JP7339495B2 - Tire test method and tire test equipment - Google Patents

Description

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

In a pneumatic tire, cracks may occur at the groove bottom of the groove formed in the tread portion due to distortion during running of the vehicle, deterioration over time, or the like. Various methods have been conventionally proposed as test methods for evaluating the degree of occurrence of groove cracks.

For example, in the test methods described in Patent Documents 1 and 2, after leaving the tire to be tested in an ozone atmosphere for a predetermined period, the tire is pressed against the rotating drum and a load is applied to the tire while a running test is performed using the rotating drum. By doing so, groove cracks in the market are reproduced and evaluated. In addition, in the test method described in Patent Document 3, while performing a running test with a rotating drum while applying a load to the tire to be tested, by injecting ozone into the tire, Groove cracks are reproduced and evaluated.

JP-A-2006-84290 JP 2014-100977 A JP-A-2008-26228

However, in the conventional test method, the occurrence of groove cracks may differ greatly between the tested tire and the actual tire, resulting in insufficient reproducibility in the market.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a tire testing method and a tire testing apparatus capable of improving market reproducibility of groove cracks.

In order to solve the above-described problems and achieve the object, the tire testing method according to the present invention provides a test method for a pneumatic tire exposed to ozone in an atmosphere adjusted to a predetermined temperature. Further, the position of the pneumatic tire in the tire circumferential direction is the same, and the load is applied in the direction perpendicular to the tire width direction of the pneumatic tire.

Moreover, in the tire test method, the load applied to the pneumatic tire is preferably in the range of 40% or more and 100% or less of the maximum load capacity of the pneumatic tire.

Moreover, in the tire test method, the concentration of the ozone with which the pneumatic tire is exposed is preferably in the range of 50 pphm or more and 250 pphm or less.

Moreover, in the tire test method, the temperature of the atmosphere is preferably in the range of 30°C or higher and 70°C or lower.

In the tire test method, the pneumatic tire preferably has an internal pressure within a range of 60% or more and 100% or less of the maximum air pressure of the pneumatic tire.

Further, in the above tire test method, it is preferable that the internal pressure is decreased with the lapse of time during which the load is applied to the pneumatic tire.

Moreover, in the tire test method, it is preferable to change the temperature of the atmosphere while continuing to apply the load to the pneumatic tire.

Further, in order to solve the above-described problems and achieve the object, a tire testing apparatus according to the present invention includes an air conditioner capable of adjusting the temperature in the test chamber to a predetermined temperature, and an ozone supply to the test chamber. A load is applied in a direction perpendicular to the tire width direction of the pneumatic tire at the same position in the tire circumferential direction of the pneumatic tire in the test chamber as the ozone supply device that can be used. and a load mechanism device.

Further, in the above tire testing device, the load mechanism device is connected to a contact surface that contacts the tread contact surface of the pneumatic tire and a rim wheel mounted on the pneumatic tire, and is connected to the contact surface. A variable connecting member is provided, and the load is applied to the pneumatic tire by changing the distance between the connecting member and the contact surface.

INDUSTRIAL APPLICABILITY The tire testing method and tire testing apparatus according to the present invention have the effect of improving market reproducibility of groove cracks.

FIG. 1 is a configuration diagram showing a tire testing apparatus according to an embodiment. 2 is a view taken along line AA in FIG. 1. FIG. FIG. 3 is a flow diagram showing the procedure for testing by the tire testing method according to the embodiment. FIG. 4 is a modified example of the tire testing apparatus according to the embodiment, and is an explanatory diagram of a case where a load sensor 50 is provided. FIG. 5 is a chart showing the evaluation results of the tire test method.

EMBODIMENT OF THE INVENTION Below, embodiment of the tire testing method and tire testing apparatus which concerns on this invention is described in detail based on drawing. In addition, this invention is not limited by this embodiment. In addition, constituent elements in the following embodiments include those that can be replaced and easily conceived by those skilled in the art, or those that are substantially the same.

[Embodiment]
FIG. 1 is a configuration diagram showing a tire testing apparatus 1 according to an embodiment. 2 is a view taken along line AA in FIG. 1. FIG. 1 and 2 schematically show the overall configuration of a tire testing apparatus 1. FIG. In the following description, the up-down direction of the tire testing apparatus 1 under normal use conditions will be described as the up-down direction of the tire testing apparatus 1 as well, and the horizontal direction under normal use conditions of the tire testing apparatus 1 will be referred to as the tire testing apparatus 1. 1 is also described as the horizontal direction.

A tire testing apparatus 1 according to the present embodiment is applied to a testing apparatus that reproduces the occurrence of groove cracks by reproducing the use condition of a pneumatic tire 100 mounted on a vehicle. Specifically, the tire testing apparatus 1 according to the present embodiment reproduces the state of the pneumatic tire 100 mounted on a vehicle that has been parked for a long period of time without running. Applied to test equipment that reproduces the occurrence of groove cracks in

The tire testing apparatus 1 includes a test chamber 10 , an air conditioner 20 , an ozone supply device 30 and a load mechanism device 40 . The test room 10 is a room for forming a space isolated from the outside air when testing the pneumatic tire 100 . Note that the test chamber 10 does not have to be completely isolated from the outside air. It is sufficient if the atmosphere inside the test chamber 10 can be generally separated from the outside air.

The air conditioner 20 can adjust the temperature inside the test chamber 10 to a predetermined temperature. The air conditioner 20 is installed outside the test chamber 10 and can adjust the temperature inside the test chamber 10 through a vent 22 that communicates with the inside of the test chamber 10 . Specifically, the air conditioner 20 has an operation unit (not shown) for performing input operations such as temperature setting, and is capable of arbitrary temperature setting. A temperature sensor 25 capable of detecting the temperature of the ambient atmosphere is arranged inside the test chamber 10 , and the air conditioner 20 is electrically connected to the temperature sensor 25 . The air conditioner 20 can acquire the temperature detected by the temperature sensor 25, and compares the temperature set by the operation unit with the temperature in the test chamber 10 acquired by the temperature sensor 25. , the operation is performed so that the temperature in the test chamber 10 approaches the temperature set by the operation unit.

The ozone supply device 30 can generate ozone and supply the generated ozone into the test chamber 10 . The ozone supply device 30 is installed outside the test chamber 10 and is capable of supplying ozone into the test chamber 10 through a vent 32 communicating with the inside of the test chamber 10 . Specifically, the ozone supply device 30 has an operation unit (not shown) for performing input operations such as setting the concentration of ozone, and is capable of setting an arbitrary concentration of ozone. An ozone concentration sensor 35 capable of detecting the concentration of ozone in the surrounding atmosphere is arranged inside the test chamber 10 , and the ozone supply device 30 is electrically connected to the ozone concentration sensor 35 . . The ozone supply device 30 can acquire the concentration of ozone detected by the ozone concentration sensor 35, and the concentration of ozone set by the operation unit and the concentration of the ozone in the test chamber 10 acquired by the ozone concentration sensor 35. By comparing the ozone concentration with the ozone concentration, the operating operation is performed so that the ozone concentration in the test chamber 10 approaches the ozone concentration set by the operation unit.

Note that the air conditioner 20 and the ozone supply device 30 may be installed inside the test chamber 10 . If the air conditioner 20 can adjust the temperature in the test chamber 10 and the ozone supply device 30 can supply ozone into the test chamber 10, the installation position of the device itself can be changed even inside the test chamber 10. Either outside or outside.

The load mechanism device 40 is installed inside the test chamber 10 and can apply a load to the pneumatic tire 100 in the test chamber 10 in a direction orthogonal to the tire width direction of the pneumatic tire 100. It has become. In the following description, the tire radial direction refers to a direction orthogonal to a tire rotation axis (not shown) that is the rotation axis of the pneumatic tire 100 . Moreover, the tire circumferential direction refers to the circumferential direction with the tire rotation axis as the central axis. Moreover, the tire width direction refers to a direction parallel to the tire rotation axis.

In this embodiment, the load mechanism device 40 uses a flat spot generator 41 that can easily apply a load to the pneumatic tire 100 . The flat spot generator 41 has a ground surface plate 42 , supports 44 and connecting members 47 . The contact surface plate 42 has a contact surface 43 that contacts the tread contact surface 101 of the pneumatic tire 100 to be tested. The ground surface plate 42 is formed in, for example, a rectangular plate-like shape, and the contact surface 43 is a flat surface formed by one surface of the ground surface plate 42 in the thickness direction. The ground surface plate 42 is arranged with the contact surface 43 directed upward. The post 44 is a rod-shaped columnar member erected on the ground surface plate 42 . In this embodiment, the strut 44 is formed of a solid structure with a circular cross-section and a length greater than the outer diameter of the pneumatic tire 100 to be tested. A screw thread (not shown) is formed on one end of the post 44, and a fixing member 45 is fixed in the vicinity of the screw thread to be gripped with a tool when attaching the post 44 to the ground surface plate 42. there is A screw hole (not shown) penetrating through the ground surface plate 42 in the thickness direction of the ground surface plate 42 is formed at the position where the post 44 is attached to the ground surface plate 42 .

The post 44 extends to the contact surface 43 side of the ground surface plate 42 by screwing a screw thread formed on one end side into a screw hole formed in the ground surface plate 42 from the contact surface 43 side. It is attached so that the existing direction is almost perpendicular to the contact surface 43 . As a result, the pillars 44 are erected on the ground surface plate 42 . Also, two struts 44 are erected on the ground surface plate 42, and the two struts 44 are arranged at intervals wider than the width of the pneumatic tire 100 to be tested in the tire width direction.

The connecting member 47 is a member that supports the pneumatic tire 100 on the ground surface plate 42 . The connecting member 47 can support the pneumatic tire 100 by being connected to both the rim wheel 110 attached to the pneumatic tire 100 and the strut 44 erected on the ground surface plate 42 . ing.

Specifically, the connecting member 47 is a cylindrical member, and has a connecting portion 48 connected to the rim wheel 110 at a position near the center in the longitudinal direction. The connecting portion 48 is formed in a flange-like shape and provided in the connecting member 47, and is located at a position corresponding to an attachment hole (not shown) through which a bolt is passed when the rim wheel 110 is attached to the vehicle in the rim wheel 110. is formed with an insertion hole (not shown). As a result, the connecting portion 48 is formed by aligning the mounting hole formed in the rim wheel 110 and the insertion hole formed in the connecting portion 48, and connecting the bolt 49 to both holes so that the bolt 49 and the nut ( (not shown) can be connected to the rim wheel 110 by screwing together.

Further, the connecting member 47 is formed with a through-hole passing through the connecting member 47 in the radial direction of the connecting member 47 formed in a cylindrical shape, and the support column 44 can be passed through the through-hole. there is The connecting member 47 allows both of the two pillars 44 erected on the ground surface plate 42 to pass through the through holes. , are formed at intervals of two supports 44 erected on the ground surface plate 42 . Thereby, the connecting member 47 can move relative to the support column 44 in the extending direction of the support column 44 . That is, the connecting member 47 is vertically movable along the post 44 and can change the distance from the contact surface 43 . The flat spot generator 41 moves the connecting member 47 vertically along the strut 44, thereby applying a load in the direction along the strut 44, that is, in the vertical direction, to the pneumatic tire 100. It's becoming

On the other hand, the strut 44 has a screw thread formed in a predetermined range including at least a region whose distance from the contact surface 43 is approximately the same as the radius of the pneumatic tire 100 . For this reason, the connecting member 47 has a restraining member 46 such as a nut that is screwed into the screw thread at a position above the connecting member 47 in the thread formed in the post 44 in a state where the post 44 is passed through the through hole. By screwing together, the upward movement of the connecting member 47 can be restricted. By using, for example, a wing nut as the restraining member 46, the restraining member 46 can be easily rotated without using a tool, and the position for restricting the movement of the connecting member 47 can be determined.

The tire testing apparatus 1 according to the present embodiment is configured as described above, and the operation thereof will be described below. FIG. 3 is a flow diagram showing the procedure for testing by the tire testing method according to the embodiment. When testing the pneumatic tire 100 with the tire testing apparatus 1, the pneumatic tire 100 is mounted on the rim wheel 110 and adjusted to a predetermined internal pressure (step ST1). In this case, the internal pressure of the pneumatic tire 100 is within the range of 60% or more and 100% or less of the maximum air pressure of the pneumatic tire 100 . The internal pressure of the pneumatic tire 100 is preferably in the range of 80% or more and 100% or less of the maximum air pressure of the pneumatic tire 100 . The maximum air pressure referred to here is the "maximum air pressure" defined by JATMA, the maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" defined by TRA, or the "INFLATION PRESSURES" defined by ETRTO.

Next, the pneumatic tire 100 is mounted on the flat spot generator 41 (step ST2). When the pneumatic tire 100 is mounted on the flat spot generator 41, the connecting member 47 is connected to the rim wheel 110 mounted on the pneumatic tire 100, and the strut 44 is passed through the through hole formed in the connecting member 47. . As a result, the pneumatic tire 100 is oriented with respect to the ground surface plate 42 so that the rotational axis of the pneumatic tire 100 is parallel to the contact surface 43 of the ground surface plate 42 . In this state, by moving the connecting member 47 along the strut 44 , the portion of the tread contact surface 101 of the pneumatic tire 100 facing the contact surface 43 is brought into contact with the contact surface 43 . That is, the pneumatic tire 100 is placed on the ground surface plate 42 with the tread contact surface 101 of the pneumatic tire 100 in contact with the contact surface 43 , and the pneumatic tire 100 is supported by the struts 44 and the connecting members 47 . do. Thus, the pneumatic tire 100 is attached to the flat spot generator 41 .

Next, a load is applied to the pneumatic tire 100 (step ST3). A load is applied to the pneumatic tire 100 by changing the distance between the connecting member 47 and the contact surface 43 . That is, by moving the connecting member 47 connected to the rim wheel 110 in the vertical direction along the strut 44 to change the distance between the connecting member 47 and the contact surface 43, the rim mounted on the pneumatic tire 100 is changed. The wheel 110 is moved vertically.

On the other hand, since the tread contact surface 101 of the pneumatic tire 100 is in contact with the contact surface 43, the relative positional relationship of the pneumatic tire 100 with respect to the contact surface 43 does not change. For this reason, the portion of the pneumatic tire 100 that is mainly located below the rim wheel 110 receives a load from the rim wheel 110 that is crushed vertically by the rim wheel 110 and the contact surface 43 . be. When a load is applied to the pneumatic tire 100, the restraining member 46 is rotated along the threads formed on the struts 44, thereby pressing the restraining member 46 from above the connecting member 47 and moving the connecting member 47 downward. move to As a result, a downward load in the vertical direction can be applied from the connecting member 47 to the rim wheel 110, and the load is applied to the pneumatic tire 100 from the rim wheel 110 to which the downward load is applied. . That is, the flat spot generator 41 applies a load to the pneumatic tire 100 in a direction orthogonal to the tire width direction of the pneumatic tire 100 at the same position in the tire circumferential direction.

A restraining member 46 that moves the connecting member 47 downward by rotating along the thread of the post 44 is screwed with the thread of the post 44 , so that it can maintain its position in the vertical direction with respect to the post 44 . can. Therefore, the restraining member 46 can maintain the vertical position of the connecting member 47 at the position where the load is applied to the pneumatic tire 100, and the load is applied to the pneumatic tire 100. state can be maintained. That is, the flat spot generator 41 to which the pneumatic tire 100 is mounted continuously applies a load to the pneumatic tire 100 at the same position in the tire circumferential direction. At this time, the magnitude of the load applied to the pneumatic tire 100 is, for example, the magnitude that causes the pneumatic tire 100 mounted on the vehicle to deform to the same extent as the deformation caused by the weight of the vehicle. load.

Next, the temperature and ozone concentration of the atmosphere in the test chamber 10 are adjusted (step ST4). Of these, the temperature is adjusted by the air conditioner 20 and the ozone concentration is adjusted by the ozone supply device 30 . That is, by inputting a predetermined temperature to the operation unit of the air conditioner 20 and operating the air conditioner 20, the temperature of the atmosphere in the test chamber 10 is adjusted to a predetermined temperature. In this embodiment, the temperature of the atmosphere in the test chamber 10 is set within the range of 30° C. or higher and 70° C. or lower. Similarly, by inputting a predetermined ozone concentration to the operation unit of the ozone supply device 30 and operating the ozone supply device 30 to supply ozone into the test chamber 10, the ozone in the atmosphere in the test chamber 10 is The concentration is adjusted to a predetermined concentration and the pneumatic tire 100 is exposed to ozone. In this embodiment, the concentration of ozone with which the pneumatic tire 100 is exposed is in the range of 50 pphm or more and 250 pphm or less.

The temperature of the atmosphere around the pneumatic tire 100 in the test chamber 10 is preferably in the range of 40° C. or higher and 60° C. or lower, and the concentration of ozone that exposes the pneumatic tire 100 in the test chamber 10 is , 120 pphm to 180 pphm. In this manner, the temperature is adjusted by the air conditioner 20, and ozone is supplied from the ozone supply device 30 to adjust the ozone concentration, thereby exposing the pneumatic tire 100 to ozone in an atmosphere adjusted to a predetermined temperature. A load is applied to the pneumatic tire 100 in this state.

Next, it is determined whether or not a specified time has passed (step ST5). The specified time in this case is to prevent groove cracks occurring in the groove bottom of the groove portion 102 formed in the tread portion of the pneumatic tire 100 when the pneumatic tire 100 is actually used. It is set in advance as a time that can be reproduced by continuing to apply a load in a state where the Specifically, the specified time is set in advance as a time during which groove cracks occurring in the groove bottom of the groove portion 102 of the pneumatic tire 100 can be reproduced when the vehicle is stopped for a long period of time. The specified time is preferably set within a range of 8 hours or more and 40 hours or less. The pneumatic tire 100 is attached to the flat spot generator 41, a load is applied, and the ozone concentration in the test chamber 10 is adjusted to expose the pneumatic tire 100 to ozone. has passed the specified time.

It should be noted that whether or not the specified time has elapsed can be determined by the operator continuing to measure the elapsed time after a load is applied to the pneumatic tire 100 and the pneumatic tire 100 is exposed to ozone. may be determined by the operator. Alternatively, the air conditioner 20 or the ozone supply device 30 may be provided with a notification means (not shown) for notifying the operator of information by voice or display, and a timer, and the elapsed time after the operation of these devices is started. A timer may be used to measure the elapsed time, and the notification means may notify the operator whether or not the elapsed time has passed the specified time. Further, when a timer is provided in the air conditioner 20 or the ozone supply device 30, the operation of these devices may be stopped when the elapsed time has passed a specified time.

When it is determined that the measured elapsed time has not passed the specified time (step ST5, No determination), the pneumatic tire 100 is exposed to ozone in an atmosphere adjusted to a predetermined temperature. Load is continued to be applied to the pneumatic tire 100 in this state.

On the other hand, when it is determined that the elapsed time has passed the specified time (step ST5, Yes determination), the pneumatic tire 100 is removed from the flat spot generator 41, and the occurrence of groove cracks is observed (step ST6). , to end the test. That is, in an atmosphere adjusted to a predetermined temperature, the elapsed time in a state where the pneumatic tire 100 is exposed to ozone and a load is applied to the pneumatic tire 100 elapses a preset predetermined elapsed time. Then, visually observe the occurrence of groove cracks.

In the tire test method according to the above embodiment, a load is applied to the same position in the tire circumferential direction of the pneumatic tire 100 in an atmosphere adjusted to a predetermined temperature. can be tested by reproducing the mode of use of Specifically, by continuously applying a load to the same position in the tire circumferential direction of the pneumatic tire 100, the impact on the pneumatic tire 100 when the vehicle equipped with the pneumatic tire 100 is stopped for a long period of time. can be reproduced by testing.

In other words, the pneumatic tire 100 may be damaged not only when the vehicle is running, but also when the vehicle is stopped. In particular, when the vehicle is parked for a long period of time, the pneumatic tire 100 is continuously subjected to a load in the same direction in the same location for a long period of time, which may cause damage such as groove cracks. . When testing the damage, durability, etc. of the pneumatic tire 100, if the test is performed using a rotating drum, changes in the pneumatic tire 100 during running of the vehicle can be reproduced. Regarding the change of the pneumatic tire 100 when the vehicle is stopped for a long period of time, it is very difficult to test using a rotating drum. On the other hand, in the present embodiment, since the load is applied to the same position in the tire circumferential direction of the pneumatic tire 100, it is possible to reproduce the change of the pneumatic tire 100 when the vehicle is stopped for a long period of time.

In addition, since the pneumatic tire 100 is exposed to ozone when the test is performed while applying a load to the pneumatic tire 100, deterioration of the pneumatic tire 100 can be accelerated. As a result, the change in the pneumatic tire 100 when the vehicle with the pneumatic tire 100 is parked for a long period of time can be reproduced in a short period of time, and the change occurs in the groove portion 102 when the pneumatic tire 100 is actually used. Groove cracks can be reproduced in a short time. As a result, market reproducibility of groove cracks can be improved.

In addition, since the concentration of ozone that exposes the pneumatic tire 100 is in the range of 50 pphm or more and 250 pphm or less, it is more efficient while ensuring reproducibility of changes in the pneumatic tire 100 when the vehicle is stopped for a long time. Evaluation can be performed in a short period of time by accelerating deterioration. In other words, when the ozone concentration is 50 pphm, the ozone concentration is too low, so there is a possibility that the pneumatic tire 100 is less likely to deteriorate even if it is exposed to ozone. In this case, there is a possibility that the efficiency of accelerated deterioration evaluation, which evaluates in a short period of time by accelerating deterioration, tends to deteriorate. In addition, when the ozone concentration exceeds 250 pphm, the ozone concentration is too high, so the correlation with the natural deterioration of the pneumatic tire 100 during normal use decreases, and the change in the pneumatic tire 100 during the test There is a risk that the in-fill tire 100 is likely to deviate from the changes that occur when the in-fill tire 100 is mounted on a vehicle and actually used.

On the other hand, when the concentration of ozone that exposes the pneumatic tire 100 is in the range of 50 pphm or more and 250 pphm or less, while ensuring the reproducibility of the change of the pneumatic tire 100 when the vehicle is stopped for a long time, Degradation promotion evaluation can be performed by efficiently promoting degradation. As a result, the market reproducibility of groove cracks can be more reliably improved.

In addition, since the temperature of the atmosphere in the test chamber 10 is in the range of 30 ° C. or more and 70 ° C. or less, it is more efficient while ensuring the reproducibility of the change of the pneumatic tire 100 when the vehicle is stopped for a long time. Evaluation can be performed in a short period of time by accelerating deterioration. In other words, when the temperature of the atmosphere in the test chamber 10 is less than 30° C., the temperature is too low, so the reactivity of the pneumatic tire 100 to ozone tends to decrease, and there is a possibility that the efficiency of deterioration acceleration evaluation tends to deteriorate. There is In addition, when the temperature of the atmosphere in the test chamber 10 exceeds 70°C, the temperature is too high, so the heat aging phenomenon of the pneumatic tire 100 becomes remarkable, and the change of the pneumatic tire 100 during the test is There is a possibility that the tire 100 is likely to deviate from the changes that occur when the tire 100 is mounted on a vehicle and actually used.

On the other hand, when the temperature of the atmosphere in the test chamber 10 is in the range of 30° C. or more and 70° C. or less, while ensuring the reproducibility of the change of the pneumatic tire 100 when the vehicle is stopped for a long time, Degradation promotion evaluation can be performed by efficiently promoting degradation. As a result, the market reproducibility of groove cracks can be more reliably improved.

In addition, when performing the test, the internal pressure of the pneumatic tire 100 is set within the range of 60% or more and 100% or less of the maximum air pressure, so the test is performed in a state closer to the actual use of the pneumatic tire 100. It can be performed. As a result, the market reproducibility of groove cracks can be more reliably improved.

Further, the tire testing apparatus 1 according to the above embodiment includes an air conditioner 20, an ozone supply device 30, and a load mechanism device 40. Since the load is applied to the same position in the , the test can be performed by reproducing the actual usage of the pneumatic tire 100 mounted on the vehicle. Specifically, by continuously applying a load to the same position in the tire circumferential direction of the pneumatic tire 100, the impact on the pneumatic tire 100 when the vehicle equipped with the pneumatic tire 100 is stopped for a long period of time. can be reproduced. As a result, the tire testing apparatus 1 can reproduce changes in the pneumatic tire 100 when the vehicle is parked for a long period of time.

Further, since the tire testing apparatus 1 supplies ozone into the test chamber 10 by the ozone supplying device 30, deterioration of the pneumatic tire 100 can be hastened. As a result, the change in the pneumatic tire 100 when the vehicle with the pneumatic tire 100 is parked for a long period of time can be reproduced in a short period of time, and the change occurs in the groove portion 102 when the pneumatic tire 100 is actually used. Groove cracks can be reproduced in a short time. As a result, market reproducibility of groove cracks can be improved.

In addition, the load mechanism device 40 changes the distance between the connecting member 47 connected to the rim wheel 110 and the contact surface 43 that contacts the tread contact surface 101 of the pneumatic tire 100, thereby increasing the load on the pneumatic tire 100. Therefore, an appropriate load can be applied to the pneumatic tire 100 . In other words, the pneumatic tire 100 is attached to the vehicle by attaching the rim wheel 110 to the vehicle. A load is applied from the wheel 110 to the pneumatic tire 100 . Therefore, when a load is applied to the pneumatic tire 100, the distance between the connecting member 47 and the contact surface 43 is changed, and the distance between the rim wheel 110 and the contact surface 43 is changed. , the load can be applied to the pneumatic tire 100 in the same manner as the load acts on the pneumatic tire 100 when the vehicle is stopped. Therefore, an appropriate load can be applied to the pneumatic tire 100, and groove cracks occurring in the groove portion 102 when the pneumatic tire 100 is actually used can be reproduced with higher accuracy. As a result, the market reproducibility of groove cracks can be more reliably improved.

In addition, since the load mechanism device 40 uses the flat spot generator 41 which has a support 44 erected on the ground surface plate 42 and moves the connecting member 47 vertically along the support 44, the structure is simple. A load mechanism device 40 can be implemented. As a result, the market reproducibility of groove cracks can be improved at low cost.

[Modification]
In addition, although the load applied to the pneumatic tire 100 is not specified in the above-described embodiment, the load applied to the pneumatic tire 100 may be specified. FIG. 4 is a modified example of the tire testing apparatus 1 according to the embodiment, and is an explanatory diagram of a case where a load sensor 50 is provided. In the flat spot generator 41, as shown in FIG. 4, a load sensor 50 capable of detecting a load is placed on the contact surface 43 of the ground surface plate 42, and the load applied to the pneumatic tire 100 can be detected. You may do so. It is preferable to use the load sensor 50 formed in a sheet shape. By using a sheet-shaped load sensor 50 and placing it on the contact surface 43 , the load sensor 50 itself forms the contact surface 43 that contacts the tread contact surface 101 of the pneumatic tire 100 . can do. A load sensor 50 arranged to detect the load of the pneumatic tire 100 is arranged between the two struts 44 so as to be able to contact the tread contact surface 101 of the pneumatic tire 100 . The load sensor 50 is also connected to a display (not shown) that displays information so that the detected load can be displayed on the display.

When the pneumatic tire 100 is mounted on the flat spot generator 41 having the load sensor 50, the portion of the tread contact surface 101 of the pneumatic tire 100 facing the contact surface 43 is replaced with the load sensor 50 on the contact surface 43. is placed in contact with the That is, the pneumatic tire 100 is placed on the ground surface plate 42 with the tread contact surface 101 of the pneumatic tire 100 in contact with the position where the load sensor 50 is arranged on the contact surface 43 . The pneumatic tire 100 is supported by the connecting member 47 .

When the pneumatic tire 100 is attached to the flat spot generator 41 having the load sensor 50 and a load is applied to the pneumatic tire 100, the load is measured by the load sensor 50 and applied. In other words, since the pneumatic tire 100 is in contact with the load sensor 50 , the load applied to the pneumatic tire 100 can be detected by the load sensor 50 . Therefore, the load applied to pneumatic tire 100 is adjusted based on the load detected by load sensor 50 . Specifically, since the load detected by the load sensor 50 is displayed on the display unit connected to the load sensor 50, the restraint member 46 is rotated while visually checking the load displayed on the display unit, and the connecting member 47 is moved up and down. Adjust position in direction. This keeps the load applied to the pneumatic tire 100 within a predetermined range. Since the restraining member 46 is screwed into the thread of the post 44 , once the load is adjusted by adjusting the vertical direction of the connecting member 47 , the rotation of the restraining member 46 is stopped at that position so that the connecting member 47 position in the vertical direction can be maintained, and the load can be maintained.

The load applied to the pneumatic tire 100 , which is adjusted in this way, is within the range of 40% or more and 100% or less of the maximum load capacity of the pneumatic tire 100 . The load applied to the pneumatic tire 100 is preferably within a range of 50% or more and 70% or less of the maximum load capacity of the pneumatic tire 100 . The maximum load capacity referred to here is the "maximum load capacity" defined by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" defined by TRA, or the "LOAD CAPACITY" defined by ETRTO.

The load applied to the pneumatic tire 100 can be measured, and when the test is performed, the load applied to the pneumatic tire 100 is within the range of 40% or more and 100% or less of the maximum load capacity of the pneumatic tire 100. As a result, the test can be conducted in a state closer to the actual usage of the pneumatic tire 100 . As a result, the market reproducibility of groove cracks can be more reliably improved.

In the above-described embodiment, after the pneumatic tire 100 is attached to the flat spot generator 41 and the test is started, the conditions such as the atmosphere around the pneumatic tire 100 are not changed. You can change the conditions. For example, the internal pressure of the pneumatic tire 100 may be reduced as time passes while the load is applied to the pneumatic tire 100 . The internal pressure of the pneumatic tire 100 may be lowered once or multiple times during the period from the start of the test until the specified time elapses. The internal pressure in this case is adjusted by the operator while measuring the internal pressure.

Since the internal pressure of the pneumatic tire 100 may gradually decrease even if the vehicle is stopped without running, the pressure of the pneumatic tire 100 increases as the load is applied after the start of the test. By lowering the internal pressure of the tire 100, changes in the pneumatic tire 100 when the vehicle is parked for a long time can be reproduced with higher accuracy. The degree of reduction in the internal pressure of the pneumatic tire 100 is preferably within the range of 20 kPa or more and 30 kPa or less in 24 hours. As a result, groove cracks that occur in the groove portion 102 when the pneumatic tire 100 is actually used can be reproduced with higher accuracy. As a result, the market reproducibility of groove cracks can be more reliably improved.

Further, when changing the conditions during the test, the temperature of the atmosphere around the pneumatic tire 100 in the test chamber 10 may be changed while the load is continuously applied to the pneumatic tire 100 . When the vehicle is parked for a long period of time, the temperature may change, for example due to the change of seasons. Therefore, by changing the temperature of the atmosphere around the pneumatic tire 100 when performing the test while applying a load, it is possible to reproduce the groove crack including the effect of temperature change on the groove crack. can. As a result, the market reproducibility of groove cracks can be more reliably improved.

In the above-described embodiment, the ozone supply device 30 supplies ozone into the test chamber 10 from a position away from the pneumatic tire 100. Ozone may be supplied in the vicinity of the portion in contact with 42 . For example, an ozone injection unit (not shown) that injects ozone supplied from the ozone supply device 30 is arranged near the contact surface 43 of the ground contact surface plate 42, and the tread contact surface 101 of the pneumatic tire 100 and the contact surface plate 42 are arranged. Ozone may be injected from the ozone injection part near the portion where the contact surface 43 of the contact surface 43 contacts. Groove cracks that occur when the vehicle is parked for a long period of time occur in a portion of the groove portion 102 that is located near the contact surface. At least, ozone should be supplied to the vicinity of the portion where the tread contact surface 101 and the contact surface 43 contact each other.

Further, when the ozone injection section injects ozone near the portion where the tread contact surface 101 and the contact surface 43 are in contact with each other, it is possible to effectively evaluate deterioration acceleration using ozone. In other words, since the ozone injection unit injects ozone intensively near the ground contact surface of the pneumatic tire 100, it is possible to inject the ozone airflow with a high flow velocity to the pneumatic tire 100, and the ozone is consumed and becomes reactive. Air with a low volatility can be removed by ozone with a high flow velocity. Therefore, it is possible to increase the probability of new active ozone molecules colliding with the pneumatic tire 100, and to improve the reactivity when the deterioration is accelerated by ozone. As a result, deterioration can be efficiently accelerated by ozone, and deterioration acceleration evaluation can be performed effectively. As a result, the market reproducibility of groove cracks can be more reliably improved.

Furthermore, when ozone is injected near the portion where the tread contact surface 101 and the contact surface 43 are in contact with each other by the ozone injection unit, side cracks, which are cracks generated in the sidewall portion of the pneumatic tire 100, can also be easily reproduced. can. That is, among the sidewall portions of the pneumatic tire 100, the sidewall portions located on the outer side in the width direction of the vehicle are exposed to sunlight, and thus are easily irradiated with ultraviolet rays and easily deteriorated by the ultraviolet rays. As a result, side cracks are more likely to occur as a result of this deterioration. are also more susceptible to ozone exposure. As a result, deterioration of the sidewall portion can also be accelerated by ozone, and side cracks that occur when the vehicle is parked for a long period of time can be reproduced in a short period of time. As a result, market reproducibility of side cracks can also be improved.

In the above-described embodiment, the connection member 47 of the flat spot generator 41 can be connected to the rim wheel 110 attached to the pneumatic tire 100 by using the bolt 49. , the connecting member 47 may be connected to the rim wheel 110 by other methods. The connecting member 47 may be connected to the rim wheel 110 by being formed integrally with the rim wheel 110, for example. The connection member 47 that can move relative to the support 44 in the direction in which the support 44 extends can be connected to the rim wheel 110 so as to be movable together with the rim wheel 110 .

Moreover, in the above-described embodiment, the flat spot generator 41 is used as the load mechanism device 40 , but the load mechanism device 40 may be other than the flat spot generator 41 . The load mechanism device 40 may have, for example, a power source driven by electric power, and may be configured to apply a load to the pneumatic tire 100 with power generated by the power source. In this case, it is preferable to control the load applied to the pneumatic tire 100 within a predetermined range by applying the load from the power source while detecting the load applied to the pneumatic tire 100 .

Moreover, the tire testing method according to the above-described embodiment may be performed together with other tests. For example, before or after the tire test method according to the above-described embodiment, an exposure test is performed in which the pneumatic tire 100 is exposed to the shade for a long time while the internal pressure of the pneumatic tire 100 is set to a predetermined internal pressure and a predetermined load is applied. may When a vehicle is parked outdoors for a long period of time, it may be parked in the shade for a long time. Therefore, by conducting an additional exposure test in the shade, the environment of the pneumatic tire 100 installed on a vehicle parked for a long period of time can be reproduced. can do. As a result, groove cracks can be reproduced with higher accuracy.

Alternatively, before or after the tire testing method according to the embodiment described above, a test in which the pneumatic tire 100 is left in a high-temperature atmosphere without supplying ozone may be performed. By additionally conducting a test in which the pneumatic tire 100 is left in a high-temperature atmosphere, it is possible to reproduce the effect of hardening of the rubber due to high temperature, and the groove generated in the pneumatic tire 100 used in a high-temperature environment can be reproduced. Cracks can be reproduced with higher accuracy. As a result, the market reproducibility of groove cracks can be improved more reliably.

[Example]
FIG. 5 is a chart showing the evaluation results of the tire test method. Evaluation tests performed on the tire testing method according to the present invention and a tire testing method of a comparative example for comparison with the tire testing method according to the present invention will be described below.

In the evaluation test, a pneumatic tire 100 having a tire nominal of 225/65R17 size specified by JATMA was mounted on a rim wheel 110 of JATMA standard, the air pressure was 90% of the maximum air pressure, and the load was 60% of the maximum load capacity. %, and the temperature in the test chamber 10 was adjusted to 50° C. in an ozone atmosphere with an ozone concentration of 150 pphm.

The evaluation method counts the number of groove cracks that finally occur after completion of the test in each tire test method, and expresses the number of groove cracks as an index with the number of groove cracks in the actual vehicle example described later being 100. It was evaluated by Specifically, for groove cracks, the length of groove cracks is measured at each groove portion 102, and all groove cracks with a length of 1 mm or more that can be visually confirmed are counted, and the number of groove cracks in an actual vehicle example described later is set to 100. It was evaluated by expressing it with an index. In this evaluation, the larger the index, the more groove cracks there are, and the closer the index is to 100, the closer the number of groove cracks to actual vehicle examples, and the better the reproducibility of groove cracks. ing.

Groove cracks are classified into three categories, large (25 mm or more), medium (5 mm or more and less than 25 mm), and small (less than 5 mm), according to the length of the groove crack, and the ratio of large, medium, and small is evaluated. You may Alternatively, regardless of the length of groove cracks, according to the number of groove cracks that have occurred, they are classified into three types: L (countless), M (many), and S (few). You may evaluate by M and S.

The evaluation tests consisted of two types of evaluation tests, an example that is an example of the tire testing method according to the present invention and a comparative example that is a tire testing method to be compared with the tire testing method according to the present invention. It was carried out by comparing it with an actual vehicle example that was used by attaching it to.

Of these, in the comparative example, the pneumatic tire 100 is exposed to ozone, but no load is applied to the pneumatic tire 100 . On the other hand, in an example, which is an example of the tire testing method according to the present invention, a test was performed in which the pneumatic tire 100 was exposed to ozone and a load was applied to the pneumatic tire 100 . In this example, the load applied to the pneumatic tire 100 was 60% of the maximum load capacity of the pneumatic tire 100 .

As a result of conducting the evaluation test of the tire test method as described above, as shown in FIG. It was found that the number of groove cracks generated was close to that of the actual vehicle. That is, the tire testing method according to the example can improve market reproducibility of groove cracks.

REFERENCE SIGNS LIST 1 tire test device 10 test chamber 20 air conditioner 25 temperature sensor 30 ozone supply device 35 ozone concentration sensor 40 load mechanism device 41 flat spot generator 42 ground surface plate 43 contact surface 44 strut 46 restraint member 47 connection member 50 load sensor 100 air Inner tire 101 Tread contact surface 102 Groove 110 Rim wheel

Claims (7)

By stopping the rotation of the pneumatic tire while exposing the pneumatic tire to ozone in an atmosphere adjusted to a predetermined temperature, the pneumatic tire in the tire circumferential direction The position is the same position, a load is applied in a direction orthogonal to the tire width direction of the pneumatic tire ,
A tire testing method, characterized in that the internal pressure of the pneumatic tire is reduced with the lapse of time during which the load is applied to the pneumatic tire . The tire testing method according to claim 1, wherein the load applied to the pneumatic tire is within a range of 40% or more and 100% or less of the maximum load capacity of the pneumatic tire. The tire testing method according to claim 1 or 2, wherein the concentration of said ozone that exposes said pneumatic tire is within the range of 50 pphm or more and 250 pphm or less. The tire testing method according to any one of claims 1 to 3, wherein the temperature of the atmosphere is in the range of 30°C or higher and 70°C or lower. The tire testing method according to any one of claims 1 to 4, wherein the pneumatic tire has an internal pressure within a range of 60% or more and 100% or less of the maximum air pressure of the pneumatic tire. The tire testing method according to any one of claims 1 to 5 , wherein the temperature of the atmosphere is changed while the load is continuously applied to the pneumatic tire. an air conditioner capable of adjusting the temperature in the test chamber to a predetermined temperature;
an ozone supply device capable of supplying ozone into the test chamber;
By stopping the rotation of the pneumatic tire in the test chamber, the position of the pneumatic tire in the tire circumferential direction is the same position, and the position of the pneumatic tire in the direction perpendicular to the tire width direction a load mechanism device that loads a load;
with
The load mechanism device is
a contact surface of the ground surface plate that contacts the tread contact surface of the pneumatic tire;
a pillar erected on the ground surface plate and having two pillars arranged at an interval wider than the width of the pneumatic tire in the tire width direction;
It is connected to the rim wheel attached to the pneumatic tire and the two pillars, and can change the distance from the contact surface by moving relative to the pillars in the extending direction of the pillars. a connecting member;
A tire testing device , wherein a load is applied to the pneumatic tire by changing the distance between the connecting member and the contact surface .

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