JP6215007B2 - Wear evaluation method and wear tester for tire rubber - Google Patents

Description

  The present invention relates to a tire rubber wear evaluation method and a wear tester.

  As a method for evaluating the wear of rubber used in a tire tread, a method is known in which a cylindrical rubber sample S made of rubber to be evaluated is pressed against a rotating surface with a constant contact pressure to be worn. Conventionally, the contact pressure is an arbitrarily selected contact pressure, not considering the actual contact pressure between the tire mounted on the actual vehicle and the road surface. Further, the roughness of the rotating surface was not arbitrarily determined considering the actual road surface roughness, but arbitrarily selected roughness. As described above, since the wear evaluation is performed under conditions different from the actual use conditions of the tire, the wear evaluation result lacks reliability. For example, each rubber sample S was made of different types of rubber and the wear evaluation was performed. As a result, although the evaluation result of a certain rubber sample S was the best, the wear evaluation result of a tire made of the rubber was It was happening that it was worse than the evaluation results of other tires.

  On the other hand, in the rubber wear evaluation, there is an example in which a pressure acting on a tire of an actual vehicle is obtained and the pressure is applied to a rubber test piece (Patent Document 1). Further, in wear evaluation using an actual tire, it has been proposed to reproduce an actual road surface using aggregate (Patent Document 2). Also, in terms of wear due to rubber road surface, microroughness (roughness of asphalt or the like in which aggregates are embedded) is more than macro roughness (roughness due to aggregates such as pebbles that form the road surface). The research result that it influences is reported (nonpatent literature 1).

JP 2008-185475 A JP-A-7-20030

THE EFFECT OF ROAD SURFACE TETURE ON TIRE WEAR, R. W. Lowne, Wear 15 (1970)

  The problem to be solved by the present invention is to provide a highly reliable wear evaluation method and wear tester.

The tire rubber wear evaluation method of the embodiment is a tire rubber wear evaluation method in which a main test load is applied to a rubber sample to press the rubber sample against the rotating surface of the rotating body, and the rubber sample is worn. A step of measuring a contact pressure between a tire mounted on an actual vehicle and a road surface, and a main test applied to the rubber sample such that a contact pressure between the rubber sample and the rotating surface is equal to the measured contact pressure. The step of determining a load, the step of taking road surface unevenness data, the step of determining the surface roughness of the rotating surface based on the obtained road surface unevenness data, and the rotating surface being determined as described above a step of the surface roughness, the rubber samples over the present test load determined in includes a step of pressing the rotating surface of the rotating surface, based on the data of unevenness of the of the resulting road surface The step of determining the surface roughness is obtained by decomposing the obtained line representing the road surface irregularities into a plurality of waves having different wavelengths, and adding a wave having a wavelength shorter than a predetermined length of the plurality of waves to the surface roughness. The method includes calculating a thickness and setting the surface roughness of the rotating surface .

  The tire rubber wear evaluation method of the embodiment is highly reliable.

(A) The partial top view of the wear test machine 1 of a turntable type | mold. (B) The front view. FIG. 3 is a partial front view of the drum-type wear tester 2. (A) The graph which shows the relationship between the pre-test load concerning the rubber sample S, and the contact area of the rubber sample S and a contact surface. (B) The graph which shows the relationship between the pre-test load concerning the rubber sample S, and the contact pressure of the rubber sample S and a contact surface. Sectional drawing of a road surface. (A) A waveform representing the measured unevenness of the road surface. (B) A plurality of waves having different wavelengths that approximate the waveform of (a). (C) Waveform after cut-off. (A) The graph of the evaluation result of the comparative example 1. (B) The graph of the evaluation result of the comparative example 2. (C) The graph of the evaluation result of an Example.

(1) Rubber Wear Tester In the rubber wear evaluation method of the embodiment, evaluation is performed on a rubber sample S in which a rubber to be evaluated is molded. The rubber sample S is formed into a cylindrical shape, and a hole for inserting a rotating shaft is formed in a cylindrical shaft portion.

  As a wear tester used for the rubber wear evaluation method of the embodiment, for example, there is a turntable wear tester 1 shown in FIG. The turntable wear tester 1 includes a turntable 10 as a rotating body and a holding device 11 that presses the rubber sample S against the turntable 10.

  The turntable 10 is rotated while being kept horizontal by a drive device for the turntable 10. The upper surface of the turntable 10 becomes a rotating surface 13 against which the rubber sample S is pressed. Alternatively, a member that becomes the rotation surface 13 is attached to the upper surface of the turntable 10.

  A holding device 11 that holds the rubber sample S is provided above the turntable 10. The holding device 11 has a rotation shaft 12 that is held horizontally and perpendicular to the rotation direction of the turntable 10. The rubber sample S is held by the holding device 11 when the rotating shaft 12 is fitted in the hole of the shaft portion of the rubber sample S in a non-slidable state. The rotating shaft 12 is rotated in a direction symmetrical to the rotating direction of the turntable 10 by a driving device for the rotating shaft 12 provided in a part of the holding device 11. Thereby, the rubber sample S can rotate in a direction symmetrical to the rotation direction of the turntable 10.

  The holding device 11 can be displaced up and down and presses the rubber sample S against the rotating surface 13 of the turntable 10 when displaced downward. The holding device 11 can apply a load to the rubber sample S in a state where the rubber sample S is pressed against the rotating surface 13. The magnitude of the load can be specified by inputting from an input unit (not shown). The abrasion testing machine 1 is provided with a control unit, and the control unit controls the holding device 11 so that the load input from the input unit is applied to the rubber sample S.

  As another wear tester, the tester shown in FIG. 2 is a drum-type wear tester 2. The drum-type wear tester 2 includes a drum 20 as a rotating body. The rubber sample S is pressed against the outer peripheral surface of the drum 20 with a constant contact pressure while rotating.

  In the following description, it is assumed that the turntable type wear tester 1 is used for wear evaluation.

(2) Rubber Wear Evaluation Method In the wear evaluation method according to the present embodiment, a load is applied to the rubber sample S held by the holding device 11 (this load is referred to as “main test load”). The rubber sample S is pressed against the rotating surface 13 of the turntable 10 to evaluate the amount of wear. As the previous step, the main test load applied to the rubber sample S and the surface roughness of the rotating surface 13 are determined.

(2-1) Method for Determining Main Test Load Applied to Rubber Sample S First, the contact pressure between the tire mounted on the actual vehicle and the road surface is measured. Although the measuring method of a ground pressure is not limited, The example is demonstrated below. First, tires are mounted on the actual vehicle. And the load concerning one tire is calculated | required by calculation with the weight of a real vehicle. Next, apply ink to the tires and place the actual vehicle on paper. Then, the tire tread pattern is attached to the paper. The area of the colored portion of the pattern on the paper is the contact area between the tire and the road surface. The area of the tread groove portion (the portion that does not appear as a colored portion on the paper) is not included in the contact area between the tire and the road surface. Next, the load applied to one tire is divided by the contact area between the tire and the road surface to determine the contact pressure between the tire and the road surface.

  Next, the rubber sample S is pressed against the prepared contact surface, and the relationship between the load applied to the rubber sample S (the load applied here is referred to as “pre-test load”) and the contact pressure between the rubber sample S and the contact surface is obtained. . The method will be described below. First, prepare a flat contact surface. Any contact surface may be used, for example, the rotation surface 13 of the turntable 10. Further, paper may be laid on a flat surface, and the upper surface of the paper may be used as the contact surface. Next, ink is applied to the rubber sample S, placed on the contact surface, and a pre-test load is applied from above. Then, the contact mark of the rubber sample S is attached to the contact surface. The area of the contact mark is the contact area between the rubber sample S and the contact surface. Next, the applied pre-test load is divided by the contact area to determine the contact pressure between the rubber sample S and the contact surface. In this way, the relationship between the pre-test load applied to the rubber sample S and the contact pressure between the rubber sample S and the contact surface is obtained. Thereafter, the contact pressure between the rubber sample S and the contact surface is obtained each time the magnitude of the pre-test load applied to the rubber sample S is changed a plurality of times. In addition, the contact area between the rubber sample S and the contact surface is first examined while changing the magnitude of the pretest load a plurality of times (in this case, the graph illustrated in FIG. 3A is obtained), and then each pretest load is obtained. The contact pressure between the rubber sample S and the contact surface corresponding to may be obtained by calculation. Finally, a graph showing the relationship between the pre-test load applied to the rubber sample S and the contact pressure between the rubber sample S and the contact surface as illustrated in FIG. 3B is completed. Each point of the graph is approximated by a straight line or the like.

  Finally, from this graph, the pre-test load applied to the rubber sample S when the contact pressure between the rubber sample S and the contact surface is equal to the previously determined contact pressure between the tire and the road surface is read. The pre-test load in this case shall be the main test load. In this step, the contact pressure between the rubber sample S and the contact surface and the contact pressure between the tire and the road surface may not be completely matched. Between the two, a difference that does not significantly affect the wear evaluation result is allowed. For example, there may be a difference of 10% of the ground pressure between the tire and the road surface between the two.

(2-2) Method for Determining Surface Roughness of Rotating Surface 13 First, data on unevenness of a road surface on which a vehicle equipped with tires travels is taken. There are various types of road surfaces. Here, as an example, a road surface in which an aggregate 3 such as pebbles is fixed by an asphalt 30 as shown in FIG. 4 is assumed. For example, a general surface roughness meter or a non-contact microscope is used for the measurement. The data obtained by this measurement is data representing the unevenness of the road surface, in other words, the position in the measurement direction and the road surface height at that position, the horizontal axis is the position, and the vertical axis is the road surface height. If expressed, it is expressed as a line as illustrated in FIG. This line represents the unevenness due to the aggregate 3, the unevenness on the surface of the asphalt 30, and the like. The unevenness due to the aggregate 3 is expressed as rough unevenness, and the unevenness on the surface of the asphalt 30 is expressed as fine unevenness in the line.

  Next, a cut-off is performed on the data representing the road surface unevenness. Specifically: If a line representing the road surface unevenness shown in FIG. 5A is captured as a waveform, as shown in FIG. 5B, the waveform can be decomposed into a plurality of waves having different wavelengths. In other words, the waveform representing the road surface unevenness can be approximated by a plurality of waves having different wavelengths. Here, the longer the wave, the closer the waveform due to large unevenness of the aggregate 3 or the like. On the other hand, as the wave has a shorter wavelength, the waveform due to fine unevenness such as the unevenness on the surface of the asphalt 30 is approximated. A wave having a wavelength longer than a predetermined length is removed from the plurality of waves having different wavelengths. Here, the specific numerical value of the predetermined length is not limited, but is preferably a numerical value that can remove a wave that approximates the waveform of the aggregate 3. Then, the remaining wave, that is, a wave having a wavelength shorter than a predetermined length is added to draw a new waveform. Then, the waveform shown in FIG. 5C is obtained. This waveform is a waveform mainly due to fine irregularities such as irregularities on the surface of the asphalt 30. Data indicating this waveform is data after cut-off.

  Next, the surface roughness is obtained from the data after cut-off. As the surface roughness obtained here, there can be various ones such as arithmetic average roughness and ten-point average roughness.

  The surface roughness obtained as described above is defined as the surface roughness of the rotating surface 13.

(2-3) Implementation of test The surface roughness of the rotating surface 13 is the surface roughness determined by the above method. Although the method is not limited, for example, a safety walk having the same surface roughness as the surface roughness determined by the above method is attached to the upper surface of the turntable 10 to form the rotating surface 13. Here, the safety walk is a predetermined surface roughness obtained by attaching abrasive grains to the surface of the cloth with glue or the like.

  Next, the rubber sample S is held by the holding device 11. Further, the main test load determined by the above method is input to the input unit of the wear tester 1.

  Next, rotation of the turntable 10 is started, the holding device 11 is displaced downward, and the rubber sample S is pressed against the rotation surface 13. At this time, the main test load input to the input unit is applied to the rubber sample S under the control of the control unit.

  Then, when predetermined time passes, rotation of the turntable 10 will stop and the holding | maintenance apparatus 11 will be displaced upwards. The rubber sample S is removed from the holding device 11, and the wear amount and the like are examined.

(3) Effect According to the tire rubber wear evaluation method of the present embodiment, a contact pressure of the same magnitude as the contact pressure between the tire mounted on the actual vehicle and the road surface can be applied to the rubber sample S. Furthermore, the rubber sample S can be worn on the rotating surface 13 having the surface roughness determined based on the surface roughness of the road surface. Therefore, the rubber sample S can be worn under conditions close to the actual wear conditions of the tire. Therefore, the reliability of wear evaluation is increased.

  In particular, a cut-off is performed on the data representing the unevenness of the measured road surface, and the surface roughness obtained from the data after the cut-off is used as the surface roughness of the rotation surface 13. Roughness close to micro-roughness that affects wear can be achieved. Therefore, the reliability of wear evaluation is increased. Further, since it is not necessary to reproduce the macro roughness having a small influence on the rubber wear when the rotating surface 13 is processed, the number of processing steps is reduced. In particular, when the wave that approximates the waveform of the aggregate 3 is removed by the cut-off, the surface roughness of the rotating surface 13 can be made closer to a microroughness, so that these effects are remarkable. Become.

(4) Example The accuracy of the wear evaluation method of the above embodiment was examined. Specifically, a tire and a rubber sample S are made from three types of rubber, and the wear evaluation of a tire mounted on an actual vehicle, the wear evaluation of the rubber sample S performed by the method of the comparative example described below, and the method of the above embodiment The wear evaluation of the rubber sample S performed in (Method of Example) was performed, and the results were indexed. Here, an index of the tire wear evaluation result is an actual vehicle wear index, and an index of the rubber sample S wear evaluation result is a laboratory wear index. Then, the correlation coefficient between the actual vehicle wear index and the lab wear index of the example is obtained, and the correlation coefficient between the actual vehicle wear index and the lab wear index of the comparative example is obtained, and these correlation coefficients are compared. We investigated which correlation was strong.

  Specifically, first, a tire and a rubber sample S were manufactured using three types of rubbers with different types and amounts of compounding agents.

  Next, the manufactured tire was mounted on a four-wheel actual vehicle, and the amount of wear was evaluated. Here, all the tires of the four wheels were the same type. Since there are three types of tires for each type of rubber, every time the evaluation is completed, the tires are all replaced with different types, and all types of tires are evaluated. The size of the tire used for evaluation is 195 / 65R15. The internal pressure of the tire is 230 kPa.

  Further, the wear amount of three types of rubber samples S having different types of rubber was evaluated using a wear tester. The evaluation methods are those of Comparative Example 1, Comparative Example 2, and Examples below.

  The evaluation method of Comparative Example 1 is an evaluation method that has been conventionally performed. Specifically, this is an evaluation method for arbitrarily determining the load applied to the rubber sample S and the surface roughness of the rotating surface 13. Here, the load applied to the rubber sample S was set to such a magnitude that the contact pressure between the rubber sample S and the rotating surface 13 was 300 kPa. The rotating surface 13 was a safety walk to which 240 mesh abrasive grains were glued.

  The evaluation method of Comparative Example 2 is an evaluation method in which the load applied to the rubber sample S is determined by the method of the above embodiment, and the surface roughness of the rotating surface 13 is arbitrarily determined. As a result of determining the load applied to the rubber sample S by the method of the above embodiment, the contact pressure between the rubber sample S and the rotating surface 13 became 230 kPa. The rotating surface 13 was a safety walk to which 240 mesh abrasive grains were glued.

  The evaluation method of an Example is the evaluation method of said embodiment. As a result of determining the load applied to the rubber sample S by the method of the above embodiment, the contact pressure between the rubber sample S and the rotating surface 13 became 230 kPa. The surface roughness of the rotating surface 13 was also determined by the method of the above embodiment, and the rotating surface 13 was used as a safety walk for the surface roughness.

  Except for the items described above, the detailed conditions of the evaluation method and the structure of the testing machine used for evaluation are the same in Comparative Example 1, Comparative Example 2, and Examples.

  The evaluation results are expressed as indexes, and the actual vehicle wear index for each rubber is plotted on the vertical axis, and the laboratory wear index is plotted on the horizontal axis in FIGS. 6 (a) to 6 (c). Table 1 shows the obtained correlation coefficients.

  The correlation coefficient was close to 1 in the order of Example, Comparative Example 2, and Comparative Example 1, and the correlation was strong. From this, it was confirmed that according to the evaluation method of the above-described embodiment, the quality of the tire wear state due to the difference in the type of rubber can be best reproduced. Therefore, it was confirmed that the evaluation method of the above embodiment has high reliability.

(5) Modification Example (5-1) Modification Example 1 of Wear Tester
The actual test load applied to the rubber sample S may be automatically determined by a wear tester. For example, the wear tester may have the following configuration. First, an actual contact pressure input unit is provided for inputting the contact pressure between the tire mounted on the actual vehicle and the road surface. Further, a pre-test result input unit is provided for inputting a pre-test load applied to the rubber sample S and a contact area between the rubber sample S and the contact surface when the rubber sample S is pressed against the prepared contact surface. Yes. Furthermore, based on the input value from the previous test result input unit, the relationship between the previous test load applied to the rubber sample S and the contact pressure between the rubber sample S and the contact surface is obtained by the method shown in (2-1). A test load determination unit is provided. This test load determination unit is the method shown in (2-1), so that the contact pressure with the rotating surface 13 of the rubber sample S is equal to the ground pressure input from the measured ground pressure input unit. Determine the actual test load on S. Furthermore, a control unit that controls the holding device 11 so as to apply the determined final test load to the rubber sample S is also provided.

  The evaluator inputs the contact pressure between the tire mounted on the actual vehicle and the road surface to the measured contact pressure input unit. Further, the pre-test load applied to the rubber sample S and the contact area between the rubber sample S and the contact surface when the rubber sample S is pressed against the prepared contact surface are input to the pre-test result input unit. Then, the main test load determination unit performs data processing to determine the main test load, and the control unit controls the holding device 11 so that the main test load is applied to the rubber sample S.

  If the wear tester has such a configuration, the test load is automatically determined, so that the labor of the evaluator can be saved.

(5-2) Modification 2 of the wear tester
The surface roughness of the rotating surface 13 may be automatically determined by a wear tester. For example, the wear tester may have the following configuration. First, a road surface surface roughness input unit for inputting measured road surface unevenness data is provided. In addition, a surface roughness determination unit that performs the cutoff described in (2-2) on the input data and obtains the surface roughness from the data after the cutoff is provided. Further, a display unit for displaying the obtained surface roughness is provided.

  The evaluator inputs the measured road surface unevenness data to the input unit. Then, the surface roughness determination unit performs data processing. The obtained surface roughness is displayed on the display unit. The evaluator looks at it and sets the surface roughness of the rotating surface 13 as the surface roughness displayed on the display unit.

  If the wear tester has such a configuration, the surface roughness of the rotating surface 13 is automatically determined, so that the labor of the evaluator can be saved.

  Also, a plurality of types of rotating bodies such as the turntable 10 in which the rotating surface 13 has been processed in advance to a predetermined surface roughness may be prepared for each surface roughness. And when the surface roughness of the rotating surface 13 is determined by the above method, the rotating body having the surface roughness of the rotating surface 13 may be configured to come out at the rotating position.

(5-3) Modification Example of Determination Method of the Test Load Applied to the Rubber Sample S The test load applied to the rubber sample S is such that the contact pressure between the rubber sample S and the rotating surface 13 is the tire mounted on the actual vehicle and the road surface. And is not limited to the method of the above embodiment. For example, in determining the relationship between the pre-test load applied to the rubber sample S and the contact pressure between the rubber sample S and the contact surface, the contact pressure may be directly measured using pressure sensitive paper or the like. If the contact pressure is measured directly, it is possible to save the calculation effort as in the case of the above embodiment.

(5-4) Modification Example of Method for Determining Surface Roughness of Rotating Surface 13 The surface roughness of the rotating surface 13 only needs to be determined based on actual road surface unevenness data. The general method is not limited to the method of the above embodiment. For example, the surface roughness of the rotating surface 13 may be obtained by obtaining the surface roughness from the data as it is without performing data processing such as cutoff on the road surface unevenness data. In this case, the labor of data processing can be saved.

S ... rubber sample, 1 ... turntable type wear tester, 10 ... turntable, 11 ... holding device, 12 ... rotating shaft, 13 ... rotating surface, 2 ... drum type wear tester, 20 ... drum, 3 ... Aggregate, 30 ... asphalt

Claims (2)

A method for evaluating the wear of a tire rubber in which the rubber sample is pressed against a rotating surface of a rotating body by applying a main test load to the rubber sample, and the rubber sample is worn.
Measuring the contact pressure between the tire mounted on the actual vehicle and the road surface;
Determining a final test load applied to the rubber sample such that a contact pressure of the rubber sample with the rotating surface is equal to the measured ground pressure;
A process of taking data on road surface irregularities,
Based on the obtained road surface irregularity data, determining the surface roughness of the rotating surface;
Setting the rotating surface to the determined surface roughness;
Applying the determined final test load to the rubber sample and pressing the rubber sample against the rotating surface .
The step of determining the surface roughness of the rotating surface based on the obtained road surface unevenness data,
The obtained road surface irregularities are decomposed into a plurality of waves having different wavelengths, and the surface roughness is calculated from a line formed by adding a wave having a wavelength shorter than a predetermined length among the plurality of waves. Including the step of surface roughness,
A method for evaluating wear of rubber for tires. The step of determining the main test load includes:
Applying a plurality of different pre-test loads to the rubber sample and pressing them against the contact surface, and determining the relationship between the pre-test load and the contact pressure between the rubber sample and the contact surface;
From the relationship between the obtained pre-test load and the contact pressure, the rubber sample for making the contact pressure between the rubber sample and the rotating surface equal to the measured contact pressure between the tire and the road surface Determining the actual test load to be applied;
The tire rubber wear evaluation method according to claim 1, comprising:

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