JP7302395B2 - Tire test equipment and test method - Google Patents

Description

The present invention relates to a tire testing apparatus and method.

A large load acts on the bead portion (hereinafter referred to as bead portion) of the tire that is fitted to the rim. In a running tire, for example, deformation and restoration are repeated at the bead portion. There is concern that the bead portion may suffer from fatigue-induced damage due to repeated deformation (hereinafter also referred to as fatigue-induced damage).

For example, in order to improve the durability of tires, specifications such as the configuration of tires are studied. The validity of this study is confirmed, for example, by evaluating the durability of the tire. If the tire is mounted on the vehicle and evaluated, this evaluation takes time. Therefore, an accelerated test is performed using a testing machine such as a drum testing machine (for example, Patent Document 1 below).

JP 2009-133631 A

Accelerated testing employs harsh test conditions. For this reason, accelerated testing may cause damage other than damage due to fatigue due to repeated deformation. For example, if the bead heats up and the temperature of the bead reaches a temperature higher than expected, damage due to thermal deterioration (for example, damage accompanying cutting of the carcass cord) may occur instead of damage due to fatigue. Concerned. This damage involving cutting of the carcass cords is also referred to as casing breakup (CBU).

It is necessary to cool the tires in order to suppress the temperature rise more than expected. In the test method described in the aforementioned Patent Document 1, wind is applied to the bead portion on the contact surface side between the tire and the drum, which is considered to be the heat source.

The present inventors studied the case where the bead portion on the side of the contact surface between the tire and the drum is exposed to wind, and found the following points.
(1) Since a load acts on the ground contact surface side of the tire, the side portion on the contact surface side bends.
(2) Since the tread portion approaches the bead portion on the side of the ground contact surface, when the bead portion is blown with an air volume necessary for cooling, the tread portion is also exposed to the air.
(3) Since the wind also hits the drum, the contact surface between the tire and the drum is also cooled.
(4) When the wind hits the bead on the side of the contact surface between the tire and the drum, the tread is also cooled, which may cause damage to the tread of the tire mounted on the vehicle (for example, The occurrence of belt edge loose (BEL) is suppressed.

Although the test method described in Patent Literature 1 suppresses an unexpected temperature rise, it may not be possible to reproduce damage that may occur in a tire mounted on a vehicle.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a tire testing apparatus and method capable of accurately evaluating tire durability.

A tire testing apparatus according to an aspect of the present invention is an apparatus for evaluating the durability of a tire by running the tire on the outer peripheral surface of a drum. The test apparatus comprises a cooler for cooling air into cold air and at least one duct for passing said cold air. The tip of the duct is an outlet for blowing out the cold air, and the outlet is arranged so that the cold air hits the bead portion of the tire. The position of the outlet is in the range of 60° or more and 300° or less with respect to the axial center of the tire when the ground contact center between the tire and the outer peripheral surface is 0°.

Preferably, in this tire testing apparatus, the direction of the cold air blown from the outlet makes an angle of 10° or more and 30° or less with respect to the axial direction.

Preferably, in this tire testing apparatus, the distance from the outlet to the bead portion is 30 mm or more and 100 mm or less.

Preferably, in this tire testing device, the inner diameter of the outlet is 20% or more and 60% or less of the cross-sectional height of the tire.

Preferably, in this tire testing apparatus, the cool air has a wind speed of 10 m/s and a temperature of 20° C. or less.

A tire testing method according to an aspect of the present invention is a method for evaluating the durability of the tire by running the tire on the outer peripheral surface of a drum. This test method includes the step of running the tire on the outer peripheral surface while blowing cool air to the bead portion of the tire. The position of the outlet for blowing out the cold air is in the range of 60° or more and 300° or less with respect to the axial center of the tire when the ground contact center between the tire and the outer peripheral surface is 0°.

INDUSTRIAL APPLICABILITY According to the tire testing apparatus and testing method of the present invention, it is possible to reproduce damage conditions that may occur in a tire mounted on a vehicle, so that the durability of the tire can be accurately evaluated.

FIG. 1 is a cross-sectional view showing an example of a pneumatic tire used in a tire testing method according to one embodiment of the present invention. FIG. 2 is a plan view showing an outline of the test equipment. FIG. 3 is a side view illustrating the cooling zone. FIG. 4 is a side view for explaining the arrangement of the outlets. FIG. 5 is a cross-sectional view for explaining the orientation of the outlet.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

In the present invention, a state in which the tire is mounted on a normal rim, the internal pressure of the tire is adjusted to the normal internal pressure, and no load is applied to the tire is referred to as a normal state. In the present invention, unless otherwise specified, the dimensions and angles of each portion of the tire are measured under normal conditions.

Regular rim means a rim defined in the standard on which the tire relies. A "standard rim" in the JATMA standard, a "design rim" in the TRA standard, and a "measuring rim" in the ETRTO standard are regular rims.

The normal internal pressure means the internal pressure defined in the standard on which the tire relies. The "maximum air pressure" in JATMA standards, the "maximum value" in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA standards, and the "INFLATION PRESSURE" in ETRTO standards are regular internal pressures. The regular internal pressure of a passenger car tire is, for example, 180 kPa.

Normal load means the load specified in the standard on which the tire relies. "Maximum load capacity" in the JATMA standard, "maximum value" in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and "LOAD CAPACITY" in the ETRTO standard are normal loads. A normal load for a passenger car tire is, for example, a load corresponding to 88% of the above load.

[tire]
FIG. 1 shows a part of a cross section of a pneumatic tire 2 (hereinafter also referred to as tire 2) used in a test method according to one embodiment of the present invention. This tire 2 is for passenger cars. In FIG. 1, the tire 2 is mounted on a rim R (regular rim). This FIG. 1 shows a tire 2 in normal condition.

FIG. 1 shows part of a cross-section of this tire 2 along a plane containing the axis of the tire 2 . In FIG. 1 , the horizontal direction is the axial direction of the tire 2 and the vertical direction is the radial direction of the tire 2 . The direction perpendicular to the paper surface of FIG. 1 is the circumferential direction of the tire 2 . The tire 2 rotates around its axis. The circumferential direction of the tire 2 is also the rotational direction of the tire 2 . In this FIG. 1 , the dashed-dotted line CL represents the equatorial plane of the tire 2 .

In FIG. 1, the axially extending solid line BBL is the bead baseline. This bead baseline is a line that defines the rim diameter of the rim R (see JATMA, etc.).

The tire 2 comprises a tread 4, a pair of sidewalls 6, a pair of clinches 8, a pair of beads 10, a carcass 12, a belt 14 and an innerliner 16.

The tread 4 has a tread surface 18 that contacts the road surface. Grooves 20 are cut in the tread surface 18 . In FIG. 1, the symbol PE is the intersection of the tread plane 18 and the equatorial plane. This intersection point PE is the equator of this tire 2 . The double arrow HS is the radial distance from the bead baseline to the equator PE. This radial distance HS is the cross-sectional height of the tire 2 .

Each sidewall 6 joins the edge of the tread 4 and extends toward the clinch 8 . Each clinch 8 is located radially inward of the sidewall 6 . The sidewall 6 and the clinch 8 form a side surface 24 that joins the ends of the tread surface 18 and forms part of the outer surface 22 of the tire 2 .

Each bead 10 is located axially inside the clinch 8 . A carcass 12 spans between one bead 10 and the other bead 10 . The belt 14 is laminated with the carcass 12 on the radially inner side of the tread 4 . An inner liner 16 is positioned inside the carcass 12 . The inner liner 16 forms the inner surface 26 of the tire 2 .

The tread 4, sidewall 6, clinch 8 and inner liner 16 are made of crosslinked rubber. The bead 10 includes a core 28 containing metal wire and an apex 30 made of crosslinked rubber. Although not shown, the carcass 12 and the belt 14 consist of a large number of parallel cords and a topping rubber covering these cords.

In this tire 2, the tread portion T is positioned radially outward and contacts the road surface. A side portion W extends radially inward from the end of the tread portion T. As shown in FIG. A bead portion B is positioned radially inward of the side portion W and fitted to the rim R. As shown in FIG. The tire 2 has a tread portion T, a pair of side portions W, and a pair of bead portions B as parts.

In this tire 2, a tread portion T includes a tread 4, a belt 14, a carcass 12 and an inner liner 16. As shown in FIG. Side portion W includes sidewall 6 , carcass 12 and inner liner 16 . Bead portion B includes clinch 8 , bead 10 , carcass 12 and innerliner 16 .

As shown in FIG. 1, when the tire 2 is fitted to the rim R, the inner peripheral surface 32 of the bead portion B abuts against the seat H of the rim R, and a part of the outer surface 34 of the bead portion B It abuts on the flange F of the rim R.

Although a passenger car tire has been described as the tire 2 to be evaluated, there is no particular limitation on the tire 2 to be evaluated in this test method. The tire 2 to be evaluated may be a tire for small trucks, a tire for trucks and buses, or a tire for two-wheeled vehicles. In this test method, various tires such as commercially available tires and tires under development are used as evaluation targets.

[Test equipment]
FIG. 2 shows an overview of the test device 42. As shown in FIG. This testing apparatus 42 comprises a drum 44 , a drive unit 46 , a grounding unit 48 and a cooling unit 50 .

In this testing device 42 , the tire 2 runs on the outer peripheral surface 52 of the drum 44 . This outer peripheral surface 52 is also referred to as a running surface. Drum 44 has a central axis 54 . The rotation of the central shaft 54 causes the drum 44 to rotate.

A drive unit 46 drives the drum 44 to rotate. The drive unit 46 includes a drum holder 56 that rotatably supports the central shaft 54 of the drum 44 . Although not shown, the drive unit 46 has a motor whose output shaft is connected to the central shaft 54 and drives the drum 44 to rotate. By controlling the rotation speed of this motor, the speed of the outer peripheral surface 52 of the drum 44, in other words, the speed of the tire 2 running on this outer peripheral surface 52, is freely adjusted.

A grounding unit 48 supports the tire 2 . The ground contact unit 48 moves the tire 2 toward the outer peripheral surface 52 of the drum 44 and brings the tire 2 into contact with the outer peripheral surface 52 . This grounding unit 48 includes a tire shaft 58 and a support portion 60 .

One end of the tire shaft 58 is supported by the support portion 60 . A tire axle 58 is supported parallel to the central axis 54 of the drum 44 . The tire 2 assembled on the rim R is rotatably attached to the other end of the tire shaft 58 . In this testing device 42 , the tire 2 is set so that the axial center of the tire 2 is positioned within a virtual plane including the axial center of the drum 44 . In this test device 42, the rim R into which the tire 2 is installed may be a test rim corresponding to a regular rim.

The support portion 60 supports the tire shaft 58 . Although not shown, the support portion 60 has a moving mechanism capable of moving the tire shaft 58 in the radial direction of the drum 44 . By moving the tire shaft 58 toward the drum 44 , the support portion 60 can press the tire 2 set on the tire shaft 58 against the outer peripheral surface 52 of the drum 44 . By controlling the amount of movement of the tire shaft 58, the tire 2 can be brought into contact with the outer peripheral surface 52 of the drum 44 with a free load.

In this test apparatus 42, the drum, drive unit and ground unit used in the conventional drum running test are preferably used as the drum 44, drive unit 46 and ground unit 48. FIG. This testing device 42 is a device for evaluating the durability of the tire 2 by running the tire 2 on the outer peripheral surface 52 of the drum 44 .

Cooling unit 50 comprises cooler 62 and duct 64 . The cooler 62 cools the air into cool air. A commercially available spot-type cooler can be used as the cooler 62 in the test device 42 . Duct 64 is a pipeline. The duct 64 passes cold air generated by the cooler 62 . One end of duct 64 is connected to cooler 62 . The other end of the duct 64, in other words, the tip of the duct 64, is an outlet 66 for blowing cold air. In this testing device 42 , the blowout port 66 is arranged so that cool air is applied to the bead portion B of the tire 2 . Cool air generated by the cooler 62 is sent to the bead portion B through the duct 64 .

At least one duct 64 is provided in the cooling unit 50 . In this test apparatus 42 , the cooling unit 50 has two ducts 64 . As shown in FIG. 2, each duct 64 is branched in the middle and two outlets 66 are provided. This cooling unit 50 has four outlets 66 . In this test apparatus 42 , the cooling unit 50 may be provided with four ducts 64 to provide four outlets 66 . The number of ducts 64 and the number of outlets 66 in the cooling unit 50 are appropriately determined according to the specifications of the test device 42 .

Tire 2 has a pair of side surfaces 24 extending from the ends of tread surface 18 . As shown in FIG. 2, in this test apparatus 42, two of the four outlets 66 provided in the cooling unit 50 are connected to one side surface 24 (hereinafter referred to as the S-side side surface 24S). , and the remaining two outlets 66 are arranged to face the other side surface 24 (hereinafter referred to as the N-side side surface 24N).

FIG. 3 shows a side view of test device 42 . 3 shows the drum 44 of the testing device 42 and the tire 2 set on the testing device 42. As shown in FIG. The side surface 24 of the tire 2 shown in FIG. 3 is the S-side side surface 24S. Arrow A is the direction of rotation of drum 44 and arrow B is the direction of rotation of tire 2 .

In FIG. 3 , symbol PA is the axial center of the tire 2 set on the tire shaft 58 . The axial center PA of the tire 2 coincides with the axial center of the tire shaft 58 . Symbol PB is the axis of the central shaft 54 of the drum 44 . A solid line L0 is a straight line connecting the axis PA and the axis PB. In this test device 42, the solid line L0 is also called a reference line. A symbol P0 is an intersection point between the reference line L0 and the outer peripheral surface 52 of the drum 44 . In this testing device 42 , this intersection point P 0 is the contact center between the tire 2 and the outer peripheral surface 52 of the drum 44 .

In FIG. 3 , solid lines La and Lb are straight lines extending radially from the axis PA of the tire 2 . The angle θa is the angle formed by the solid line La with respect to the reference line L0. The angle θb is the angle formed by the solid line Lb with respect to the reference line L0. As shown in FIG. 3, the angles θa and θb are represented by angles measured from the reference line L0 in the directions of the arrows. The angles θa and θb may be expressed by angles measured from the reference line L0 in the direction opposite to the direction of the arrow.

In FIG. 3, the zone from solid line La to solid line Lb is represented by double arrow CZ. In this testing apparatus 42 , zone CZ is the cooling zone for tire 2 . In this test apparatus 42, the angle θa formed by the solid line La with respect to the reference line L0 is 60°, and the angle θb formed by the solid line Lb with respect to the reference line L0 is 300°. That is, the cooling zone CZ is specified as a range of 60° or more and 300° or less around the axis PA of the tire 2 when the contact center P0 between the tire 2 and the outer peripheral surface 52 of the drum 44 is 0°. be. As shown in FIG. 3, the contact surface between the tire 2 and the rim R is not included in the cooling zone CZ.

In this test apparatus 42, the outlet 66 of the duct 64 is arranged in the cooling zone CZ. That is, in this test device 42, the position of the outlet 66 is 60° or more and 300° from the center of the axis PA of the tire 2 when the contact center P0 between the tire 2 and the outer peripheral surface 52 of the drum 44 is 0°. ° is in the range below.

FIG. 4 shows an example of the arrangement of the outlets 66. As shown in FIG. FIG. 4 shows a state in which two outlets 66 are arranged on the S side surface 24S. In this test device 42, each outlet 66 has a circular shape. Reference PM1 is the center of one of the outlets 66, namely the first outlet 66a, and reference PM2 is the center of the other outlet 66, namely the second outlet 66b. In addition, when the shape of the outlet 66 is represented by a shape other than a circle, the center of gravity of the shape is represented as the center PM of the outlet 66 .

In FIG. 4, solid lines L1 and L2 are straight lines extending radially from the axis PA. A solid line L1 passes through the center PM1, and a solid line L2 passes through the center PM2. In this test apparatus 42, the solid line L1 identifies the circumferential position of the first outlet 66a, and the solid line L2 identifies the circumferential position of the second outlet 66b.

In FIG. 4, the angle θ1 is the angle formed by the solid line L1 with respect to the reference line L0. This angle θ1 represents the circumferential position of the first outlet 66a. The angle θ2 is the angle formed by the solid line L2 with respect to the reference line L0. This angle θ2 represents the circumferential position of the second outlet 66b. The angles .theta.1 and .theta.2 are represented by angles measured from the reference line L0 in the directions of the arrows, like the angles .theta.a and .theta.b.

In FIG. 4, the angle θ1 is 60°. That is, the first blowout port 66a is arranged at a position of 60° around the axis PA of the tire 2 when the ground contact center P0 is 0°. The angle θ2 is 180°. That is, the second blowout port 66b is arranged at a position of 180° around the axis PA of the tire 2 when the ground contact center P0 is 0°. Although not shown, the N-side side surface 24N is also provided with the first outlet 66a and the second outlet 66b similarly to the S-side side surface 24S.

The positions of the first outlet 66a and the second outlet 66b shown in FIG. It is in the range of 60° or more and 300° or less at the center. In this test device 42, the first outlet 66a and the second outlet 66b are arranged in the cooling zone CZ.

Using the test device 42 described above, the test method for the tire 2 is performed as follows. This test method is a method for evaluating the durability of the tire 2 by running the tire 2 on the outer peripheral surface 52 of the drum 44 . This test method includes a preparation process, an adjustment process and a running process. Each step will be described below.

In the preparation process, the tire 2 is set on the testing device 42 . Specifically, the tire 2 to be evaluated is assembled into the rim R. Air is filled inside the tire 2 and the internal pressure of the tire 2 is adjusted. After adjustment, the tire 2 is mounted on the tire axle 58 of the testing device 42 . The tire shaft 58 is moved toward the drum 44 to press the tire 2 against the outer peripheral surface 52 of the drum 44 . The load acting on the tire 2 is adjusted by controlling the amount of movement of the tire shaft 58 .

In the adjustment process, the position of the blowout port 66 for blowing out cool air is adjusted. As mentioned above, in this test method, the outlet 66 is placed in the cooling zone CZ.

In the running process, the drum 44 is rotated and the tire 2 is run on the outer peripheral surface 52 of the drum 44 at a predetermined speed. The cooler 62 is driven to blow cool air adjusted to a predetermined temperature onto the bead portion B of the tire 2 at a predetermined wind speed. In this running process, the tire 2 is run on the outer peripheral surface 52 of the drum 44 while blowing cool air to the bead portion B of the tire 2 . In this test method, the running process ends when the running distance reaches a preset distance or when the tire 2 is damaged.

In this test method, the presence or absence of damage, the degree of damage, etc. are confirmed by observing the appearance of the tire 2 after completion of the running process. In this test method, the durability of the tire 2 is evaluated as described above.

In this testing device 42 , the blowout port 66 is arranged so that cool air is applied to the bead portion B of the tire 2 . In this testing device 42, the bead portion B is sufficiently cooled.

In this test device 42, the position of the outlet 66 is 60° or more and 300° or less around the axis PA of the tire 2 when the contact center P0 between the tire 2 and the outer peripheral surface 52 of the drum 44 is 0°. in the range of In this test device 42, the outlet 66 is arranged not in the zone where the tire 2 is deformed but in the zone where the tire 2 is restored. Sufficient distance is ensured. Since the cool air blown out from the blowout port 66 is prevented from hitting the tread 4, only the bead portion B is effectively cooled in the test device 42. In this test device 42, the occurrence of damage to the bead portion B due to heat deterioration, which is difficult to occur in the tire 2 mounted on a vehicle, is suppressed. This testing device 42 can check whether damage to the bead portion B and damage to the tread portion T due to fatigue due to repeated deformation, which may occur in the tire 2 mounted on a vehicle. This test device 42 and the test method using this test device 42 reproduce damage conditions that may occur in a tire 2 mounted on a vehicle. This testing device 42 and testing method can accurately evaluate the durability of the tire 2 .

In this testing device 42, the bead portion B is cooled by cold air. From the viewpoint of effectively cooling the bead portion B, the temperature of the cool air is preferably 20° C. or less. The temperature of the cool air is preferably 10° C. or higher from the viewpoint of evaluating the durability in an appropriate time.

In this test device 42, the wind speed of the cool air is preferably 10 m/s or more from the viewpoint of effectively cooling the bead portion B. From the viewpoint of being able to evaluate the durability in an appropriate time, the wind speed of this cold air is preferably 20 m/s or less.

FIG. 5 shows a cross-section of the tire 2 and rim R and the duct 64 along a plane containing the center PM of the outlet 66 and the axis PA of the tire 2 (not shown). In FIG. 5 , the lateral direction is the axial direction of the tire 2 and the vertical direction is the radial direction of the tire 2 . The direction perpendicular to the paper surface of FIG. 5 is the circumferential direction of the tire 2 .

In FIG. 5, reference character PC represents the center position of the portion that is hit by the cool air blown out from the outlet 66 . This central position PC is indicated by the position showing the lowest temperature, for example, by measuring the surface temperature of the bead portion B by thermography to specify the portion exposed to the cold air. In FIG. 5, a solid line LF represents the direction in which the cold air blown from the blowing port 66 flows. The direction in which the cool air flows is specified by confirming the direction of the center position PC with respect to the center PM of the outlet 66 . The angle θs is the angle formed by the solid line LF with respect to the axial direction. In this test device 42, the angle θs is the angle formed by the direction of the cool air blown out from the outlet 66 with respect to the axial direction.

In this test apparatus 42, the angle θs formed by the direction of the cold air blown from the blowing port 66 with respect to the axial direction is preferably 10° or more, and preferably 30° or less. As a result, only the bead portion B is effectively cooled. This test device 42 and the test method using this test device 42 reproduce damage conditions that may occur in a tire 2 mounted on a vehicle. This testing device 42 and testing method can accurately evaluate the durability of the tire 2 .

In FIG. 5, the double arrow D indicates the distance from the blowout port 66 to the bead portion B. As shown in FIG. In this test device 42, this distance D is represented by the shortest distance.

In the test apparatus 42 and the test method, the distance D from the blowout port 66 to the bead portion B is preferably 30 mm or more, and preferably 100 mm or less, from the viewpoint of effectively cooling the bead portion B.

In FIG. 5, a double arrow M indicates the inner diameter of the outlet 66. As shown in FIG. In addition, when the shape of the outlet 66 is represented by a shape other than a circle, the area of the outlet 66 is measured, and the diameter calculated as the area of the circle is specified as the inner diameter of the outlet 66. be.

In the test apparatus 42 and the test method, the inner diameter M of the outlet 66 is preferably 20% or more and preferably 60% or less of the cross-sectional height HS of the tire 2 from the viewpoint of effectively cooling the bead portion B.

In FIG. 5 , the symbol PW is the axial outer end of the tire 2 . This outer edge PW is specified based on a virtual side surface obtained by assuming that the side surface 24 has no decoration such as a pattern or letters. The axial distance from one outer end PW to the other outer end PW is the maximum width of this tire 2, that is, the cross-sectional width. The outer end PW is the position where the tire 2 exhibits the maximum width (hereinafter referred to as the maximum width position).

In this test device 42, the duct 64 is preferably arranged with respect to the tire 2 so that the entire outlet 66 is located inside the maximum width position PW. In this testing device 42, only the bead portion B is effectively cooled. This test device 42 and the test method using this test device 42 reproduce damage conditions that may occur in a tire 2 mounted on a vehicle. This testing device 42 and testing method can accurately evaluate the durability of the tire 2 .

As shown in FIG. 5, in the test apparatus 42, the duct 64 is arranged so that the center position PC of the portion hit by the cold air blown from the blowing port 66 is positioned inside the maximum width position PW in the radial direction. It is arranged with respect to the tire 2 . As a result, only the bead portion B is effectively cooled. This test device 42 and the test method using this test device 42 reproduce damage conditions that may occur in a tire 2 mounted on a vehicle. This testing device 42 and testing method can accurately evaluate the durability of the tire 2 . From this point of view, it is preferable that the duct 64 be arranged with respect to the tire 2 so that the center position PC of the portion hit by the cold air blown from the blowing port 66 is located inside the maximum width position PW in the radial direction. preferable.

In FIG. 5, a double-headed arrow HC is the radial distance from the bead base line to the center position PC of the portion hit by the cold air blown from the blowing port 66 .

In the test apparatus 42 and the test method, the radial distance HC is preferably 20% or more and preferably 40% or less of the cross-sectional height HS of the tire 2 from the viewpoint that only the bead portion B is effectively cooled.

As described above, according to the testing device 42 for the tire 2 of the present invention and the testing method using this testing device 42, only the bead portion B is effectively cooled. This test device 42 and the test method using this test device 42 reproduce damage conditions that may occur in a tire 2 mounted on a vehicle. This testing device 42 and testing method can accurately evaluate the durability of the tire 2 .

The embodiments disclosed this time are illustrative in all respects and are not restrictive. The technical scope of the present invention is not limited to the above-described embodiments, but includes all modifications within the scope of equivalents to the configuration described in the claims.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited only to these Examples.

[Example]
Using the test apparatus shown in FIG. 2, a running test was conducted based on the specifications shown in Table 1 below to evaluate the durability of the tire.
In Table 1, the number (S side) corresponds to the number of outlets provided on the S side surface. The number (N side) corresponds to the number of outlets provided on the N side surface. θ1 corresponds to the angle θ1 representing the circumferential position of the first outlet. θ2 corresponds to the angle θ2 representing the circumferential position of the second outlet. M/HS corresponds to the ratio of the outlet inner diameter M to the tire section height HS. θs corresponds to the angle θs formed by the direction of the cool air blown from the outlet with respect to the axial direction. D corresponds to the distance from the outlet to the bead.

In this example, the cooling zone CZ shown in FIG. 3 was provided with a first outlet and a second outlet. The mileage was set at 10000 km. The tire size used for evaluation was 235/65R16. The running conditions are as follows. The assumed temperature of the bead portion in this evaluation is 80°C.
Drum diameter: 1707mm
Speed: 80km/h
Internal pressure: 475kPa
Load: 15.88kN
Ambient temperature: 28°C

[Comparative Example 1]
The tire was manufactured in the same manner as in Example 1, except that the angle θ1 representing the circumferential position of the first outlet and the angle θ2 representing the circumferential position of the second outlet were set as shown in Table 1 below. A durability evaluation was performed. In Comparative Example 1, the first outlet and the second outlet were arranged in a zone other than the cooling zone CZ shown in FIG. 3, that is, on the contact surface side between the tire and the drum. The test method of Comparative Example 1 is a conventional test method.

[Comparative Example 2]
Tire durability was evaluated in the same manner as in Example 1, except that no cooling unit was provided. The test method of Comparative Example 2 is a conventional test method.

[Temperature of each part of the tire]
During the running test, the temperature of each part of the tire was measured using a non-contact thermometer. The temperature of the outer portion of the flange of the rim was measured as the bead temperature, and the temperature of the tread surface near the equator was measured as the tread temperature. The results are shown in Table 1 below.

As shown in Table 1, in Comparative Example 2 in which no cooling unit was provided, the temperature of the bead exceeded 80°C. In Comparative Example 2, the temperature of the bead portion exceeds the assumed temperature, so there is a risk of unintended damage.
In Comparative Example 1, in which the cooling air outlet was arranged on the contact surface side between the tire and the drum, the temperature of the bead portion was 80°C. Therefore, in Comparative Example 1, the temperature of the bead portion does not exceed the assumed temperature. However, since the temperature of the tread portion was about 3° C. lower than in Comparative Example 2, in Comparative Example 1, the durability of the tread portion cannot be evaluated correctly.
On the other hand, in Example, the temperature of the bead portion was lower than that of Comparative Example 2 by 10° C., and the temperature of this bead portion was 80° C. or lower. In this example, it is presumed that CBU damage will not occur even if the running test is continued. Furthermore, in this example, the temperature of the tread portion was about the same as in Comparative Example 2, and no temperature drop as in Comparative Example 1 was observed in the temperature of this tread portion. Therefore, in this embodiment, if the running test is continued, it is presumed that damage such as BEL will occur.
In this way, in the embodiment, damage to the bead portion due to heat deterioration, which is unlikely to occur in a tire mounted on a vehicle, is suppressed. It is expected that we will be able to confirm the presence or absence of bead damage and tread damage due to fatigue. From this evaluation result, the superiority of the present invention is clear.

The technique of effectively cooling only the bead portion described above can also be applied to various tire testing methods.

2 Tire 4 Tread 6 Sidewall 8 Clinch 10 Bead 18 Tread surface 24 Side surface 42 Test device 44 Drum 52 . . Outer peripheral surface of drum 44 62. Cooler 64. Duct 66, 66a, 66b.

Claims (6)

A device for evaluating the durability of the tire by running the tire on the outer peripheral surface of the drum,
a cooler for cooling the air into cold air;
At least one duct for passing the cold air,
The tip of the duct is an outlet for blowing out the cold air,
The air outlet is arranged so that the cool air hits the bead portion of the tire,
A tire testing apparatus, wherein the position of the outlet is in the range of 60° or more and 300° or less around the axial center of the tire when the ground contact center between the tire and the outer peripheral surface is 0°. 2. The tire testing apparatus according to claim 1, wherein the direction of the cool air blown out from the outlet makes an angle of 10[deg.] or more and 30[deg.] or less with respect to the axial direction. The tire testing device according to claim 1 or 2, wherein the distance from the blowout port to the bead portion is 30 mm or more and 100 mm or less. The tire testing device according to any one of claims 1 to 3, wherein the inner diameter of the outlet is 20% or more and 60% or less of the cross-sectional height of the tire. The tire testing apparatus according to any one of claims 1 to 4, wherein the cold air has a wind speed of 10 m/s and a temperature of 20°C or less. A method for evaluating the durability of the tire by running the tire on the outer peripheral surface of the drum,
A step of running the tire on the outer peripheral surface while applying cold air to the bead portion of the tire,
A method for testing a tire, wherein the position of the outlet for blowing out cold air is in the range of 60° or more and 300° or less around the axial center of the tire when the center of contact between the tire and the outer peripheral surface is 0°. .

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