall and the portions near it.

[0038] In any case, it is preferable to cross over the protrusion 20 so that the sidewall is cut from near the tire axial direction end of the tread rubber to near the outer end of the bead filler 9b in the tire radial direction.

[0039] By the way, as a result of the research by the inventor, it has become clear that damage to the sidewall of the tire T is likely to occur when a large shear stress acts in the tire radial direction. Based on FIG. 9 showing the positional relationship between the tire T and the protrusion 20, when crossing over the protrusion 20 at a portion outside the tire axial direction of the contact portion between the tire T and the rim flange F (the portion in the range indicated by the symbol S in the tire axial direction in FIG. 9), a shear stress in the tire radial direction (indicated by an arrow as the direction of the shear stress in FIG. 9) acts between the rim flange F and the protrusion 20, and it has become clear that damage to the sidewall is likely to occur.

[0040] Therefore, when the tire T crosses the protrusion 20, it is preferable that the tire T crosses the protrusion 20 at a portion axially outside the tire of the contact portion between the tire T and the rim flange F. In this case, the axial distance L (see FIG. 9) between the outer end in the tire axial direction of the contact portion between the tire T and the rim flange F and the tip of the protrusion 20 is preferably 4 mm or more and 6 mm or less. However, the distance L is not limited to this range. Also, L = 0 mm may be acceptable.

[0041] As shown in FIG. 10, the tire test method of the present embodiment includes a preparation step S1 of preparing for the test, an alignment step S2 of aligning the position of the portion of the tire T that is planned to cross the protrusion 20 with the protrusion 20 at the location of the protrusion 20, a movement step S3 of moving the tire T from the location of the protrusion 20 to a test start position that is one location in the longitudinal direction of the table 11, a crossing step S4 of starting to roll the tire T from the test start position and crossing the protrusion 20 with the tire T, and a calculation step S5 of performing calculations based on the data obtained in the crossing step S4.

[0042] In the preparation step S1, a predetermined internal pressure is applied to the tire T mounted on a predetermined rim. Here, the predetermined rim is the rim used when the tire T is mounted on an actual vehicle. Also, the predetermined internal pressure is the internal pressure applied when the tire T is mounted on an actual vehicle. However, when the vehicle on which the tire T is mounted is not determined, a standard rim is used as the predetermined rim, and a standard internal pressure is applied as the predetermined internal pressure. The tire T mounted on the rim and having the internal pressure applied is attached to the support shaft 16 together with the wheel W.

[0043] Note that the standard rim is the rim defined for each tire in the standard system on which the tire is based. For example, it is the standard rim in JATMA, and it is the "Measuring Rim" in TRA and ETRTO. Also, the standard internal pressure is the air pressure defined for each tire in the standard system on which the tire is based. In the case of truck and bus tires or light truck tires, it is the maximum air pressure in JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA, and "INFLATION PRESSURE" in ETRTO. Incidentally, the standard load is the "maximum load capacity" in JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA, or "LOAD CAPACITY" in ETRTO. However, when tire T is for passenger cars, usually 180 kPa is used instead of the above standard internal pressure, and when tire T is for passenger cars and is marked with "Extra Load" or "Reinforced" on tire T, 220 kPa is used instead of the above standard internal pressure.

[0044] In the next alignment step S2, as shown in FIG. 11, the tire T is supported by the support shaft 16 in a floating state in the air, and the rotation is adjusted so that the portion (hereinafter referred to as the "overcoming portion") that is planned to overcome the protrusion 20 of the tire T becomes the lowest point. In the adjusted state, as shown in FIGS. 11 and 12, the tire T is arranged on the protrusion 20. Thereby, the positions in the tire circumferential direction of the overcoming portion of the tire T and the protrusion 20 match. Note that the tire T is shown by a solid line in FIG. 11 and by a broken line in FIG. 12. At this time, it is arranged so that the distance L (see FIG. 9) in the tire axial direction between the outer end of the contact portion between the tire T and the rim flange F and the tip of the protrusion 20 becomes a desired length.

[0045] In the next moving step S3, first, the tire T moves a predetermined distance in the tire axial direction and toward the back side, and moves away from the position above the protrusion 20 (the movement of the tire T at this time is indicated by an arrow in FIG. 13). Next, the tire T lands on the base 11, and a predetermined load is applied to the tire T after landing. Next, the tire T moves while rolling from the position of the protrusion 20 to a test start position which is one position in the longitudinal direction of the base 11 (the movement of the tire T at this time is indicated by an arrow in FIG. 14).

[0046] When the tire T arrives at the test start position, the load is once removed from the tire T. Next, the tire T moves a distance of the above-mentioned predetermined distance in the tire axial direction and toward the front side (the movement of the tire T at this time is indicated by an arrow in FIG. 15). By this movement, the positional relationship in the tire axial direction between the tire T and the protrusion 20 returns to the positional relationship adjusted in the alignment step S2. Also, by this movement, the protrusion 20 overlaps the position in the traveling direction of the tire T. Next, a predetermined load is applied to the tire T. The predetermined load is the load applied to the tire T when actually mounted on a vehicle. However, when the vehicle on which the tire T is to be mounted is not determined, etc., the above-mentioned normal load is applied.

[0047] In the next crossing step S4, the tire T rolls and advances in the longitudinal direction on the base 11. The moving speed of the tire T is not limited, but is, for example, 0.3 to 0.4 km / h. During the movement, as shown in FIG. 16, the tire T crosses the protrusion 20. During the movement of the tire T, the force sensor 31 continuously measures the three-directional forces Fx, Fy, and Fz generated on the support shaft 16. Also, during the movement of the tire T, the camera 32 continuously photographs the contact portion of the tire T with the base 11. The data acquired by the force sensor 31 and the camera 32 is sent to the control processing device 30.

[0048] In the next calculation step S5, the processing unit 34 processes the measurement data of the force sensor 31. Here, it is assumed that damage D (see FIG. 16) in which the tire T bursts and the sidewall is cut occurs in the crossing step S4.

[0049] FIG. 17 is a diagram showing the time-series change of the force Fx measured by the force sensor 31. In FIG. 17, the horizontal axis represents the elapsed time from the start of the test, and the vertical axis represents the force Fx. It can be seen from FIG. 17 that the force Fx reaches the maximum value Fxmax at a certain point in time. The force Fxmax at this time is denoted as Fxb.

[0050] Diagrams showing similar time-series changes can also be obtained for Fy and Fz. Then, the forces Fy and Fz at the timing when the force Fx reaches the maximum value Fxmax are denoted as Fyb and Fzb. Note that since the timings at which the three-directional forces Fx, Fy, and Fz reach the maximum values Fxmax, Fymax, and Fzmax do not necessarily coincide, it is necessary to note that Fyb = Fymax and Fzb = Fzmax do not necessarily hold.

[0051] Alternatively, the maximum value Fymax of the axial force Fy of the tire T can be defined as the force Fyb, and the forces Fx and Fz at the timing when the force Fy reaches the maximum value Fymax can be defined as the forces Fxb and Fzb. Also, the maximum value Fzmax of the vertical force Fz can be defined as the force Fzb, and the forces Fx and Fy at the timing when the force Fz reaches the maximum value Fzmax can be defined as the forces Fxb and Fyb.

[0052] The forces Fxb, Fyb, and Fzb obtained in this way are values related to the forces when the tire T is damaged and can be used as indicators for evaluating the cut resistance of the sidewall of the tire T.

[0053] Furthermore, in the calculation step S5, the resultant force R is calculated by the processing unit 34. Specifically, the timing at which any one of the three directions of the traveling direction of the tire T, the axial direction of the tire T, and the vertical direction has the maximum force is specified, and for each of the three directions, the differences ΔFx, ΔFy, and ΔFz between the forces Fx, Fy, and Fz at that timing and the forces Fx, Fy, and Fz before the tire T rides on the protrusion 20 are calculated.

[0054] For example, the difference between the above Fxmax and the force Fx in the time period before the force Fx starts to increase in FIG. 17 (when there is variation in the force Fx in the time period, the average value of the force Fx in the time period) is ΔFx. Note that in the time period before the force Fx starts to increase, the tire T is not on the protrusion 20. Also, the difference between the force Fy at the timing when the force Fx reaches the maximum value Fxmax and the force Fy in the time period before the force Fy starts to increase (when there is variation in the force Fy in the time period, the average value of the force Fy in the time period) is ΔFy. ΔFz is obtained in the same way as ΔFy.

[0055] And the resultant force R is calculated by the following formula.

[0056]

Equation

[0057] The resultant force R obtained in this way is also a value related to the force when the tire T is damaged, and can be used as an index for evaluating the cut resistance of the sidewall of the tire T.

[0058] Furthermore, in the calculation step S5, in the processing unit 34, the energy E required for the tire T to be damaged is calculated. Specifically, first, for each of the three directions of the traveling direction, the axial direction, and the vertical direction of the tire T, the difference in the time series change between the forces Fx, Fy, Fz when the tire T is on the protrusion 20 and the forces Fx, Fy, Fz in the time period before the tire T gets on the protrusion 20 (when there is variation in the forces Fx, Fy, Fz in the time period, the average values of the forces Fx, Fy, Fz in the time period) is obtained as the "time series change of the difference ΔFx(t), ΔFy(t), ΔFz(t)".

[0059] Next, from the time series change of the difference ΔFx(t), ΔFy(t), ΔFz(t), the time series change of the resultant force R(t) is calculated by the following formula.

[0060]

Equation

[0061] Incidentally, the time when this resultant force R(t) reaches its maximum value is the time when the tire T bursts and damage occurs. Therefore, the maximum value of the resultant force R(t) can be used as an index for evaluating the cut resistance of the sidewall of the tire T.

[0062] Next, the time-series change R(t) of the resultant force is converted into the change R(l) according to the moving distance of the resultant force. Assuming the moving speed of the tire T is V (km / hour) and the time is t (seconds), the moving distance l (m) is obtained by the following formula.

[0063]

Equation

[0064] Using this formula, the change R(l) according to the moving distance of the resultant force is calculated by the following formula. The change R(l) according to the moving distance of the resultant force is shown in Fig. 18.

[0065]

Equation

[0066] The energy E required for the tire T to be damaged is calculated as the total value of the resultant force R(l) from the moving distance l1 when the change R(l) according to the moving distance of the resultant force starts to change (at this time, it can be interpreted that the tire T starts to ride on the protrusion 20) to the moving distance l2 when the change R(l) according to the moving distance of the resultant force reaches its peak (at this time, it can be interpreted that the tire T is damaged). The energy E, which is the total value, is obtained by the following integral calculation and corresponds to the area shaded in Fig. 18.

[0067]

Equation

[0068] Note that the conversion from data as a time series change to data as a change due to the moving distance may be performed at any timing. For example, first, the change in force as a time series change Fx(t), Fy(t), Fz(t) is converted to the change due to the moving distance Fx(l), Fy(l), Fz(l). For the three directions, the forces Fx(l), Fy(l), Fz(l) when the tire T is on the protrusion 20 and the forces Fx(l), Fy(l), Fz(l) before the tire T gets on the protrusion 20 (when there are variations in the forces Fx(l), Fy(l), Fz(l) at the location before the tire T gets on the protrusion 20, the average value of the forces Fx(l), Fy(l), Fz(l) at the location) The change due to the moving distance of the difference from is obtained as "the change due to the moving distance of the difference ΔFx(l), ΔFy(l), ΔFz(l)". Then, from the "change due to the moving distance of the difference ΔFx(l), ΔFy(l), ΔFz(l)" in the three directions, the change due to the moving distance of the resultant force R(l) is obtained, and the energy E is obtained in the same manner as above.

[0069] The above test steps S1 to S5 are performed on a plurality of types of tires T. Here, in each test, it is controlled so that the protrusion 20 hits a specific position in the tire circumferential direction (for example, the position of a specific block). Then, for each tire T, at least any one of the maximum values of the forces Fxb, Fyb, Fzb, the resultant force R, the resultant force R(t), and the energy E is calculated. Then, based on the magnitudes of these values, the superiority or inferiority of the cut resistance of the plurality of types of tires T is evaluated. Also, between the tire T as a reference product and the tire T as a prototype, at least any one of the forces Fxb, Fyb, Fzb, the resultant force R, the maximum value of the resultant force R(t), and the energy E is compared, and the quality of the prototype is evaluated.

[0070] Also, the state in which the tire T is damaged can be confirmed from the video taken by the camera 32.

[0071] Incidentally, in the description of the above calculation step S5, it was assumed that the tire T was damaged during the crossing step S4. However, when the protrusion 20 is low, no damage occurs. Therefore, steps S1 to S4 may be repeated a plurality of times while gradually changing the height of the protrusion 20 from low to high until damage occurs to the sidewall.

[0072] Specifically, first, the lowest protrusion 20 is fixed to the base 11, and the first steps S1 to S4 are performed. As the lowest protrusion 20, for example, those having a height of 45% or more and 55% or less of the section height of the tire T during the test, or those lower than that, are adopted.

[0073] And when no damage occurs to the sidewall (damage means damage that impairs the function of the tire T such as the sidewall being cut, and does not include damage of a minor degree), a protrusion 20 higher than that in the first time is fixed to the base 11, and the second steps S1 to S4 are performed.

[0074] The second steps S1 to S4 may be performed using the same tire T as in the first steps S1 to S4, or may be performed after replacing the test target tire T with a new one. When the first and second tests (steps S1 to S4) are performed using the same tire T, in the second test, it is preferable to adjust so that the protrusion 20 hits a position different from that in the first test and having the same characteristics as that in the first test (for example, the position of the block having the same shape as that in the first test). In this way, steps S1 to S4 are repeated until damage occurs to the sidewall. And when damage occurs to the sidewall, the height of the protrusion 20 at that time is recorded, and the test of that tire T is completed.

[0075] Tests to change the height of the protrusion 20 are carried out for multiple types of tires T. Then, since the height of the protrusion 20 when damage occurs on the sidewall is different for each tire T, the superiority or inferiority of the cut resistance of the tire T is evaluated based on this difference. Also, the height of the protrusion 20 when damage occurs on the sidewall is specified for the tire T as a reference product and the tire T as a prototype, and a determination of the quality of the prototype relative to the reference product is made.

[0076] As described above, in the tire test method of the present embodiment, it includes a crossing step of rolling the tire T attached to the support shaft 16 of the tire testing machine 10 on the base 11 and crossing the protrusion 20 provided on the base 11 with the tire T to acquire data. According to this method, unlike the case of an actual vehicle test, since the protrusion 20 can be pinpointed at a specific position of the tire T, the cut resistance of the sidewall at a specific position in the tire circumferential direction can be evaluated.

[0077] Therefore, when conducting a test of crossing the protrusion 20 multiple times with the same tire T, each time, it is possible to cross the protrusion 20 at the same position in the circumferential direction of the tire T or at a position having the same characteristics. Also, when comparing the cut resistance of the tire T as a reference product and the tire T as a prototype, it is also possible to cross the protrusion 20 at the same characteristic part.

[0078] Here, before the crossing step S4, an alignment step S2 is executed in which the tire T is placed at the location of the protrusion 20 to align the position of the part of the tire T that is planned to cross the protrusion 20 with the protrusion 20. Next, a moving step S3 is executed in which the tire T is rolled and moved from the location of the protrusion 20 to a test start position, which is one location in the longitudinal direction of the base 11. Then, the crossing step S4 is executed after the moving step S3. Since the alignment step S2 and the moving step S3 are executed before the crossing step S4 in this way, the protrusion 20 can be pinpointed at a specific position of the tire T.

[0079] Also, as described above, in the crossing step S4, since the protrusion 20 is crossed at a portion outside the contact portion between the tire T and the rim flange F in the tire axial direction, the sidewall of the tire T is likely to be damaged.

[0080] Also, as described above, in the crossing step S4, the camera 32 that moves integrally with the tire T photographs the tire T when crossing the protrusion 20, so that the damage to the tire T can be observed in time series.

[0081] Also, as described above, in the crossing step S4, the time-series changes of the forces Fx, Fy, and Fz generated on the rotation axis (support shaft 16) of the tire T in three directions, namely, the traveling direction of the tire T, the axial direction of the tire T, and the vertical direction orthogonal to the traveling direction and the axial direction, are measured. Therefore, the peak values of the time-series changes of the forces Fx, Fy, and Fz in each direction can be used to evaluate the cut resistance of the tire T.

[0082] Also, as described above, since the resultant force R is calculated based on the measured forces Fx, Fy, and Fz, the cut resistance of the tire T can be evaluated based on the resultant force R. Also, as described above, since the energy E is calculated based on the time-series change or the change according to the moving distance of the resultant force R, the cut resistance of the tire T can be evaluated based on the energy E.

[0083] Also, as described above, by repeatedly performing the crossing step S4 while changing the height of the protrusion 20 from low to high, the height of the protrusion 20 when the tire T is damaged can be specified. And the cut resistance of the tire T can be evaluated based on the height of the protrusion 20 when the tire T is damaged.

[0084] Various changes can be made to the above embodiments.

[0085] For example, as the protrusion, those with various shapes protruding upward from the upper surface of the base 11 can be adopted. The protrusion 120 in FIG. 19 is formed by stacking a plurality of (six in the figure) plates 120a with different heights. The plurality of plates 120a overlap in the longitudinal direction of the base 11. The height of the plate 120a increases as it goes in one direction of the longitudinal direction of the base 11, and the whole of the plurality of plates 120a has the shape of a blade having a tip at the said one side.

Explanation of Signs

[0086] C… Tire center line, F… Rim flange, T… Tire, W… Wheel, 2… Carcass ply, 2a… Wrapped-up part, 3… Rubber chafer, 4… Belt, 5… Belt reinforcing layer, 6… Tread rubber, 7… Sidewall rubber, 8… Inner liner, 9… Bead part, 9a… Bead core, 9b… Bead filler, 10… Tire tester, 11… Base, 12… Moving part, 13… Frame, 14… Lifting device, 15… Driving device, 16… Support shaft, 17… Rail, 18… Moving motor, 20… Protrusion, 21… Plate-like part, 22… Blade-shaped part, 23… Fixing member, 24… Horizontal part, 25… Vertical part, 30… Control processing device, 31… Force sensor, 32… Camera, 33… Control unit, 34… Processing unit, 120… Protrusion, 120a… Plate

Claims

1. In a tire test method for rolling over a protrusion on the sidewall of a rolling tire, it includes a rolling-over step of rolling the tire attached to the support shaft of a testing machine on a platform to roll over the protrusion provided on the platform and acquire data, measuring the time-series change of the force generated on the rotation axis of the tire in three directions: the traveling direction of the tire, the axial direction of the tire, and the direction orthogonal to both the traveling direction and the axial direction, identifying the timing at which the force in any one of the three directions becomes maximum, and for each of the three directions, obtaining the difference between the force at the timing and the force in the time period before the tire rides over the protrusion as the difference at the timing, A tire test method, characterized in that a resultant force is obtained from the differences at the timings in the three directions.

2. In a tire test method for rolling over a protrusion on the sidewall of a rolling tire, it includes a rolling-over step of rolling the tire attached to the support shaft of a testing machine on a platform to roll over the protrusion provided on the platform and acquire data, measuring the time-series change of the force generated on the rotation axis of the tire in three directions: the traveling direction of the tire, the axial direction of the tire, and the direction orthogonal to both the traveling direction and the axial direction, for each of the three directions, obtaining the change in the difference between the force when the tire is riding over the protrusion and the force in the time period before the tire rides over the protrusion, either as a time-series change or a change based on the moving distance, as the change in the difference either as a time-series change or a change based on the moving distance, obtaining the change in the resultant force either as a time-series change or a change based on the moving distance from the changes in the differences either as a time-series change or a change based on the moving distance in the three directions, A tire test method, characterized in that energy is obtained based on the change in the resultant force either as a time-series change or a change based on the moving distance from the time when the tire starts to roll over the protrusion to the time when the resultant force becomes maximum.

3. In a tire test method for rolling over a protrusion on the sidewall of a rolling tire, it includes a rolling-over step of rolling the tire attached to the support shaft of a testing machine on a platform to roll over the protrusion provided on the platform and acquire data, A tire test method, characterized in that the rolling-over step is executed multiple times while changing the height of the protrusion from low to high, and the height of the protrusion when the tire is damaged is identified.

4. A positioning step of placing the tire at the location of the protrusion and aligning the position in the tire circumferential direction between a portion of the tire expected to cross over the protrusion and the protrusion; A moving step of rolling and moving the tire from the location of the protrusion to a test start position which is one location in the longitudinal direction of the table, and including: The tire test method according to any one of claims 1 to 3, wherein in the crossing-over step, the tire is started to be rolled from the test start position to cross over the protrusion.

5. The tire is attached to a wheel having a rim flange, The tire test method according to any one of claims 1 to 4, wherein the protrusion is crossed over at a portion of the tire axially outside of the contact portion between the tire and the rim flange.

6. The tire test method according to any one of claims 1 to 5, wherein the tire is photographed by a camera that moves integrally with the tire when crossing over the protrusion.

7. A tire testing machine having a support shaft for rolling the tire, a table on which the tire rolls, and a measuring device for collecting data during the rolling of the tire, and rolling the tire attached to the support shaft on the table to acquire data by the measuring device, A protrusion is provided on the table, and during the rolling of the tire, the sidewall of the tire is controlled to cross over the protrusion, The measuring device is a measuring device that measures the time-series change of the force generated on the rotation axis of the tire in three directions: the traveling direction of the tire, the axial direction of the tire, and the direction orthogonal to the traveling direction and the axial direction, The processing unit specifies the timing at which the force in any one of the three directions becomes maximum, and for each of the three directions, obtains the difference between the force at the timing and the force in the time period before the tire rides on the protrusion as the difference at the timing, The tire testing machine is characterized in that the processing unit obtains the resultant force from the differences at the timings in the three directions.

8. A tire testing machine having a support shaft for rolling the tire, a table on which the tire rolls, and a measuring device for collecting data during the rolling of the tire, and rolling the tire attached to the support shaft on the table to acquire data by the measuring device, A protrusion is provided on the table, and during the rolling of the tire, the sidewall of the tire is controlled to cross over the protrusion, The measuring device is a measuring device that measures the time-series change of the force generated on the rotation axis of the tire in three directions: the traveling direction of the tire, the axial direction of the tire, and the direction orthogonal to the traveling direction and the axial direction. For each of the three directions, the processing unit obtains the time-series change of the difference between the force when the tire is on the protrusion and the force in the time period before the tire gets on the protrusion, or the change due to the moving distance, as the time-series change of the difference or the change due to the moving distance. The processing unit obtains the time-series change of the resultant force or the change due to the moving distance of the resultant force from the time-series change of the difference or the change due to the moving distance in the three directions. The tire testing machine is characterized in that the processing unit obtains energy based on the time-series change of the resultant force or the change due to the moving distance of the resultant force from the time when the tire starts to cross the protrusion to the time when the resultant force becomes maximum.

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