JP2020060479A - Tire testing method - Google Patents

Abstract

To provide a testing method for a tire 2, in which a side cut can be repeatedly reproduced in a state that is close to a side cut state confirmed during actual traveling, in order to properly evaluate cut-resistance of the tire 2.SOLUTION: The testing method applies a testing device 42 in which a support shaft 54 supporting a tire 2 is moved toward a floor surface 56 where a protrusion 44 is disposed, so that the protrusion 44 is pressed against the tire 2, in order to evaluate cut-resistance of a side part S of the tire 2. The testing method includes: (1) a step of setting the tire 2 relative to the protrusion 44 such that a tip 58 of the protrusion 44 contacts a shoulder part Sh of the tire 2; and (2) a step of bringing the support shaft 54 and the floor surface 56 close to each other in order to press the protrusion 44 against the tire 2. The tip 58 of the protrusion 44 is pointed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a tire testing method. In particular, the present invention relates to a test method for evaluating the cut resistance of tire side parts.

  For example, in a tire traveling on an uneven terrain, the tire may slip off a rock or the like to cause a cut-like damage (hereinafter also referred to as a side cut) in a side portion of the tire. Since the damage caused to the tire including this side cut affects the durability, the tire is evaluated for resistance to damage.

  As a test method for evaluating resistance to damage, a test method of actually running a vehicle to reproduce damage (also referred to as an actual vehicle durability test) and, for example, a test method disclosed in Patent Document 1 A test method for reproducing damage in an apparatus (also called a bench test) is known.

JP, 2018-004577, A

  In the evaluation of tire side cut resistance, that is, cut resistance, an actual vehicle durability test and a bench test are also considered.

  In the actual vehicle endurance test, the vehicle is run to intentionally slide the tire off the rock, causing a side cut on the tire. In this actual vehicle durability test, the results may change depending on the shape of the target rock and how the tire is brought into contact with the rock. In particular, it is difficult to repeatedly generate the same side cut because the way of contacting the rock with the tire depends on the handling of the driver.

  As a bench test in the evaluation of cut resistance, a method of causing damage by hitting a blade against a buttress of a tire in the manner of a pendulum (hereinafter referred to as a pendulum test) is known. This pendulum test does not reproduce the movement of the tire with respect to the rock when the tire traveling on rough terrain slides off the rock. Tire movements are not reflected. Therefore, in this pendulum test, although a side cut can be generated in the side portion, the side cut state is different from the side cut state confirmed in actual traveling.

  Under the circumstances described above, it is necessary to establish a test method that can repeatedly reproduce the sidecut in a state close to the state of the sidecut confirmed in actual running and can appropriately evaluate the cut resistance of the tire. Has been.

  The present invention has been made in view of such actual circumstances, and it is possible to repeatedly reproduce a side cut in a state close to the state of the side cut confirmed in actual running, and to appropriately evaluate the cut resistance of the tire. It is an object of the present invention to provide a tire testing method capable of

A preferred tire testing method according to the present invention is a support shaft that supports a tire, and a test device configured to press the protrusion against the tire by moving the protrusion toward a floor surface on which the protrusion is installed. Using a test method for evaluating the cut resistance of the side portion of the tire,
(1) a step of setting the tire with respect to the protrusion so that a tip portion of the protrusion comes into contact with a shoulder portion of the tire;
(2) A step of bringing the support shaft and the floor surface close to each other and pressing the protrusion against the tire, and a tip portion of the protrusion is sharp.

  Preferably, in this tire testing method, the tire includes a belt laminated with a carcass on the inner side in the radial direction of the tread, and the belt includes a plurality of layers laminated in the radial direction. In this test method, in the step of setting the tire with respect to the protrusion, the tip end portion of the protrusion has a shaft more than the end of the outermost layer in the radial direction among the plurality of layers forming the belt. The tire is set to the protrusion so as to be located outside in the direction.

  More preferably, in the tire testing method, the distance from the outer end of the tire in the axial direction is from a position corresponding to 20% of the half of the sectional width of the tire to the outer end of the tire. The tire is set with respect to the protrusion such that the tip end portion of the protrusion is located in the zone.

  Preferably, in this tire testing method, the tip end portion of the protrusion has a ridge line extending in the axial direction of the tire set in the test device in a plan view of the protrusion, and a pair of slopes extending on both sides of the ridge line. Have. In the cross section of the protrusion along the plane parallel to the equatorial plane of the tire, the angle formed by the pair of slopes is an acute angle.

  Preferably, in this tire testing method, the height of the protrusion from the floor surface is higher than the sectional height of the tire set in the testing device.

  Preferably, in this tire testing method, the moving speed of the support shaft with respect to the floor surface is 50 mm / min or more and 150 mm / min or less.

  In the tire testing method according to the present invention, the distance between the support shaft and the floor surface is shortened, and the shoulder portion of the tire comes into contact with the tip end portion of the protrusion, whereby a load acts on the shoulder portion and the shoulder portion is deformed. To do. The shoulder part is pushed up by the protrusion and eventually slides down from the tip of the protrusion. Since the tips of the protrusions are sharp, the shoulder portion slides down from the tips, causing a side cut in the tire.

  In this test method, the contact position between the tire and the protrusion moves from the shoulder portion to the side portion by sliding the tire off the tip portion of the protrusion. The movement of the tire with respect to the protrusion in this test method is close to the movement of the tire with respect to the rock when the tire traveling on an uneven terrain slides off the rock, although the tire does not rotate. The side-cut state generated on the tire by this test method is close to the side-cut state confirmed in actual running.

  This test method can repeatedly reproduce a side cut in a state close to the state of the side cut confirmed in actual running, and can appropriately evaluate the cut resistance of the tire.

FIG. 1 is a cross-sectional view showing an example of a pneumatic tire used in a test method according to an embodiment of the present invention. FIG. 2 is a front view schematically showing an example of a test apparatus used for a tire testing method. FIG. 3 is an explanatory diagram illustrating the protrusions provided on the test apparatus. FIG. 4 is a sectional view taken along line IV-IV of FIG. FIG. 5: is explanatory drawing explaining the position of the tire with respect to a protrusion. FIG. 6 is a graph showing the relationship between load and displacement. FIG. 7: is a figure which shows the modification of a protrusion. FIG. 8 is a diagram showing another modification of the protrusion.

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

  In the present invention, a state in which a tire is incorporated into a regular rim, the internal pressure of the tire is adjusted to the regular internal pressure, and no load is applied to this tire is called a regular state. In the present invention, unless otherwise specified, the dimensions and angles of the tire and each part of the tire are measured under normal conditions.

  In the present invention, the regular rim means a rim defined in the standard on which the tire depends. “Standard rim” in JATMA standard, “Design Rim” in TRA standard, and “Measuring Rim” in ETRTO standard are regular rims.

  In the present invention, the normal internal pressure means the internal pressure defined in the standard on which the tire depends. "Maximum value" published in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in JATMA standard, "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA standard, and "INFLATION PRESSURE" in ETRTO standard are normal internal pressures.

  In the present invention, the normal load means a load defined in the standard on which the tire depends. "Maximum load capacity" in JATMA standard, "Maximum value" published in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA standard, and "LOAD CAPACITY" in ETRTO standard are normal loads.

[tire]
FIG. 1 shows an example of a pneumatic tire 2 (hereinafter, may be simply referred to as “tire 2”) used in a test method according to an embodiment of the present invention. The tire 2 is mounted on a vehicle such as a passenger car, for example, an SUV (sport utility vehicle).

  FIG. 1 shows a part of a cross section of the tire 2 along a plane including the rotation axis of the tire 2. In FIG. 1, the vertical direction is the radial direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. In FIG. 1, the alternate long and short dash line CL is the equatorial plane of the tire 2.

  In FIG. 1, the tire 2 is incorporated in the rim R. The inside of the tire 2 is filled with air, and the internal pressure of the tire 2 is adjusted to the normal internal pressure. In FIG. 1, the tire 2 is not loaded.

  In FIG. 1, reference numeral PW is an axial outer end of the tire 2. The outer end PW is specified based on a virtual side surface obtained by assuming that the side surface of the tire 2 has no decoration such as a pattern or a character. The axial distance from one outer end PW to the other outer end PW is the maximum width of the tire 2, that is, the sectional width of the tire 2 (see JATMA, etc.).

  The tire 2 includes a tread 4, a pair of sidewalls 6, a pair of clinches 8, a pair of beads 10, a pair of chafers 12, a carcass 14, an inner liner 16, a belt 18 and a band 20.

  The outer peripheral surface of the tread 4 is a tread surface 22. The tire 2 contacts the road surface at the tread surface 22. In this tire 2, the tread 4 includes a base portion 24 and a cap portion 26 located radially outside the base portion 24. The base portion 24 is made of a crosslinked rubber in consideration of adhesiveness. The cap portion 26 is made of a crosslinked rubber in consideration of wear resistance and grip performance.

  Each sidewall 6 is located radially inward of the end of the tread 4. The side wall 6 is made of a crosslinked rubber in which cut resistance is taken into consideration. In this tire 2, a wing 28 is provided between the sidewall 6 and the tread 4. The wing 28 is made of a crosslinked rubber in consideration of adhesiveness.

  Each clinch 8 is located inside the sidewall 6 in the radial direction. As shown in FIG. 1, a part of the clinch 8 contacts the flange Fg of the rim R. The clinch 8 is made of a crosslinked rubber in consideration of wear resistance.

  Each bead 10 is located inside the clinch 8 in the axial direction. The bead 10 includes a core 30 and an apex 32. The core 30 includes a wire made of steel. In the cross section of the tire 2 shown in FIG. 1, the apex 32 is tapered outward in the radial direction. The apex 32 is made of crosslinked rubber having high rigidity.

  Each chafer 12 is located inside the bead 10 in the radial direction. As shown in FIG. 1, at least a part of the chafer 12 contacts the seat St of the rim R. In the tire 2, the chafer 12 is made of cloth and rubber impregnated in the cloth.

  The carcass 14 is located inside the tread 4, the pair of sidewalls 6, and the pair of clinch 8. The carcass 14 extends from one bead 10 toward the other bead 10. The carcass 14 includes at least one carcass ply 34. The carcass 14 of the tire 2 is composed of two carcass plies 34. The carcass 14 of the tire 2 has a radial structure.

  Although not shown, the carcass ply 34 includes a number of carcass cords arranged in parallel. In the tire 2, cords made of organic fibers are used as carcass cords. Examples of the organic fiber include nylon fiber, polyester fiber, rayon fiber and aramid fiber.

  The inner liner 16 is located inside the carcass 14. The inner liner 16 constitutes the inner surface of the tire 2. The inner liner 16 is made of a crosslinked rubber having an excellent air shielding property.

  The belt 18 is laminated on the carcass 14 inside the tread 4 in the radial direction. The belt 18 is located radially inside the band 20. In FIG. 1, a double-headed arrow BW indicates the width of the belt 18.

  In the tire 2, in the axial direction, the width BW of the belt 18 is set within the range of 0.70 times or more and 0.95 times or less of the sectional width.

  In the tire 2, the belt 18 is composed of a plurality of layers 36 laminated in the radial direction. As shown in FIG. 1, the belt 18 of the tire 2 is composed of two layers 36. In the tire 2, of the two layers 36, the layer 36a located on the inner side in the radial direction is referred to as the inner layer 36a, and the layer 36b located on the outer side is also referred to as the outer layer 36b.

  Although not shown, each of the inner layer 36a and the outer layer 36b includes a number of belt cords arranged in parallel. Each belt cord is inclined with respect to the equatorial plane. In this tire 2, the material of the belt cord is steel.

  In this tire 2, as shown in FIG. 1, the width of the outer layer 36b is narrower than the width of the inner layer 36a in the axial direction. The width of the outer layer 36b is set in the range of 0.85 times to 0.98 times the width of the inner layer 36a. In the tire 2, the width of the inner layer 36a is the width BW of the belt 18 described above.

  The band 20 is located inside the tread 4 in the radial direction. The band 20 is located between the tread 4 and the belt 18 in the radial direction. The band 20 of the tire 2 has a full band 20F that covers the entire belt 18 and a pair of edge bands 20E that covers the end portions of the belt 18.

  The band 20 includes a band cord that is spirally wound. The band cord is made of organic fiber. Examples of the organic fiber include nylon fiber, polyester fiber, rayon fiber and aramid fiber.

  In the tire 2, the equatorial plane portion of the tread 4 is the center portion C. The end portion of the tread 4 is a shoulder portion Sh. The middle portion M is between the center portion C and the shoulder portion Sh.

  As shown in FIG. 1, in this tire 2, a plurality of vertical grooves 38 are formed in the tread 4. These vertical grooves 38 are juxtaposed in the axial direction. Each vertical groove 38 extends in the circumferential direction. In this tire 2, five land portions 40 are formed by carving four vertical grooves 38. These land parts 40 are juxtaposed in the axial direction.

  In the tire 2, among the four vertical grooves 38, the vertical groove 38c located inside in the axial direction is also referred to as a center vertical groove 38c, and the vertical groove 38s located outside in the axial direction is also referred to as a side vertical groove 38s. To be done. In this tire 2, the portion from one center vertical groove 38c to the other center vertical groove 38c is the above-mentioned center portion C. The portion from the center vertical groove 38c to the side vertical groove 38s is the above-mentioned middle portion M. An outer portion of the side vertical groove 38s in the axial direction is the shoulder portion Sh described above.

  In the tire 2, the side wall 6 and the clinch 8 that are continuous with the shoulder Sh are the side S. The side portion S extends radially inward from the shoulder portion Sh. A boundary portion between the shoulder portion Sh and the side portion S is also referred to as a buttress B.

[Test equipment]
FIG. 2 shows an example of the test apparatus 42 used in the test method according to the embodiment of the present invention. In this test method, the test apparatus 42 shown in FIG. 2 is used to evaluate the cut resistance of the side portion S of the tire 2.

  The test device 42 is a compression tester including a predetermined protrusion 44. As shown in FIG. 2, the tire 2 is set in the test device 42. In FIG. 2, the vertical direction is the height direction of the test apparatus 42. This height direction corresponds to the radial direction of the tire 2. The left-right direction is the width direction of the test device 42. This width direction corresponds to the axial direction of the tire 2. The front side of this paper surface is the front side of the test apparatus 42.

  The test device 42 includes a base member 46, a top plate 48, a pair of slide bars 50, a pair of vertical moving portions 52, and a support shaft 54.

  In the test device 42, the left and right slide bars 50 extend in the height direction between the base member 46 and the top plate 48. A vertical movement unit 52 is supported by each slide bar 50. Although not shown, the test device 42 includes a vertical drive unit that moves the vertical movement unit 52 in the height direction. In this test device 42, the left and right slide bars 50 are rotated by the vertical drive unit, and the vertical movement unit 52 is moved in the height direction by the rotation of the slide bar 50. The moving speed of the vertical moving unit 52 is controlled by the rotating speed of the slide bar 50. Depending on the direction of rotation of the slide bar 50, the ascent and descent of the vertical movement unit 52 is controlled.

  In the test device 42, the support shaft 54 extends in the width direction. The support shaft 54 is supported between the left and right vertical movement parts 52. In the test device 42, the tire 2 incorporated in the rim R is supported by the support shaft 54.

  In this test device 42, when the vertical movement unit 52 is lowered, the support shaft 54 moves toward the floor surface 56 of the base member 46. In this test device 42, when the support shaft 54 is moved toward the floor surface 56, the tire 2 is lowered.

  In this test method, a compression tester generally used in performance evaluation of the tire 2 is used as the test device 42. Although not shown, the test device 42 is provided with a load detector that detects a load acting on the tire 2 and a displacement gauge that detects a moving distance of the support shaft 54, that is, a displacement of the support shaft 54. The test device 42 further includes a processing unit (not shown) that processes the detection signals output from the load detector and the displacement meter, and outputs a displacement-load curve described later, for example. This processing means is composed of, for example, a microcomputer including a CPU and a memory.

  In this test apparatus 42, as shown in FIG. 2, the protrusion 44 is installed on the floor surface 56. The protrusion 44 is fixed to the floor surface 56 by a fixing means (not shown). Although not described in detail, in this test device 42, the position of the protrusion 44 in the width direction and the front-rear direction on the floor surface 56 can be finely adjusted.

  FIG. 3 is a plan view showing a part of the floor surface 56 on which the protrusion 44 is installed. In FIG. 3, the left-right direction is the width direction of the test apparatus 42, and the up-down direction is the front-back direction of the test apparatus 42. In FIG. 3, the lower side of this paper is the front side of the test apparatus 42. The direction perpendicular to the paper surface is the height direction of the test device 42. In FIG. 3, the thin solid line AL is the rotation axis of the tire 2 set in the test device 42.

  FIG. 4 shows a cross section of the protrusion 44 taken along line IV-IV of FIG. In FIG. 4, the left-right direction is the front-back direction of the test apparatus 42. In FIG. 4, the right side of the drawing is the front side of the test apparatus 42. In FIG. 4, the vertical direction is the height direction of the test apparatus 42. The direction perpendicular to the paper surface is the width direction of the test device 42.

  The IV-IV line in FIG. 3 is parallel to the equatorial plane of the tire 2 mounted on the test apparatus 42. The cross section of the protrusion 44 shown in FIG. 4 is a cross section of the protrusion 44 taken along a plane parallel to the equatorial plane of the tire 2 mounted on the test apparatus 42.

  In this test device 42, the tip portion 58 of the protrusion 44 is tapered upward in the height direction. This tip 58 is sharp. In the testing device 42, the tip portion 58 has a ridge line 60 and a pair of slopes 62 that spread on both sides of the ridge line 60.

  As shown in FIG. 3, the ridgeline 60 extends in the width direction of the test apparatus 42 in the plan view of the protrusion 44. As described above, the width direction of the test device 42 corresponds to the axial direction of the tire 2 set in the test device 42. In the test device 42, the ridgeline 60 of the protrusion 44 extends in the axial direction of the tire 2 set in the test device 42 in a plan view of the protrusion 44. As shown in FIG. 2, the ridgeline 60 of the protrusion 44 is parallel to the floor surface 56.

  One slope 62 extends rearward from the ridge 60. The other slope 62 extends from the ridgeline 60 to the front side. As shown in FIG. 4, the distance between the one slope 62 and the other slope 62 gradually increases downward from the ridgeline 60. In FIG. 4, reference numeral θ is an angle formed by one slope 62 and the other slope 62. In this test device 42, the angle θ is an acute angle.

[Test method]
Next, a test method according to the embodiment of the present invention will be described. This test method includes a preparation step and a measurement step.

  In the preparation process, the tire 2 is incorporated into the rim R. In this test method, the rim R is for testing. This rim R corresponds to a regular rim. The inside of the tire 2 is filled with air. As a result, the internal pressure of the tire 2 is adjusted to the regular internal pressure. The tire 2 incorporated in the rim R and having the internal pressure adjusted is attached to the support shaft 54 of the test apparatus 42. As a result, the tire 2 is supported by the support shaft 54.

  In the preparation step, the position of the protrusion 44 with respect to the tire 2 is further adjusted. In this test method, in this preparatory step, the position of the tire 2 with respect to the ridgeline 60 of the protrusion 44 is adjusted so that the plane including the rotation axis AL of the tire 2 and the ridgeline 60 of the protrusion 44 is orthogonal to the equatorial plane CL. It Then, as shown in FIG. 5, when the support shaft 54 is brought closer to the floor surface 56, the tire 2 is attached to the protrusion 44 so that the tip portion 58 of the protrusion 44 contacts the shoulder portion Sh of the tire 2. Set. When the setting of the tire 2 is completed, the measuring process is started. In FIG. 5, reference numeral PT is the inner end of the ridgeline 60 at the tip 58 of the protrusion 44. Reference symbol PS is an end of the outer layer 36 b of the belt 18.

  In the measuring process, the support shaft 54 is moved toward the floor surface 56. As a result, the support shaft 54 and the floor surface 56 approach each other. Then, the tire 2 comes into contact with the protrusion 44. As the support shaft 54 and the floor surface 56 come closer to each other, the protrusion 44 is pressed against the tire 2. The load detector outputs a detection signal regarding the load acting on the tire 2. The displacement gauge outputs a detection signal regarding the displacement of the support shaft 54. In this measuring step, the support shaft 54 and the floor surface 56 are brought close to each other, and the protrusion 44 is pressed against the tire 2. Thereby, in this measuring step, the load acting on the tire 2 and the displacement of the support shaft 54 are measured.

  In this test method, the distance between the support shaft 54 and the floor surface 56 is shortened, and the shoulder portion Sh of the tire 2 comes into contact with the tip end portion 58 of the protrusion 44, whereby a load acts on the shoulder portion Sh and the shoulder portion Sh Sh deforms. The shoulder portion Sh is pushed up by the protrusion 44 and then slides down from the tip portion 58 of the protrusion 44. Since the tip portion 58 of the protrusion 44 is sharp, the shoulder portion Sh slides down from the tip portion 58, so that a side cut occurs in the tire 2.

  In this test method, the contact position between the tire 2 and the protrusion 44 moves from the shoulder portion Sh to the side portion S by sliding the tire 2 from the tip portion 58 of the protrusion 44. The movement of the tire 2 with respect to the protrusion 44 in this test method is close to the movement of the tire 2 with respect to the rock, for example, when the tire 2 traveling on an uneven ground slides off the rock, although the rotation of the tire 2 is not accompanied. The side-cut state generated in the tire 2 by this test method is close to the side-cut state confirmed in actual running. This test method can repeatedly reproduce a sidecut in a state close to the sidecut state confirmed in actual running.

  FIG. 6 shows a measurement example of the load acting on the tire 2 with respect to the displacement of the support shaft 54. In FIG. 6, the horizontal axis is the displacement and the vertical axis is the load.

  In this test method, for example, the displacement-load curve shown in FIG. 6 is obtained. In FIG. 6, the decrease in the load indicated by the reference sign PD is based on the slippage from the protrusion 44 of the tire 2. The symbol PE is the end of the displacement-load curve. At this terminal PE, the internal pressure of the tire 2 is reduced due to the occurrence of the side cut, and the measurement is completed. From this displacement-load curve, for example, the load when a side cut occurs can be grasped. That is, this test method can determine the superiority or inferiority of the cut resistance by obtaining displacement-load curves for various tires 2 and comparing the loads when side cuts occur, for example.

  This test method can repeatedly reproduce the side cut in a state close to the state of the side cut confirmed in actual running, and can appropriately evaluate the cut resistance of the tire 2.

  As shown in FIG. 5, in this test method, in the step of setting the tire 2 on the protrusion 44, the tip portion 58 of the protrusion 44, specifically, the inner end PT of the ridge line 60 at the tip portion 58 is The tire 2 is set to the protrusion 44 so as to be located axially outside of the end PS of the outer layer 36b forming the belt 18.

  In this test method, the tire 2 is effectively slid off from the protrusion 44. The movement of the tire 2 with respect to the protrusion 44 in this test method is close to the movement of the tire 2 with respect to the rock when the tire 2 traveling on an uneven ground slides off the rock, for example. The side-cut state generated in the tire 2 by this test method is close to the side-cut state confirmed in actual running. From this viewpoint, in this test method, in the step of setting the tire 2 on the protrusion 44, the tip portion 58 of the protrusion 44, specifically, the inner end PT of the ridgeline 60 at the tip portion 58 constitutes the belt 18. The tire 2 is preferably set with respect to the protrusion 44 so as to be located axially outside of the end PS of the outer layer 36b.

  In FIG. 5, a double-headed arrow WH is an axial distance from the equatorial plane to the outer end PW of the tire 2. This distance WH is half the sectional width of the tire 2. A double-headed arrow W20 indicates an axial distance from the outer end PW of the tire 2 to the solid line L20. In this test method, the solid line L20 represents a position in the axial direction at which the distance W20 from the outer end PW of the tire 2 corresponds to 20% of the half WH of the sectional width of the tire 2.

  In this test method, the tire 2 is more preferably set to the protrusion 44 so that the tip 58 of the protrusion 44 is located axially outside the end PS of the outer layer 36b forming the belt 18. In the axial direction, a distance W20 from the outer end PW of the tire 2 is in a zone from a position L20 corresponding to 20% of a half WH of a sectional width of the tire 2 to an outer end PW of the tire 2. The tire 2 is set to the protrusion 44 so that the tip portion 58 of the protrusion 44 is located. As a result, in this test method, the tire 2 is more effectively slid off from the protrusion 44. The movement of the tire 2 relative to the protrusions 44 in this test method is quite close to the movement of the tire 2 relative to the rock, for example when the tire 2 traveling on an uneven terrain slides off the rock. The state of the side cut generated in the tire 2 by this test method is quite close to the side cut state confirmed in actual running.

  As described above, in this test method, the angle θ formed by the one slope 62 and the other slope 62 shown in FIG. 4 is an acute angle. The angle θ is preferably 80 ° or less from the viewpoint that the tire 2 is effectively slid off from the protrusions 44, and a sidecut in a state close to the sidecut state observed in actual running can be effectively generated. . This angle θ is preferably 30 ° or more from the viewpoint of being able to generate a side cut that allows comparison between the tires 2.

  In FIG. 2, a double-headed arrow HE is the height from the floor surface 56 to the inner end PT of the ridgeline 60 at the tip 58 of the protrusion 44. In the present invention, this height HE is the height of the protrusion 44 from the floor surface 56. In this test method, from the viewpoint that the tire 2 can be effectively slid off from the protrusions 44 and a side cut in a state close to the side cut state observed in actual running can be effectively generated, this height HE Is preferably higher than the sectional height of the tire 2 set in the test apparatus 42 (see JATMA, etc.). Specifically, this height HE is more preferably 1.3 times or more and more preferably 1.7 times or less of the sectional height.

  In this test method, the tire 2 is lowered by moving the support shaft 54 toward the floor surface 56 in the measuring step. In this test method, from the viewpoint that the tire 2 is effectively slid off from the protrusions 44 and a side cut in a state close to the state of the side cut observed in actual traveling can be effectively generated, this support shaft 54 The moving speed with respect to the floor surface 56 is preferably 50 mm / min or more, and preferably 150 mm / min or less.

  FIG. 7 shows a protrusion 64 as a modified example of the protrusion 44 provided on the test apparatus 42. 7A is a plan view of the protrusion 64, and FIG. 7B is a cross-sectional view of the protrusion 64 taken along line 7b-7b of FIG. 7A. In FIG. 7A, the left-right direction is the width direction of the test apparatus 42, and the up-down direction is the front-back direction of the test apparatus 42. In FIG. 7B, the left-right direction is the width direction of the test apparatus 42, and the up-down direction is the height direction of the test apparatus 42. The right side of the drawing corresponds to the widthwise inner side of the test apparatus 42.

  The tip portion 66 of the protrusion 64 is tapered upward in the height direction, like the protrusion 44 shown in FIGS. 3 and 4. The tip 66 is sharp. The tip portion 66 also has a ridge line 68 and a pair of slopes 70 extending to both sides of the ridge line 68, similarly to the tip portion 58 of the protrusion 44 described above. Although not shown, the distance between the one slope 70 and the other slope 70 gradually increases downward from the ridgeline 68. In the protrusion 64, the angle formed by the one slope 70 and the other slope 70 is an acute angle.

  As shown in FIG. 7A, the ridge line 68 extends in the width direction of the test apparatus 42 in the plan view of the protrusion 64. As described above, the width direction of the test device 42 corresponds to the axial direction of the tire 2 set in the test device 42. The ridgeline 68 of the protrusion 64 extends in the axial direction of the tire 2 set in the test apparatus 42 in a plan view of the protrusion 64. As shown in FIG. 7B, the ridgeline 68 of the protrusion 64 is inclined such that the outer end 68a thereof is located above the inner end PT in the height direction.

  In the protrusion 64, the side surface 72 located inside in the width direction of the test apparatus 42 includes the inner end PT of the ridgeline 68 as an apex. The side surface 72 of the protrusion 64 is inclined so that its apex PT is located outside the bottom side 72a of the side surface 72 in the width direction.

  In this test method, even if the protrusion 44 of the test apparatus 42 shown in FIG. 2 is replaced with the protrusion 64 shown in FIG. 7, the distance between the support shaft 54 and the floor surface 56 is shortened, and the shoulder of the tire 2 is reduced. By contacting the tip portion 66 of the protrusion 64 with the portion Sh, a load acts on the shoulder portion Sh and the shoulder portion Sh is deformed. The shoulder portion Sh is pushed up by the protrusion 64 and then slides down from the tip end portion 66 of the protrusion 64. Since the tip portion 66 of the protrusion 64 is sharp, the shoulder portion Sh slides down from the tip portion 66, so that a side cut occurs in the tire 2.

  In this test method, the shoulder portion Sh is slid off from the tip portion 66, so that the contact position between the tire 2 and the protrusion 64 moves from the shoulder portion Sh to the side portion S. The movement of the tire 2 with respect to the protrusion 64 in this test method is close to the movement of the tire 2 with respect to the rock, for example, when the tire 2 traveling on an uneven terrain slides off the rock, although the rotation of the tire 2 is not accompanied. The side-cut state generated in the tire 2 by this test method is close to the side-cut state confirmed in actual running.

  This test method can repeatedly reproduce the side cut in a state close to the state of the side cut confirmed in actual running, and can appropriately evaluate the cut resistance of the tire 2.

  FIG. 8 shows a protrusion 74 as another modification of the protrusion 44 provided on the test apparatus 42. 8A is a plan view of the protrusion 74, and FIG. 8B is a cross-sectional view of the protrusion 74 taken along the line 8b-8b of FIG. 8A. In FIG. 8A, the left-right direction is the width direction of the test apparatus 42, and the up-down direction is the front-back direction of the test apparatus 42. In FIG. 8B, the horizontal direction is the width direction of the test apparatus 42, and the vertical direction is the height direction of the test apparatus 42. The right side of the drawing corresponds to the widthwise inner side of the test apparatus 42.

  The tip portion 76 of the protrusion 74 is tapered upward in the height direction, like the protrusion 44 shown in FIGS. 3 and 4. This tip portion 76 is sharp. The tip portion 76 also has a ridge line 78 and a pair of slopes 80 extending on both sides of the ridge line 78, similarly to the tip portion 58 of the protrusion 44 described above. Although not shown, the distance between the one slope 80 and the other slope 80 gradually increases downward from the ridge line 78. In the projection 74, the angle formed by the one slope 80 and the other slope 80 is an acute angle.

  As shown in FIG. 8A, the ridgeline 78 extends in the width direction of the test apparatus 42 in the plan view of the protrusion 74. As described above, the width direction of the test device 42 corresponds to the axial direction of the tire 2 set in the test device 42. The ridgeline 78 of the protrusion 74 extends in the axial direction of the tire 2 set in the test apparatus 42 in a plan view of the protrusion 74. As shown in FIG. 8B, the ridgeline 78 of the projection 74 is inclined such that the outer end 78a thereof is located above the inner end PT in the height direction.

  In the protrusion 74, the side surface 82 located on the inner side in the width direction of the test apparatus 42 includes the inner end PT of the ridgeline 78 as an apex. The side surface 82 of the projection 74 is inclined so that its apex PT is located inside the bottom side 82a of the side surface 82 in the width direction.

  In this test method, even if the protrusion 44 of the test device 42 shown in FIG. 2 is replaced with the protrusion 74 shown in FIG. 8, the distance between the support shaft 54 and the floor surface 56 is shortened, and the shoulder of the tire 2 is reduced. When the portion Sh comes into contact with the tip end portion 76 of the protrusion 74, a load acts on the shoulder portion Sh and the shoulder portion Sh is deformed. The shoulder portion Sh is pushed up by the protrusion 74 and then slides down from the tip end portion 76 of the protrusion 74. Since the tip portion 76 of the protrusion 74 is sharp, the shoulder portion Sh slides off the tip portion 76, so that a side cut occurs in the tire 2.

  In this test method, the shoulder portion Sh is slid off from the tip portion 76, so that the contact position between the tire 2 and the protrusion 74 moves from the shoulder portion Sh to the side portion S. The movement of the tire 2 with respect to the protrusion 74 in this test method is close to the movement of the tire 2 with respect to the rock when the tire 2 traveling on an uneven terrain slides off the rock, although the rotation of the tire 2 is not accompanied. The side-cut state generated in the tire 2 by this test method is close to the side-cut state confirmed in actual running.

  This test method can repeatedly reproduce the side cut in a state close to the state of the side cut confirmed in actual running, and can appropriately evaluate the cut resistance of the tire 2.

  As is clear from the above description, according to the present invention, it is possible to repeatedly reproduce the side cut in a state close to the state of the side cut confirmed in actual running, and appropriately evaluate the cut resistance of the tire 2. It is possible to obtain a test method for the tire 2.

  The embodiments disclosed this time are illustrative in all points and not restrictive. The technical scope of the present invention is not limited to the above-described embodiment, and the technical scope includes all modifications within the scope equivalent to the configurations described in the claims.

  The tire testing method described above can be applied to the evaluation of the cut resistance of various types of tires.

2 ... Tire 4 ... Tread 6 ... Sidewall 14 ... Carcass 18 ... Belt 22 ... Tread surface 34 ... Carcass ply 36, 36a, 36b ... Layer 42 ... Test device 44, 64, 74 ... Protrusion 54 ... Support shaft 56 ... Floor surface 58, 66, 76 ... Tip portion 60, 68, 78 ... Ridge line 62, 70, 80 ...・ Slopes 72, 82 ... Sides

Claims (6)

By using a test device configured to press the protrusion against the tire by moving a support shaft that supports the tire toward the floor surface on which the protrusion is installed, cut resistance of the side portion of the tire A test method for evaluating sex,
A step of setting the tire with respect to the protrusion so that the tip end portion of the protrusion comes into contact with the shoulder portion of the tire,
A step of bringing the support shaft and the floor surface close to each other, and pressing the protrusion against the tire;
The tire testing method, wherein the protrusion has a sharp tip. The tire, in the radial direction inner side of the tread, comprises a belt laminated with a carcass, the belt is composed of a plurality of layers laminated in the radial direction,
In the step of setting the tire to the protrusion,
The tire is set with respect to the protrusion so that the tip end portion of the protrusion is located axially outside of the end of the outermost layer in the radial direction among the plurality of layers forming the belt. The method for testing a tire according to claim 1, wherein   In the axial direction, the distance from the outer end of the tire is located in the zone from the position corresponding to 20% of half the sectional width of the tire to the outer end of the tire, and the tip portion of the protrusion is located in the zone. The method for testing a tire according to claim 2, wherein the tire is set to the protrusion so as to do. The tip end portion of the protrusion has a ridge line extending in the axial direction of the tire set in the test device in a plan view of the protrusion, and a pair of slopes extending to both sides of the ridge line,
The tire testing method according to claim 1, wherein an angle formed by the pair of slopes is an acute angle in a cross section of the protrusion along a plane parallel to an equatorial plane of the tire.   The tire testing method according to claim 1, wherein a height of the protrusion from the floor surface is higher than a sectional height of a tire set in the testing device. The tire testing method according to claim 1, wherein a moving speed of the support shaft with respect to the floor surface is 50 mm / min or more and 150 mm / min or less.

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