JP6088376B2 - Tire wear resistance evaluation method - Google Patents

Description

  The present invention relates to a method for evaluating the wear resistance performance of a tire in which a tread rubber disposed on a contact surface of a tread portion is formed by a so-called strip wind method.

  The tread portion of the tire includes a tread rubber disposed on the contact surface side. As the tread rubber, for example, one formed by a strip wind method is known. In the strip winding method, for example, a raw tread rubber is formed by spirally winding a strip-shaped rubber strip having a width of about 5 to 30 mm on the outer side of a cylindrical body to be wound in the tire circumferential direction. . This raw tread rubber is integrated by vulcanization. The tread rubber formed in this way includes an interface between adjacent rubber strips in the tread width direction. The interface extends in the tire circumferential direction on the surface of the tread rubber.

JP 2012-116246 A

  When the tire is actually mounted on a vehicle and used for a long time, the contact surface of the tread rubber is worn. At this time, for example, if there is a problem in the rubber composition or winding condition of the tread rubber, the ground contact surface of the worn tread rubber may cause a stripe-like damage in which the interface portion is locally worn or peeled off. is there. Such damage could not be confirmed unless, for example, the tire was actually used. For this reason, there has been a strong demand for a method capable of appropriately evaluating the wear resistance of the tread rubber formed by the strip wind method in a short period of time.

  The present invention has been made in view of the above problems, and has as its main object to provide a method capable of appropriately evaluating the wear resistance characteristic of a tread rubber formed by a strip wind method in a short period of time.

  Of the present invention, the invention according to claim 1 is characterized in that the tread rubber disposed on the contact surface of the tread portion has a wear resistance performance of a tire formed by winding a belt-shaped rubber strip spirally in the tire circumferential direction. A method for evaluating, comprising: a wear process for wearing the tread rubber; and an evaluation process for observing and evaluating the wear status of the tread rubber after the wear process, wherein the wear process includes the tire The first wear process for turning the vehicle equipped with a circle on a dry road surface and the second wear process for turning the vehicle equipped with the tire on a wet road surface are set as one set, and this set is performed a plurality of times. This is a method for evaluating the wear resistance performance of a tire characterized by the following.

  According to a second aspect of the present invention, the vehicle is a four-wheeled vehicle, and the tire is mounted on a wheel on the outer side of the four-wheeled vehicle during a circular turn. It is an evaluation method.

  The invention according to claim 3 is the tire wear resistance evaluation method according to claim 2, wherein the circular turning gives a lateral acceleration of 0.4 to 0.6 G to the vehicle.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the circular turning in the second wear step gives the vehicle a higher lateral acceleration than the circular turn in the first wear step. This is a method for evaluating the wear resistance performance of tires.

  The method for evaluating the wear resistance performance of a tire according to the present invention includes a wear process for wearing a tread rubber, and an evaluation process for observing and evaluating the wear state of the tread rubber after the wear process. The wear process includes one set of a first wear process for turning the vehicle with the tire mounted on a dry road surface and a second wear process for rotating the vehicle with the tire mounted on a wet road surface. The set is performed multiple times.

  In the wear process, the vehicle is turned on a dry road surface and a wet road surface. As a result of various experiments, when the tread rubber made by the strip wind method is circularly swung, a lateral force acts on the interface of the rubber strip almost at right angles, and the damage on the interface is locally accelerated. In addition, by alternately performing this circular turning on the dry road surface (high μ) and the wet road surface (low μ), damage to the interface can be prevented while preventing wear of the tread rubber and promoting overall wear. It was found that it can be accelerated and expressed. Therefore, a tire in a state close to actual wear is reproduced in a shorter period.

  As described above, in the tire wear resistance performance evaluation method of the present invention, in the wear process, when the tire has a problem such as rubber blending or winding conditions, streak damage along the tread rubber interface is early. Can be expressed. Therefore, according to the present invention, it is possible to evaluate the suitability of the wear resistance characteristic of the tread rubber formed by the strip wind method.

It is meridian sectional drawing of the tire for evaluation of this embodiment. It is a perspective view of the unvulcanized tire in a manufacturing process. It is the expanded view by which the tread part was expand | deployed. It is a flowchart which shows the procedure of the evaluation method of this embodiment. It is a flowchart which shows the procedure of the abrasion process of an evaluation method. It is the expanded view by which the tread part after an abrasion process was expand | deployed.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a meridian cross section including the tire rotation axis of the tire T evaluated by the wear resistance performance evaluation method of the present embodiment. As shown in FIG. 1, the tire T is disposed, for example, on the carcass 6 that extends from the tread portion 2 through the sidewall portion 3 to the bead portion 4, and on the outside of the carcass 6 in the tire radial direction and inside the tread portion 2. Belt layer 7. The tire T may include, for example, a band layer (not shown) disposed outside the tire radius of the belt layer 7. In the present embodiment, tires for passenger cars are shown as such tires T, but it is needless to say that tires of various categories such as motorcycles and heavy loads are included.

  The tire T includes a tread rubber TG disposed on the contact surface side in the tread portion 2, a sidewall rubber SG disposed on the tire axial direction outer side in the sidewall portion 3, and an inner liner rubber disposed on the tire lumen surface 8 side. Includes IG and others.

  The “landing surface” means that when the normal tire T, which is assembled to a normal rim and filled with a normal internal pressure, is loaded with a normal load and brought into contact with a flat surface at a camber angle of 0 °, the plane This is the part that contacts the ground.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire T is based. For example, “Standard Rim” for JATMA and “Design Rim” for TRA. "If it is ETRTO, it is" Measuring Rim ".

  The “regular internal pressure” is the air pressure defined by each standard for each tire in the standard system including the standard on which the tire T is based. For example, “maximum air pressure” for JATMA, and table for TRA. The maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO.

  The “regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire T is based. For example, “maximum load capacity” for JATMA and “TRA” for TRA. The maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", "LOAD CAPACITY" for ETRTO.

  The tire T is formed by vulcanizing an unvulcanized raw tire.

  FIG. 2 shows a schematic perspective view of the manufacturing process of the tread rubber TG used for the raw tire. As shown in FIG. 1 or FIG. 2, the tread rubber TG is formed by a strip wind method. In the strip wind method, for example, an annular tread rubber TG is formed by spirally winding a non-vulcanized rubber strip Ga having a belt shape around a cylindrical body to be wound G in the tire circumferential direction.

  The rubber strip Ga is continuously extruded by, for example, an extrusion device (not shown). The rubber strip Ga of this embodiment is, for example, a belt shape having a width of about 5 to 30 mm.

  As can be seen from FIG. 2, the tread rubber TG formed by the strip wind method includes an interface S that forms a boundary between the rubber strips Ga and Ga adjacent in the tire axial direction. The interface S continuously appears in the tire circumferential direction along the rubber strip Ga on the outer surface of the tread rubber TG. The tread rubber TG formed in an annular shape is removed from the body G to be wound, and is incorporated into the green tire according to the custom. Thereafter, the raw tire is vulcanized.

  FIG. 3 shows a developed view in which the tread portion 2 of the vulcanized tire T is developed. By vulcanization, the rubber strips Ga of the tread rubber TG are integrally joined to each other. In such a tire Ta, it is very difficult to observe the interface S of the rubber strip Ga on the ground contact surface of the tread portion 2 with, for example, the naked eye.

  As shown in FIG. 3, for example, a plurality of main grooves 10 extending continuously in the tire circumferential direction and a plurality of lateral grooves 11 extending from each main groove 10 are formed on the ground contact surface of the tread portion 2 of the present embodiment. Is provided. The main groove 10 includes, for example, a pair of crown main grooves 10a extending on both sides of the tire equator C and a pair of shoulder main grooves 10b extending most outward in the tire axial direction. The tread pattern is not an essential component of the present invention.

  FIG. 4 is a flowchart showing an example of the procedure of the method for evaluating the wear resistance performance of the tire T according to this embodiment. As shown in FIG. 4, the evaluation method of the present embodiment includes a wear process S1 for wearing the tread rubber TG of the tire T, and an evaluation process for observing and evaluating the wear situation of the tread rubber TG after the wear process S1. S2 is included.

  FIG. 5 is a flowchart showing an example of a specific procedure of the wear process S1. As shown in FIG. 5, in the wear process S <b> 1, for example, a first wear process S <b> 11 is performed in which a vehicle (not shown) on which a tire T is mounted is circularly turned on a dry road surface.

  In the first wear process S11, a vehicle is first prepared. In the present embodiment, for example, a four-wheeled vehicle is used as the vehicle. For example, in a four-wheeled vehicle, the tire T is preferably attached to a wheel that is on the outside during a circular turn. Thereby, the tread rubber TG can be efficiently worn during the circular turning of the vehicle.

  The dry road surface in the first wear process S11 is, for example, an asphalt road surface that is not wet. In the first wear step S11, it is desirable to turn the vehicle at a high speed along a circle having a radius of about 50 m, for example, on such a dry road surface.

  In the first wear step S11, lateral acceleration is given to the vehicle during the circular turning of the vehicle. Thereby, the tread rubber TG receives a lateral force along the tire axial direction and wears. When the lateral acceleration is small, the time required to wear the tread rubber TG may increase. On the other hand, when the lateral acceleration is large, there is a possibility that each land portion such as a block, which is divided by the main groove 10 and the lateral groove 11 on the ground contact surface, is chipped and the tire T cannot run. From such a viewpoint, in the first wear step S11, it is desirable to give a lateral acceleration of about 0.4 to 0.6 G to the vehicle, for example, during the circular turning of the vehicle.

  In the first wear step S11, it is desirable that the vehicle travels, for example, about 1000 to 2000 m during the circular turn. If the travel distance is less than 1000 m, the tread rubber TG may not be sufficiently worn. Conversely, when the travel distance is greater than 2000 m, the amount of travel wear once on the dry road surface increases, and the tread rubber TG may wear rapidly and distorted.

  Next, in the wear process S1, a second wear process S12 for turning the vehicle on a wet road surface is performed. In the second wear process S12, the vehicle turned in the first wear process S11 is used to make a circular turn on the wet road surface.

  The wet road surface in the second wear step S12 is preferably a so-called skid pad including a water film formed by water discharge on the surface of the asphalt road surface, for example. In the second wear step S12, it is desirable to turn the vehicle at a high speed along a circle having a radius of about 50 m, for example, on such a wet road surface.

  Even in the second wear step S12, a lateral acceleration is applied to the vehicle during a circular turn. From the same viewpoint as the circular turning on the dry road surface, in the second wear step S12, it is desirable to give the vehicle a lateral acceleration of about 0.4 to 0.6 G, for example, in the circular turning of the vehicle.

  In the second wear step S12, from the same viewpoint as the circular turning on the dry road surface, it is desirable to drive the vehicle, for example, about 1000 to 2000 m in the circular turning.

  In wear process S1, 1st wear process S11 and 2nd wear process S12 are made into 1 set, and this set is performed in multiple times. It is desirable that the number of sets is performed by a preset number of sets based on, for example, various experimental data.

  FIG. 6 shows a developed view in which the tread portion 2 after the wear process S1 is developed. As shown in FIG. 6, for example, when the tread rubber TG has a problem such as rubber blending, the tire T has a muscle that is locally worn or peeled along the interface S on the interface S of the worn tread rubber TG. -Like damage P may occur.

  In the evaluation method of the present embodiment, a substantially vertical lateral force is applied to the interface S of the rubber strip Ga of the tread rubber TG by turning the vehicle in the wear step S1. Moreover, in the wear step S1, the vehicle is alternately turned on a dry road surface having a relatively high dynamic friction coefficient μ and a wet road surface having a relatively low dynamic friction coefficient μ. For this reason, the surface of the tread rubber TG is rough and the entire surface is greatly worn by running on the dry road surface, while the unevenness on the surface of the tread rubber TG is flattened by running on the wet road surface. Thus, the tread rubber TG can be worn by the wear of different properties. Therefore, in the evaluation method of the present embodiment, the formation rate of the damage P at the interface S can be further accelerated, and the time taken for the wear step S1 can be further shortened. For this reason, when there is a defect in the tread rubber TG, the formation speed of the damage P at the interface S of the tread rubber TG is accelerated, and the time required for the wear process S1 can be shortened.

  In the evaluation step S2, the tread rubber TG after the wear step S1 is observed, and the wear resistance performance of the tire T is evaluated based on the observation result. In the evaluation step S2 of the present embodiment, for example, when the tread rubber TG is observed with the naked eye of the evaluator and damage P can be confirmed on the contact surface of the tread rubber TG, the wear resistance performance of the tire T is evaluated as poor. .

  As described above, in the evaluation method of the present embodiment, in the wear step S1, when the tire T has a problem such as rubber blending or winding conditions, the streak damage P along the interface S of the tread rubber TG is preliminarily early. In the evaluation step S2, it is possible to evaluate the suitability of the wear resistance specific to the tread rubber TG formed by the strip wind method.

  In a preferred aspect of the wear step S1, it is desirable to give the vehicle a higher lateral acceleration in the circular turn in the second wear step S12 than in the circular turn in the first wear step S11. The dry road surface has a relatively large dynamic friction coefficient μ, and when a large lateral acceleration is applied to the vehicle, there is a possibility that the tread portion 2 may be missing rubber and the tire T may burst. On the other hand, the wet road surface has a relatively small dynamic friction coefficient μ and the tire T does not easily generate heat due to the water film. Therefore, even when a large lateral acceleration is applied, the wet road surface can be worn while preventing heat damage.

  In addition, when the number of repeated sets of the first wear process S11, the second wear process S12, and the w1 set is small, there is a possibility that the tread rubber TG is not damaged P even if the tread rubber TG is defective. On the contrary, when the number of sets is large, if the tread rubber TG is not defective, the tread rubber TG is not damaged P, and the time required for the wear process S1 may be increased. From such a viewpoint, as shown in FIG. 5, the wear process S <b> 1 of the present embodiment is, for example, a confirmation process S <b> 13 for visually confirming the wear state of the tread rubber TG of the tire T every time one set is completed. And the end and continuation of the wear step S1 may be determined.

  In the tread portion 2 after the wear step S1, the damage P is formed more on the outer side in the tire axial direction of the contact surface, for example. For this reason, in a preferred embodiment of the evaluation step S2, for example, when the outside of the contact surface in the tire axial direction is observed and the damage P is confirmed on the tread rubber TG when the vehicle is stopped in the wear step S1, the wear resistance performance of the tire T is confirmed. May be evaluated as defective. In such an evaluation step S2, the time required for evaluating the wear resistance performance of the tire T can be significantly shortened.

  As mentioned above, although embodiment of this invention was explained in full detail, this invention is not limited to this embodiment, It can deform | transform and implement in a various aspect.

A plurality of evaluation tires that have been previously known to have been found to cause streak damage in the tire circumferential direction along the interface of the rubber strip on the contact surface of the tread rubber after long-term use. These tires were evaluated by the wear resistance performance evaluation methods of the comparative example and the example based on the specifications in Table 1, and the reproducibility of each evaluation method was evaluated.
The main common specifications and test conditions of tires are as follows.

Common specifications Tire size: 195 / 65R15
Rim size: 15 × 6.0J
Test internal pressure: 230 kPa
Test vehicle: 1800cc FR vehicle Tire mounting position: Mounted on front and rear wheels outside the turning direction Test course: Dry road surface: Asphalt road
: Wet road surface: Skid pad Each test method is as follows.

<Reproducibility>
In the above specifications and test conditions, in the evaluation method of each embodiment, one driver rides three rounds of a 50m radius circle on a dry road surface and three rounds of a 50m radius circle on a wet road surface. And after performing the said setting 10 times, the tread rubber was observed visually. In the evaluation method of each comparative example, a circular turn with a radius of 50 m was performed on a dry road surface, and after the tread rubber was sufficiently worn, the tread rubber was visually observed. After each of these wear resistance performance tests was performed five times, the rate at which each observation result obtained matched the observation result obtained by visually observing the tire tread rubber that had been damaged in actual long-term use was the reproducibility. It was evaluated by. The higher the recall, the better the wear resistance performance evaluation method.

  In Comparative Example 1 and Example 1, it has been previously determined that long-term use does not cause streak damage in the tire circumferential direction along the interface of the rubber strip on the contact surface of the tread rubber. For the tire, the above recall was similarly evaluated.

  From the test results, the wear resistance performance evaluation method of each example was found in advance to cause streak damage in the tire circumferential direction along the rubber strip interface on the tread rubber contact surface after long-term use. In the case of the tire for evaluation, it was confirmed that the reproduction rate was superior to the evaluation method for wear resistance performance of the comparative example, and the wear resistance performance of the tire could be evaluated well.

T tire TG tread rubber Ga rubber strip S1 wear process S2 evaluation process S11 first wear process S12 second wear process

Claims (4)

A tread rubber disposed on a ground contact surface of a tread portion is a method for evaluating the wear resistance performance of a tire formed by spirally winding a belt-shaped rubber strip in the tire circumferential direction,
A wear process for wearing the tread rubber;
An evaluation step of observing and evaluating the wear situation of the tread rubber after the wear step,
The wear process includes a first wear process in which a vehicle equipped with the tire is circularly turned on a dry road surface;
A tire wear resistance performance evaluation method characterized in that the second wear step of circularly turning a vehicle equipped with the tire on a wet road surface is one set, and this set is performed a plurality of times. The vehicle is a four-wheeled vehicle,
2. The tire wear resistance evaluation method according to claim 1, wherein the tire is attached to an outer wheel when the four-wheeled vehicle is in a circle.   The tire wear resistance evaluation method according to claim 2, wherein the circular turning gives a lateral acceleration of 0.4 to 0.6 G to the vehicle.   The tire wear resistance evaluation method according to any one of claims 1 to 3, wherein the circular turning in the second wear step gives the vehicle a lateral acceleration higher than the circular turn in the first wear step.

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