JP2021041728A - Tire testing device and testing method - Google Patents

Abstract

To provide a tire testing device capable of precisely evaluating the durability of a tire.SOLUTION: A testing device 42 includes: a cooler 62 that cools down air to obtain cooling air; and at least one duct 64 that guides the cooling air. An end of the duct 64 is a blower opening 66 that blows the cooling air, and the blower opening 66 is placed in such a way that the cooling air is directed to a bead of a tire 2. A position of the blower opening 66 is within a range between equal to or greater than 60 degrees and equal to or smaller than 300 degrees around the axial center of the tire 2 when the ground center between the tire 2 and an outer circumference 52 is defined as zero degree.SELECTED DRAWING: Figure 2

Description

The present invention relates to a tire test device and a test method.

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

For example, in order to improve the durability of a tire, specifications such as a tire configuration are examined. The validity of this study is confirmed, for example, by assessing the durability of the tire. When the evaluation is performed by attaching tires to the vehicle, 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).

Japanese Unexamined Patent Publication No. 2009-133631

In the accelerated test, harsh test conditions are adopted. Therefore, in the accelerated test, damage other than damage due to fatigue due to repeated deformation may occur. For example, when the bead portion generates heat and the temperature of the bead portion reaches a temperature higher than expected, damage due to thermal deterioration (for example, damage due to cutting of the carcass cord) may occur instead of damage due to fatigue. I am concerned. This damage associated with cutting the carcass cord 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 Patent Document 1 described above, wind is applied to the bead portion on the contact patch side between the tire and the drum, which is considered to be a heat source.

The present inventors examined the case where the bead portion on the contact patch side between the tire and the drum was blown, and noticed the following points.
(1) Since a load acts on the contact patch side of the tire, the side portion on the contact patch side bends.
(2) Since the tread portion approaches the bead portion on the ground contact surface side, when the bead portion is blown with the air volume required for cooling, the tread portion is also exposed to the wind.
(3) Since the wind also hits the drum, the contact patch between the tire and the drum is also cooled.
(4) When wind is applied to the bead portion on the contact patch side between the tire and the drum, the tread portion is also cooled, and damage that may occur in the tread portion of the tire mounted on the vehicle (for example). The generation of belt edge loose (BEL) is suppressed.

In the test method described in Patent Document 1, although the temperature rise more than expected can be suppressed, there is a possibility that the damage that may occur in the tire mounted on the vehicle cannot be reproduced.

The present invention has been made in view of such an actual situation, and an object of the present invention is to provide a tire test device and a test method capable of accurately evaluating the durability of a tire.

The tire test device according to one aspect of the present invention is a device for running a tire on the outer peripheral surface of a drum and evaluating the durability of the tire. This test apparatus includes a cooler that cools air to make it cold air, and at least one duct that allows the cold air to pass through. 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 axis of the tire when the contact center between the tire and the outer peripheral surface is 0 °.

Preferably, in this tire test device, the angle formed by the direction of the cold air blown from the outlet with respect to the axial direction is 10 ° or more and 30 ° or less.

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

Preferably, in this tire test 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 test apparatus, the wind speed of the cold air is 10 m / s, and the temperature of the cold air is 20 ° C. or lower.

The tire test method according to one 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 the drum. This test method includes a step of running the tire on the outer peripheral surface while applying cold air to the bead portion of the tire. The position of the outlet for blowing the cold air is in the range of 60 ° or more and 300 ° or less with respect to the axis of the tire when the contact center between the tire and the outer peripheral surface is 0 °.

According to the tire test apparatus and test method of the present invention, it is possible to reproduce a damaged state 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 the tire test method according to the embodiment of the present invention. FIG. 2 is a plan view showing an outline of the test apparatus. FIG. 3 is a side view illustrating the cooling zone. FIG. 4 is a side view illustrating the arrangement of the outlets. FIG. 5 is a cross-sectional view illustrating the direction of the outlet.

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

In the present invention, the state in which the tire is incorporated in the 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 part of the tire are measured in a normal state.

Regular rims are rims defined in the standards on which the tire relies. The "standard rim" in the JATTA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are regular rims.

Regular internal pressure means the internal pressure defined in the standard on which the tire relies. The "maximum air pressure" in the JATMA standard, the "maximum value" in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are regular internal pressures. The normal 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. The "maximum load capacity" in the JATTA standard, the "maximum value" in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads. The normal load of a passenger car tire is, for example, a load corresponding to 88% of the load.

[tire]
FIG. 1 shows a part of a cross section of a pneumatic tire 2 (hereinafter, also referred to as a tire 2) used in the test method according to the embodiment of the present invention. The tire 2 is for a passenger car. In FIG. 1, the tire 2 is incorporated in the rim R (regular rim). FIG. 1 shows a tire 2 in a normal state.

FIG. 1 shows a part of a cross section of the tire 2 along a plane including the axis of the tire 2. In FIG. 1, the left-right 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 about its axis. The circumferential direction of the tire 2 is also the rotation direction of the tire 2. In FIG. 1, the alternate long and short dash line CL represents the equatorial plane of the tire 2.

In FIG. 1, the solid line BBL extending in the axial direction is the bead baseline. This bead baseline is a line that defines the rim diameter of the rim R (see JATTA and the like).

The tire 2 includes 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 inner liner 16.

The tread 4 includes a tread surface 18 that comes into contact with the road surface. A groove 20 is carved on the tread surface 18. In FIG. 1, the symbol PE is the intersection of the tread plane 18 and the equatorial plane. This intersection PE is the equator of this tire 2. The double-headed arrow HS is the radial distance from the bead baseline to the equatorial PE. This radial distance HS is the cross-sectional height of the tire 2.

Each sidewall 6 runs along the edge of the tread 4 and extends towards the clinch 8. Each clinch 8 is located radially inside the sidewall 6. The sidewall 6 and the clinch 8 form a side surface 24 which is connected to the end of the tread surface 18 and forms a part of the outer surface 22 of the tire 2.

Each bead 10 is located axially inside the clinch 8. The carcass 12 bridges between one bead 10 and the other bead 10. The belt 14 is laminated with the carcass 12 on the radial inside of the tread 4. The inner liner 16 is located inside the carcass 12. The inner liner 16 constitutes 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 including a 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 cords in parallel and a topping rubber covering these cords.

In the tire 2, the tread portion T is located on the outer side in the radial direction and is in contact with the road surface. The portion extending inward in the radial direction from the end of the tread portion T is the side portion W. The bead portion B is located inside the side portion W in the radial direction and is fitted to the rim R. The tire 2 has a tread portion T, a pair of side portions W, and a pair of bead portions B as portions.

In the tire 2, the tread 4, the belt 14, the carcass 12, and the inner liner 16 are included in the tread portion T. The side portion W includes a sidewall 6, a carcass 12, and an inner liner 16. The bead portion B includes a clinch 8, a bead 10, a carcass 12, and an inner liner 16.

As shown in FIG. 1, in a state where the tire 2 is fitted to the rim R, the inner peripheral surface 32 of the bead portion B comes into contact with the seat H of the rim R, and a part of the outer surface 34 of the bead portion B is abutted. It abuts on the flange F of the rim R.

Although the 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 a small truck, a tire for a truck or a bus, or a tire for a two-wheeled vehicle. 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 outline of the test apparatus 42. The test device 42 includes a drum 44, a drive unit 46, a grounding unit 48, and a cooling unit 50.

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

The drive unit 46 rotates and drives the drum 44. 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 includes a motor in which an output shaft is connected to a central shaft 54 to rotationally drive the drum 44. By controlling the rotation speed of the motor, the speed of the outer peripheral surface 52 of the drum 44, in other words, the speed of the tire 2 traveling on the outer peripheral surface 52 can be freely adjusted.

The grounding unit 48 supports the tire 2. The grounding 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. The ground contact 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. The tire shaft 58 is supported in parallel with the central shaft 54 of the drum 44. A tire 2 incorporated in the rim R is rotatably attached to the other end of the tire shaft 58. In this test device 42, the tire 2 is set so that the axis of the tire 2 is located in a virtual plane including the axis of the drum 44. In this test device 42, the rim R in which the tire 2 is incorporated may be a test rim corresponding to a regular rim.

The support portion 60 supports the tire shaft 58. Although not shown, the support 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 device 42, as the drum 44, the drive unit 46, and the grounding unit 48, the drum, the drive unit, and the grounding unit used in the conventional drum running test are preferably used. This test device 42 is a device for running the tire 2 on the outer peripheral surface 52 of the drum 44 and evaluating the durability of the tire 2.

The cooling unit 50 includes a cooler 62 and a duct 64. The cooler 62 cools the air and makes it cold air. In this test apparatus 42, a commercially available spot type cooler can be used as the cooler 62. The duct 64 is a pipeline. The duct 64 allows the cold air generated by the cooler 62 to pass through. One end of the duct 64 is connected to the 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 test device 42, the outlet 66 is arranged so that the bead portion B of the tire 2 is exposed to cold air. The cold air generated by the cooler 62 is sent to the bead portion B via the duct 64.

The cooling unit 50 is provided with at least one duct 64. In this test apparatus 42, the cooling unit 50 includes two ducts 64. As shown in FIG. 2, each duct 64 is branched in the middle, and two outlets 66 are provided. The cooling unit 50 includes four outlets 66. In this test device 42, the cooling unit 50 may be provided with four ducts 64, so that four outlets 66 may be provided. 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.

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

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

In FIG. 3, reference numeral PA is a shaft core of the tire 2 set on the tire shaft 58. The shaft core PA of the tire 2 corresponds to the shaft core of the tire shaft 58. Reference numeral PB is the axis of the central axis 54 of the drum 44. The solid line L0 is a straight line connecting the shaft core PA and the shaft core PB. In this test apparatus 42, the solid line L0 is also referred to as a reference line. Reference numeral P0 is an intersection of the reference line L0 and the outer peripheral surface 52 of the drum 44. In the test device 42, the intersection P0 is the center of contact between the tire 2 and the outer peripheral surface 52 of the drum 44.

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

In FIG. 3, the zone from the solid line La to the solid line Lb is represented by the double-headed arrow CZ. In this test device 42, the zone CZ is the cooling zone of the 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, this 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 °. To. As shown in FIG. 3, the cooling zone CZ does not include the contact surface between the tire 2 and the rim R.

In this test device 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 ° or more with respect to 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 °. It is in the range below °.

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

In FIG. 4, the solid lines L1 and L2 are straight lines extending in the radial direction from the axis PA. The solid line L1 passes through the center PM1, and the solid line L2 passes through the center PM2. In this test device 42, the solid line L1 specifies the circumferential position of the first outlet 66a, and the solid line L2 specifies the circumferential position of the second outlet 66b.

In FIG. 4, the angle θ1 is an 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 an 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 angle θ1 and the angle θ2 are represented by angles measured in the direction of the arrow from the reference line L0, similarly to the above-mentioned angles θa and θb.

In FIG. 4, the angle θ1 is 60 °. That is, the first outlet 66a is arranged at a position of 60 ° about the axis PA of the tire 2 when the ground contact center P0 is 0 °. The angle θ2 is 180 °. That is, the second outlet 66b is arranged at a position of 180 ° about the axis PA of the tire 2 when the ground contact center P0 is 0 °. Although not shown, the first outlet 66a and the second outlet 66b are arranged on the N-side side surface 24N as well as the S-side side surface 24S.

The positions of the first outlet 66a and the second outlet 66b shown in FIG. 4 are such that the axis PA of the tire 2 is set to 0 ° when the contact center P0 between the tire 2 and the outer peripheral surface 52 of the drum 44 is 0 °. At the center, it is in the range of 60 ° or more and 300 ° or less. 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 step, an adjustment step, and a running step. Each step will be described below.

In the preparatory step, the tire 2 is set in the test device 42. Specifically, the tire 2 to be evaluated is incorporated into the rim R. The inside of the tire 2 is filled with air, and the internal pressure of the tire 2 is adjusted. After the adjustment, the tire 2 is attached to the tire shaft 58 of the test device 42. The tire shaft 58 is moved toward the drum 44, and the tire 2 is pressed against the outer peripheral surface 52 of the drum 44. The amount of movement of the tire shaft 58 is controlled to adjust the load acting on the tire 2.

In the adjustment step, the position of the outlet 66 that blows out cold air is adjusted. As described above, in this test method, the outlet 66 is arranged in the cooling zone CZ.

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

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

In this test device 42, the outlet 66 is arranged so that the bead portion B of the tire 2 is exposed to cold air. In this test apparatus 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 with respect to 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 of. In this test device 42, since 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, the outlet 66 and the tread 4 arranged toward the bead portion B are arranged. A sufficient distance from is secured. In this test device 42, only the bead portion B is effectively cooled because the cold air blown from the outlet 66 is prevented from hitting the tread 4. In this test device 42, damage to the bead portion B due to thermal deterioration, which is unlikely to occur with the tire 2 mounted on the vehicle, is suppressed. This test device 42 can confirm whether or not the bead portion B is damaged due to fatigue due to repeated deformation and the tread portion T is damaged, which may occur in the tire 2 mounted on the vehicle. The test device 42 and the test method using the test device 42 reproduce a damaged state that may occur in the tire 2 mounted on the vehicle. The test device 42 and the test method can accurately evaluate the durability of the tire 2.

In this test apparatus 42, the bead portion B is cooled by cold air. From the viewpoint of effectively cooling the bead portion B, the temperature of the cold air is preferably 20 ° C. or lower. From the viewpoint that durability can be evaluated in an appropriate time, the temperature of this cold air is preferably 10 ° C. or higher.

In this test device 42, the wind speed of cold air is preferably 10 m / s or more from the viewpoint of effectively cooling the bead portion B. From the viewpoint that durability can be evaluated 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, the rim R, and the duct 64 along a plane including the center PM of the outlet 66 and the axis PA (not shown) of the tire 2. In FIG. 5, the left-right 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, the symbol PC represents the center position of the portion exposed to the cold air blown from the outlet 66. The central position PC is represented by a position indicating the lowest temperature, for example, by measuring the surface temperature of the bead portion B by thermography to identify a portion exposed to cold air. In FIG. 5, the solid line LF represents the direction in which the cold air blown from the outlet 66 flows. The direction in which the cold 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 an angle formed by the solid line LF with respect to the axial direction. In the test device 42, this angle θs is an angle formed by the direction of the cold air blown 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 outlet 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. The test device 42 and the test method using the test device 42 reproduce a damaged state that may occur in the tire 2 mounted on the vehicle. The test device 42 and the test method can accurately evaluate the durability of the tire 2.

In FIG. 5, the double-headed arrow D is the distance from the outlet 66 to the bead portion B. In this test apparatus 42, this distance D is represented by the shortest distance.

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

In FIG. 5, the double-headed arrow M is the inner diameter of the outlet 66. 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 by using this area as the area of the circle is specified as the inner diameter of the outlet 66. To.

In the test device 42 and the test method, the inner diameter M of the outlet 66 is preferably 20% or more, 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 reference numeral PW is the axial outer end of the tire 2. The outer end PW is specified based on a virtual side surface obtained on the assumption that the side surface 24 has no decoration such as a pattern or characters. 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 cross-sectional width. The outer end PW is a position where the tire 2 shows the maximum width (hereinafter, the maximum width position).

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

As shown in FIG. 5, in this test device 42, in the radial direction, the duct 64 is located inside the maximum width position PW so that the center position PC of the portion exposed to the cold air blown from the outlet 66 is located inside. It is arranged with respect to the tire 2. As a result, only the bead portion B is effectively cooled. The test device 42 and the test method using the test device 42 reproduce a damaged state that may occur in the tire 2 mounted on the vehicle. The test device 42 and the test method can accurately evaluate the durability of the tire 2. From this point of view, the duct 64 is arranged with respect to the tire 2 so that the central position PC of the portion exposed to the cold air blown from the outlet 66 is located inside the maximum width position PW in the radial direction. preferable.

In FIG. 5, the double-headed arrow HC is the radial distance from the bead baseline to the central position PC of the portion exposed to the cold air blown from the outlet 66.

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

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

The embodiments disclosed this time are exemplary in all respects and are 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 a range equivalent to the configuration described in the claims.

Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the present invention is not limited to such Examples.

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

In this embodiment, the first outlet and the second outlet are arranged in the cooling zone CZ shown in FIG. The mileage was set to 10,000 km. The size of the tire used for the evaluation was 235 / 65R16. The driving conditions are as follows. The assumed temperature of the bead portion in this evaluation is 80 ° C.
Drum diameter: 1707 mm
Speed: 80km / h
Internal pressure: 475 kPa
Load: 15.88kN
Atmospheric temperature: 28 ° C

[Comparative Example 1]
The tires are provided in the same manner as in the first embodiment 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 are as shown in Table 1 below. Durability was evaluated. 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 patch side between the tire and the drum. The test method of Comparative Example 1 is a conventional test method.

[Comparative Example 2]
The durability of the tire was evaluated in the same manner as in Example 1 except that the cooling unit was not 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 part of the flange of the rim was measured as the temperature of the bead part, and the temperature of the tread surface near the equator was measured as the temperature of the tread part. The results are shown in Table 1 below.

As shown in Table 1, in Comparative Example 2 in which the cooling unit was not provided, the temperature of the bead portion exceeded 80 ° C. In Comparative Example 2, since the temperature of the bead portion exceeds the assumed temperature, there is a risk of unintended damage.
In Comparative Example 1 in which the cold air outlet was arranged on the contact patch 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 is lowered by about 3 ° C. as compared with Comparative Example 2, the durability of the tread portion cannot be correctly evaluated in Comparative Example 1.
On the other hand, in the examples, the temperature of the bead portion was lower than that of Comparative Example 2 by 10 ° C., and the temperature of the bead portion was 80 ° C. or lower. In this example, it is estimated that no CBU damage will occur even if the running test is continued. Further, in this example, the temperature of the tread portion was about the same as that of Comparative Example 2, and the temperature of the tread portion did not decrease as in Comparative Example 1. Therefore, in this example, it is presumed that BEL-like damage will occur if the running test is continued.
As described above, in the embodiment, the occurrence of damage to the bead portion due to thermal deterioration, which is unlikely to occur in the tire mounted on the vehicle, is suppressed, while the repeated deformation that may occur in the tire mounted on the vehicle is caused. It is expected that it will be possible to confirm whether the bead part is damaged due to fatigue and the tread part is damaged. From this evaluation result, the superiority of the present invention is clear.

The technique described above for effectively cooling only the bead portion can be applied to various tire test methods.

2 ... Tire 4 ... Tread 6 ... Sidewall 8 ... Clinch 10 ... Bead 18 ... Tread surface 24 ... Side surface 42 ... Test equipment 44 ... Drum 52・ ・ ・ Outer surface of drum 44 62 ・ ・ ・ Cooler 64 ・ ・ ・ Ducts 66, 66a, 66b ・ ・ ・ Outlet T ・ ・ ・ Tread part B ・ ・ ・ Bead part

Claims (6)

A device for evaluating the durability of a tire by running the tire on the outer peripheral surface of the drum.
A cooler that cools the air and uses it as cold air,
With at least one duct for passing the cold air,
The tip of the duct is an outlet for blowing out the cold air.
The outlet is arranged so that the cold air hits the bead portion of the tire.
A tire test device in which the position of the outlet is in the range of 60 ° or more and 300 ° or less with respect to the axis of the tire when the contact center between the tire and the outer peripheral surface is 0 °. The tire test apparatus according to claim 1, wherein the angle formed by the direction of the cold air blown from the outlet with respect to the axial direction is 10 ° or more and 30 ° or less. The tire test apparatus according to claim 1 or 2, wherein the distance from the outlet to the bead portion is 30 mm or more and 100 mm or less. The tire test apparatus 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 test apparatus according to any one of claims 1 to 4, wherein the cold air has a wind speed of 10 m / s and the temperature of the cold air is 20 ° C. or lower. A method for evaluating the durability of a tire by running the tire on the outer peripheral surface of the drum.
Including a step of running the tire on the outer peripheral surface while applying cold air to the bead portion of the tire.
A tire test method in which the position of the outlet for blowing cold air is in the range of 60 ° or more and 300 ° or less with respect to the axis of the tire when the contact center between the tire and the outer peripheral surface is 0 °. ..

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