JP2020027041A - Method and device for determining featheredge wear of pneumatic tire - Google Patents

Abstract

To provide a method and device for determining the featheredge wear of a pneumatic tire, in which the presence of featheredge wear is accurately determined.SOLUTION: The method for determining the featheredge wear of a pneumatic tire includes: installing microphones 20, 21 at positions corresponding to both edges of portions 6-8 in a tire width direction TW; rolling a tire 1 at a prescribed speed and measuring the sound pressure of a pattern noise generated by the portions 6-8 with the microphones 20, 21; calculating a first reference energy value Ec1; calculating a second reference energy value Ec2; calculating a reference ratio Rc that is the ratio of the first reference energy value Ec1 to the second reference energy value Ec2; calculating a first measured energy value E1; calculating a second measured energy value E2; calculating a measured ratio Rm that is the ratio of the first measured energy value E1 to the second measured energy value E2; and determining that there is the occurrence of featheredge wear when the measured ratio Rm is different from the reference ratio Rc by a prescribed amount or more.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method and an apparatus for determining feather edge wear of a pneumatic tire.

  In a pneumatic tire mounted on an automobile or the like, various uneven wears occur according to a tread pattern. For example, in a tire having a portion such as a shoulder portion, a quarter portion, and a center portion extending in the tire circumferential direction divided by the circumferential groove, one of the two edges in the tire width direction of the portion has the other edge. The uneven wear may be larger than the edge. The uneven wear is referred to as feather edge wear. Since feather edge wear deteriorates tire performance, it is required to accurately detect and deal with it.

  Patent Literature 1 discloses a method of measuring a tire wear amount by measuring a sound pressure level for each frequency in a tire pattern noise and performing a comparison operation with a sound pressure level of a reference tire.

JP 2000-346755 A

  The method for measuring the amount of wear of a tire disclosed in Patent Document 1 measures general wear, and cannot measure a specific uneven wear effectively. Therefore, there is room for improvement in determining whether or not feather edge wear has occurred as specific uneven wear.

  An object of the present invention is to accurately determine whether or not feather edge wear has occurred in a method and an apparatus for determining feather edge wear of a pneumatic tire.

  According to a first aspect of the present invention, a pneumatic tire having a portion extending in a tire circumferential direction divided by at least one circumferential groove is prepared, and a pneumatic tire is provided at a position corresponding to both edges in the tire width direction of the portion. A pattern in which a first sound pressure sensor and a second sound pressure sensor are installed, and the part is generated by the first sound pressure sensor and the second sound pressure sensor by rolling the new pneumatic tire at a predetermined speed. Measuring the sound pressure of the noise, calculating a first reference energy value that is an energy value in a predetermined frequency range of the sound pressure of the new pneumatic tire measured by the first sound pressure sensor, and calculating the second sound; Calculating a second reference energy value which is an energy value of the sound pressure of the pneumatic tire in a new condition measured by a pressure sensor in the predetermined frequency range; Calculating a reference ratio that is a ratio of the second reference energy value to the reference value, and rolling the pneumatic tire at the predetermined speed to generate the portion by the first sound pressure sensor and the second sound pressure sensor. Measuring the sound pressure of the pattern noise to be caused, calculating a first measurement energy value that is an energy value of the sound pressure of the pneumatic tire measured by the first sound pressure sensor in the predetermined frequency range, and calculating the second sound. Calculating a second measured energy value which is an energy value of the sound pressure of the pneumatic tire measured by a pressure sensor in the predetermined frequency range, and measuring a ratio of the second measured energy value to the first measured energy value; Calculate the ratio, and if the measured ratio differs from the reference ratio by a predetermined amount or more, feather edge wear occurs at the site. Comprises determining a are to provide a method for determining the feather edge wear of a pneumatic tire.

  According to this method, the sound pressure of the pattern noise is measured using the first sound pressure sensor and the second sound pressure sensor respectively installed at positions corresponding to both edges in the tire width direction of the region. Therefore, it is possible to measure the sound pressure of the pattern noise generated at each of both edges in the tire width direction of the region. By comparing the ratio (measurement ratio) of the first and second measured energy values in which these sound pressures are calculated in a predetermined frequency range with the new one (reference ratio), it is possible to detect a difference in wear at both edges. . Therefore, whether or not feather edge wear has occurred can be determined based on the difference in the wear. In addition, a new article means a thing which is not used or is not worn.

  The predetermined frequency range, using the vehicle speed V corresponding to the predetermined speed, the minimum pitch length Dmin and the maximum pitch length Dmax of the block pitch in the tire circumferential direction of the tread pattern of the pneumatic tire, It may be calculated as Δf by the following equation.

  According to this method, the predetermined frequency range Δf can be specifically defined. In particular, a block having a predetermined pitch length may be formed in a portion by forming a groove extending in the tire width direction. The block is grounded at a certain time interval as the tire rotates, and generates pattern noise. Therefore, the feather edge wear can be accurately detected by adjusting the predetermined frequency range for calculating the energy to the frequency of occurrence of the pattern noise. However, the block pitch is designed to have a certain degree of variation (Dmin to Dmax) in order to prevent pattern noise from concentrating on a specific frequency. Therefore, it is effective to calculate energy not in a specific frequency point corresponding to a specific block pitch but in a predetermined frequency range corresponding to a block pitch having a variation as shown in the above equation. In addition, in the above equation, when calculating the lower limit value f1 and the upper limit value f2 of the frequency range Δf, the speed is converted to the speed per second (m / s) by multiplying the speed per hour V (km / h) by 1000/3600. The lower limit value f1 of the frequency range Δf is obtained by dividing a value obtained by converting an hourly speed V (km / h) into a second speed by a value 1.05 times the maximum pitch length Dmax. Similarly, the upper limit value f2 of the frequency range Δf is obtained by dividing a value obtained by converting the speed per hour V (km / h) to a speed per second by a value 0.95 times the minimum pitch length Dmin. The reason why the maximum pitch length Dmax is multiplied by 1.05 and the minimum pitch length Dmin is multiplied by 0.95 is to provide a margin in a frequency range for calculating an energy value.

  In the method, the block pitch is set as a primary pitch, and the predetermined frequency range is calculated at a pitch of each order according to a block division shape in the tire circumferential direction, and the order of the predetermined frequency range is calculated for each order. Calculate a reference ratio and the measurement ratio, and compare the reference ratio and the measurement ratio for each order, and when the measurement ratio is different from the reference ratio by a predetermined amount or more, feather edge wear occurs in the portion. May be determined.

  According to this method, the reference ratio and the measurement ratio are compared for each order of the pattern noise, so that a more detailed determination can be made. Specifically, if one block is divided in the tire circumferential direction by a sipe or other narrow groove, pattern noise occurs at a frequency higher than the block pitch. The high frequency pattern noise is referred to as second, third, fourth,. For example, if a block is equally divided into two in the tire circumferential direction by a sipe, a secondary pattern noise occurs. The secondary pattern noise has twice the frequency of the primary pattern noise (pattern noise due to the block pitch). Thus, by considering the order and performing the energy comparison in a more detailed unit than the block unit, the feather edge wear can be evaluated in more detail.

  In the method, it may be determined that feather edge wear has occurred at the site if the measured ratio is equal to or less than half or equal to or greater than twice the reference ratio.

  According to this method, at the time of energy comparison, the presence or absence of occurrence of feather edge wear is determined using a threshold of half or twice. This is because when the energy value of the pattern noise is half or doubled, there is a difference that can be felt by a general driver. In addition, since the threshold value is set to half or twice the energy value, even if the measured energy value changes slightly due to the influence of disturbances such as wind and road surface conditions, the occurrence of feather edge wear does not occur even if the measured value changes slightly. Can be accurately determined.

  The predetermined speed may be a speed at which the predetermined frequency range deviates from the column resonance frequency range.

  According to this method, it is possible to prevent the pattern noise from being affected by air column resonance in the circumferential groove of the tread portion of the tire. If the evaluation is performed at a speed at which the frequency range of the pattern noise coincides with the frequency range of the columnar resonance, the groove becomes shallower with each wear, so that the influence of the columnar resonance decreases. That is, the influence of columnar resonance during the evaluation is not constant. Therefore, the pattern noise can be accurately measured by setting the predetermined speed so that the predetermined frequency range deviates from the column resonance frequency range.

  In the method, the first sound pressure sensor and the second sound pressure sensor may be installed in the rolling direction of the pneumatic tire.

  According to this method, since the pattern noise appears clearly and strongly in front of the rolling direction of the tire, the sound pressure of the pattern noise can be measured efficiently. On the other hand, behind the rolling direction of the tire, the sound generated by rubbing or slipping when the tire kicks out of the ground may be mixed with the pattern noise, and the sound pressure sensor may be damaged by flying stones etc. There is also. The sound pressure of the pattern noise is often low on the side of the rolling direction of the tire. Therefore, it is preferable to measure the pattern noise ahead of the rolling direction of the tire.

  The site may be a shoulder, a quarter, or a center.

  According to this method, it is possible to determine whether or not feather edge wear has occurred in the shoulder portion, the quarter portion, or the center portion.

  According to a second aspect of the present invention, there is provided a rolling device for rolling a pneumatic tire having a portion extending in a tire circumferential direction divided by at least one circumferential groove at a predetermined speed, A first sound pressure sensor and a second sound pressure sensor which are installed at positions corresponding to the edges and measure the sound pressure of pattern noise generated when both edges of the portion are grounded; and a new pneumatic tire. A predetermined reference value of the sound pressure measured by the second sound pressure sensor when the pneumatic tire is new to a first reference energy value which is an energy value in a predetermined frequency range of the sound pressure measured by the first sound pressure sensor. A storage unit that stores a reference ratio that is a ratio of a second reference energy value that is an energy value in a frequency range of, and the sound pressure measured by the first sound pressure sensor. A first energy calculator that detects a first measured energy value that is an energy value in a fixed frequency range; and a second measured energy that is an energy value of the sound pressure measured by the second sound pressure sensor in the predetermined frequency range. A second energy calculation unit that detects a value, a measurement ratio calculation unit that calculates a measurement ratio that is a ratio of the second measurement energy value to the first measurement energy value, and a measurement ratio that is predetermined with respect to the reference ratio. A determination unit configured to determine that feather edge wear has occurred in the portion when the above-described difference is present, an apparatus for determining feather edge wear of a pneumatic tire is provided.

  According to the present invention, in a method and an apparatus for determining feather edge wear of a pneumatic tire, by comparing the sound pressure energy of pattern noise generated by each of both edges of the part with that of a new product, the feather edge is reduced. The presence or absence of wear can be determined.

The perspective view of a pneumatic tire. The development view of a part of tread pattern. The top view of the pneumatic tire which shows the installation position of a microphone. The side view of the rolling device of a pneumatic tire. The top view of the rolling device of a pneumatic tire. FIG. 3 is a block diagram of a control device. 5 is a graph showing the relationship between the frequency of pattern noise and sound pressure. The side view of the modification of the rolling device of a pneumatic tire.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  In the present embodiment, it is determined whether or not feather edge wear has occurred in the pneumatic tire. The pneumatic tire may be, for example, a general passenger car tire. Alternatively, it may be a truck or bus tire or the like. Hereinafter, a pneumatic tire is also simply referred to as a tire.

  With reference to FIG. 1, the tire 1 has a shoulder portion 6, a quarter portion 7, and a center portion 8 partitioned in the tire width direction TW by longitudinal grooves 11a to 11d extending in the tire circumferential direction TR. The shoulder portion 6, the quarter portion 7, and the center portion 8 are arranged in this order from both outer sides to the inner side in the tire width direction TW. The tire 1 rolls on a road surface while being mounted on the wheel rim 2. When the tire 1 rolls on the road surface, pattern noise corresponding to the tread pattern of the tire 1 is generated. The determination method of the present embodiment is to determine whether or not feather edge wear has occurred by measuring the pattern noise. In FIG. 1, detailed illustration of the tread pattern is omitted.

  Since the pattern noise may vary depending on the road surface condition, it is preferable to measure the pattern noise under a constant road surface condition in order to make an accurate determination. As the constant road surface condition, for example, JIS D 8301: 2013 (ISO 10844: 2011) may be adopted.

  FIG. 2 is a development view of a part of the tread portion 5 of the tire 1 (see a hatched portion in FIG. 1). The shoulder portion 6 is divided into a plurality of blocks 13 by a plurality of lateral grooves 12 extending in the tire width direction TW. In other words, the block 13 is defined by the vertical groove 11d and the horizontal groove 12.

  The blocks 13 are not formed at exactly the same pitch in the tire circumferential direction TR, but are formed at slightly different pitches. As a result, the frequency of occurrence of pattern noise is not concentrated on one frequency, and the sound pressure of one frequency is prevented from becoming extremely large. This is a design often found in general tires. Hereinafter, the formation pitch of the blocks 13 having such slight variations in the tire circumferential direction TR is also referred to as block pitch. This block pitch is represented by, for example, D1 in FIG.

  FIG. 3 is a plan view when the tire 1 is viewed from directly above, and a broken circle portion is shown in an enlarged manner. An ellipse indicated by a broken line in the center of the tire 1 indicates a ground contact area. To measure the pattern noise, a microphone (first sound pressure sensor) 20 and a microphone (second sound pressure sensor) 21 are used. The microphones 20, 21 are the same.

  Preferably, the microphones 20 and 21 are installed in the front direction Fr of the tire 1 in the rolling direction. More specifically, the microphones 20 and 21 are preferably installed in an equilateral triangular area S1 in which the width of the tire 1 is one side in a plan view or in a non-grounded area S1 'which is hidden behind the tire 1 in a plan view. This is because in the areas S1 and S1 'in front of the tire 1, large pattern noise at the moment when the block 13 touches the ground can be clearly measured. More preferably, it is arranged near the ground contact area of the tire 1 in the area S1 '.

  In the present embodiment, the microphones 20 and 21 are arranged at positions corresponding to both edges of the shoulder portion 6, the quarter portion 7 and the center portion 8 in the tire width direction TW in the vicinity of the contact region in the region S1 '. Is done. The position corresponding to both edges here means the position on the extension line from each both edges of parts 6-8 to front Fr in the tire rolling direction. The microphones 20 and 21 at both ends in the tire width direction TW may be arranged outside the regions S1 to S1 '. Others are arranged in the regions S1 to S1 '. With this arrangement, the pattern noise generated by both edges of the portions 6 to 8 can be clearly measured by the respective sound pressure sensors 20 and 21. In particular, since the two sound pressure sensors 20 and 21 are installed at different positions in one region in the tire width direction TW, it is possible to detect a difference in the wear state in one region in the tire width direction TW. That is, feather edge wear can be detected.

  Alternatively, the microphones 20 and 21 may be installed behind the tire 1 in the rolling direction. More specifically, the microphones 20 and 21 may be installed in an equilateral triangular area S2 in which the width of the tire 1 is one side in a plan view or in a non-grounded area S2 'which is hidden behind the tire 1 in a plan view. Also in this case, the microphones 20 and 21 are arranged at positions corresponding to both edges of the shoulder section 6, the quarter section 7 and the center section 8, respectively. The position corresponding to both edges here means the position on the extension line of the both edges in the tire rolling direction rearward in plan view.

  Further, in the tire height direction, the microphones 20 and 21 are preferably installed in a range from the ground to the center of the tire. Note that a member indicated by reference numeral 32 in FIG. 3 indicates a support portion 32 described later.

  In the present embodiment, a determination device for determining whether or not feather edge wear of the tire 1 has occurred is used.

  The determination device includes a rolling device 30 (see FIG. 4) for rolling the tire 1 at a predetermined speed, microphones 20 and 21 (see FIG. 3) for measuring the sound pressure of pattern noise, and a control device 40 (see FIG. 6). ) And a monitor 50 (see FIG. 6) for displaying the determination result.

  Referring to FIGS. 4 and 5, rolling device 30 includes a road surface portion 31 on which tire 1 is mounted, and a support portion 32 for supporting tire 1. The road surface section 31 includes two rollers 31a and 31b and a belt 31c. The two rollers 31a and 31b are mechanically connected to a motor (not shown). The two rollers 31a and 31b are driven to rotate in the same direction by a motor. The belt 31c is stretched over the two rollers 31a and 31b so as to surround the two rollers 31a and 31b. Therefore, when the two rollers 31a and 31b rotate, the belt 31c rotates. The support portion 32 is a member that supports the tire 1 rotatably around the rotation axis La. The tire 1 is supported by the support portion 32 while being mounted on the upper surface of the belt 31c. The speed of the motor for rotating the two rollers 31a and 31b is controlled by the control device 40. Therefore, the tire 1 rolls on the belt 31c at a predetermined speed with the rotation of the belt 31c at the predetermined speed.

  The types of the microphones 20 and 21 are not particularly limited, and commercially available microphones can be used. In the present embodiment, as described above, the microphones 20 and 21 are respectively attached to both edges of the shoulder portion 6, the quarter portion 7, and the center portion 8 at the front Fr in the rolling direction of the tire 1 shown in FIG. It is installed in the corresponding position. However, the microphones 20 and 21 need not be provided for all of the shoulder section 6, the quarter section 7, and the center section 8, that is, at least one of the shoulder section 6, the quarter section 7, and the center section 8. Can be installed. In the tire height direction, the microphones 20 and 21 (not shown in FIG. 4) are installed in a range from the surface of the road surface portion 31 on which the tire 1 is mounted to the tire rotation axis La in FIG.

  Referring to FIG. 6, control device 40 includes hardware including a storage device such as a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory), and software mounted thereon. It is built by The control device 40 includes a first energy calculation unit 41, a second energy calculation unit 42, a measurement ratio calculation unit 43, a storage unit 44, a determination unit 45, and a speed control unit 46.

  The first energy calculator 41 calculates an energy value (first measured energy value) E1 in a predetermined frequency range from the sound pressure of the pattern noise measured by the microphone (first sound pressure sensor) 20. Further, the second energy calculation unit 42 calculates an energy value (second measured energy value) E2 in a predetermined frequency range from the sound pressure of the pattern noise measured by the microphone (second sound pressure sensor) 21. The first measured energy value E1 and the second measured energy value E2 are energy values calculated from the sound pressure when the tire 1 rolls.

  The predetermined frequency range is calculated as Δf by the following equation. Here, V in the following equation is a vehicle speed V (km / h) corresponding to the rolling speed of the tire 1. Dmax indicates the maximum pitch length among the above-described block pitches, and Dmin indicates the minimum pitch length. When calculating the lower limit value f1 and the upper limit value f2 of the frequency range Δf, the speed is converted to the speed per second (m / s) by multiplying the speed per hour V (km / h) by 1000/3600. The lower limit value f1 of the frequency range Δf is obtained by dividing a value obtained by converting an hourly speed V (km / h) into a second speed by a value 1.05 times the maximum pitch length Dmax. Similarly, the upper limit value f2 of the frequency range Δf is obtained by dividing a value obtained by converting the speed per hour V (km / h) to a speed per second by a value 0.95 times the minimum pitch length Dmin. The reason why the maximum pitch length Dmax is multiplied by 1.05 and the minimum pitch length Dmin is multiplied by 0.95 is to provide a margin in a frequency range for calculating an energy value.

  A method of calculating the frequency range Δf using the above equation will be exemplified using specific numerical values. In the present embodiment, a tire 1 having a radius of 300 mm in which 34 blocks 13 are provided per circumference of the tire 1 is used. The minimum pitch length Dmin is 42 mm, the maximum pitch length Dmax is 69 mm, and the basic block pitch is 55 mm. That is, a variation of about 25% is set with respect to the basic block pitch. Further, the predetermined speed V is set to 50 km / h. When these are substituted into the above equation, the lower limit f1 is 191 Hz and the upper limit f2 is 352 Hz. Therefore, the frequency range Δf is 191 to 352 Hz.

  The energy value in the frequency range Δf is calculated as E by the following equation. Here, Pi in the following equation indicates a sound pressure at a certain frequency fi. The frequency fi is a value within the frequency range Δf (f1 ≦ fi ≦ f2). For example, in the case of the frequency range Δf (191 to 352 Hz) shown as the above numerical example, the frequency fi may be set to 191 to 352 Hz every 1 Hz. Thus, the first energy calculator 41 calculates the first measured energy value E1 in the predetermined frequency range Δf, and the second energy calculator 42 calculates the second measured energy value E2 in the predetermined frequency range Δf. .

  The measurement ratio calculation unit 43 calculates a measurement ratio Rm (E2 / E1) which is a ratio of the second measured energy value E2 to the first measured energy value E1.

  The storage unit 44 stores the reference ratio Rc as data when the tire 1 is new. In addition, a new article means a thing which is not used or is not worn. The reference ratio Rc is obtained as follows. First, a first reference energy value Ec1, which is an energy value in a predetermined frequency range Δf of the sound pressure measured by the microphone 20 when the tire 1 is new, is obtained. At the same time, when the tire 1 is new, a second reference energy value Ec2 which is an energy value of the sound pressure measured by the microphone 21 in a predetermined frequency range Δf is obtained. The reference ratio Rc is obtained as a ratio of the second reference energy value Ec2 to the first reference energy value Ec1 (Rc = Ec2 / Ec1).

  The determination unit 45 determines that the feather edge wear has occurred in the portions 6 to 8 when the measured ratio Rm differs from the reference ratio Rc by a predetermined amount or more, and otherwise determines that the feather edge wear has not occurred. judge. In the present embodiment, if the measured ratio Rm is less than or equal to half or more than twice the reference ratio Rc, it is determined that feather edge wear has occurred in the portions 6 to 8. In the present embodiment, since the microphones 20 and 21 are installed at positions corresponding to the respective parts 6 to 8, it can be determined whether or not the respective parts 6 to 8 have feather edge wear. In particular, in only one of the shoulder part 6, the quarter part 7, and the center part 8, the measurement ratio Rm is different from the reference ratio Rc by the predetermined value or more, and the measurement is performed with respect to the reference ratio Rc in the remaining two. If the ratio Rm does not differ by the predetermined amount or more, it is determined that only the portion where the measurement ratio Rm differs from the reference ratio Rc by the predetermined amount or more is unevenly worn.

  The result of the determination by the determination unit 45 is displayed on the monitor 50 as needed. In particular, a warning may be displayed on the monitor 50 when the determination unit 45 determines that it is worn.

  In the present embodiment, in order to determine the presence or absence of feather edge wear in more detail, the concept of “order” according to the tread pattern is introduced. Specifically, the above-described block pitch is set as a primary pitch. Then, according to the divided shape of the block 13 in the tire circumferential direction TR, the second, third, fourth, and higher orders are set. At each pitch of the order, the frequency range Δf is calculated, the measurement ratio Rm in the frequency range Δf for each order is detected, and compared with the reference ratio Rc for each order. If different, it is determined that feather edge wear has occurred.

  More specifically, referring to FIG. 2, if the above-described block pitch (primary pitch length) is D1, a secondary pitch length D2 that is about half the primary pitch length D1, and a quarter of D1 A fourth-order pitch length D4 of about 1 is provided. Higher-order pitch lengths such as the second-order pitch length D2 and the fourth-order pitch length D4 are provided based on how many blocks 13 are divided by the lateral grooves 14 and 15 such as sipes and narrow grooves. Therefore, in the present embodiment, the frequency range Δf is similarly calculated not only for the first order, but also for the second and fourth orders, the measurement ratio Rm is calculated, and the wear determination is performed by comparing the measured ratio Rm with the reference ratio Rc for a new product. The second and subsequent frequency ranges Δf can be obtained by multiplying the first frequency range Δf by the order. That is, in the above numerical example, the first-order frequency range Δf is 191 to 352 Hz, and the second-order frequency range Δf is 382 to 704 Hz, which is twice as large as that, and the fourth-order frequency range Δf is four times that of 764 to 1408 Hz. Becomes

  FIG. 7 is a graph showing an example of the measured pattern noise. The horizontal axis of the graph indicates the frequency [Hz], and the vertical axis indicates the sound pressure level [dB]. The frequency of the pattern noise corresponding to the primary pitch length D1 is approximately 250 Hz, the frequency of the pattern noise corresponding to the secondary pitch length D2 is approximately 500 Hz, and the frequency of the pattern noise corresponding to the quaternary pitch length D4 is approximately 500 Hz. It is 1000 Hz, and the peak value of the sound pressure level can be confirmed at these frequencies. More specifically, the sound pressure level does not increase only at each point of these frequencies, but increases at a certain width near these frequencies. This is because the pitch lengths D1, D2, and D4 of the respective orders are set with variations. Therefore, when performing a wear determination, it is effective to perform energy comparison in a frequency range near the peak value, instead of comparing sound pressure at a frequency at a peak value. Therefore, in the present embodiment, energy comparison is performed in the frequency range Δf near the peak value of each order to determine the presence or absence of feather edge wear.

  The speed controller 46 of the present embodiment controls a motor that rotates the two rollers 31a and 31b. Therefore, the speed at which the tire 1 rolls can be controlled by the speed control unit 46, and the frequency range Δf can be adjusted. Preferably, the speed V is controlled such that the frequency range Δf is out of the columnar resonance frequency range Δg of the longitudinal grooves 11a to 11d of the tire 1. The air column resonance frequency range Δg is obtained by the following equation. Here, c is the speed of sound, and L is the length of the vertical grooves 11a to 11d. α is a correction coefficient and takes a value of 0.6 or more and 0.8 or less.

  A method of calculating the frequency range Δf using the above equation will be exemplified using specific numerical values. If the pipe length L of the vertical groove 11d is 120 mm and the sound speed c is 340 (m / s), the columnar resonance frequency range Δg takes a value of 850 to 1133 Hz. Therefore, it is preferable that the speed control unit 46 sets the speed V so as to set the frequency range Δf while avoiding the range Δg obtained as described above.

  However, it may be difficult to deviate the frequency range Δf of all orders from the columnar tube resonance frequency range Δg. Also in the numerical example of the present embodiment, the fourth-order frequency range Δf (764 to 1408 Hz) partially overlaps with the air column resonance frequency range Δg (850 to 1133 Hz). As described above, when it is difficult to remove the entire order frequency range Δf from the columnar tube resonance frequency range Δg, the most prominent order frequency range Δf may be removed from the columnar tube resonance frequency range Δg. For example, in the example of the present embodiment in FIG. 7, since the sound pressure level of the fourth-order pattern noise (around 1000 Hz) is most conspicuous, the speed V is changed to change only the fourth-order frequency range Δf to the columnar resonance frequency. It may be out of the range Δg. In addition to this, the speed V may be changed so that the frequency range Δf of the second most prominent order may be excluded from the columnar tube resonance frequency range Δg.

  According to the method and the apparatus for determining the feather edge wear of the pneumatic tire of the present embodiment, the following advantages are provided.

  In the present embodiment, the sound pressure of the pattern noise is measured using the microphones 20 and 21 installed at positions corresponding to both edges of the portions 6 to 8 in the tire width direction TW. Therefore, it is possible to measure the sound pressure of the pattern noise generated by each of both edges of the portions 6 to 8 in the tire width direction TW. By comparing the ratio (measurement ratio Rm) of the first and second measured energy values E1 and E2 calculated in the predetermined frequency range Δf of these sound pressures with that at the time of brand-new (reference ratio Rc), The difference in wear can be detected. Therefore, whether or not feather edge wear has occurred can be determined based on the difference in the wear.

  Further, in the present embodiment, the predetermined frequency range Δf is specifically defined. In particular, the shoulder portion 6, the quarter portion 7, and the center portion 8 extending in the tire circumferential direction TR are formed with horizontal grooves extending in the tire width direction TW, so that a block having a predetermined pitch length may be formed. is there. The block 13 of the shoulder portion 6 illustrated in the present embodiment comes into contact with the ground at regular time intervals with the rotation of the tire 1 to generate pattern noise. Therefore, by adjusting the predetermined frequency range Δf for calculating the energy to the frequency of occurrence of the pattern noise, it is possible to accurately detect the feather edge wear. However, the block pitch is designed to have a certain degree of variation (Dmin to Dmax) in order to prevent pattern noise from concentrating on a specific frequency. It should be noted here that the block pitch is designed to have a certain degree of variation (Dmin to Dmax) in order to prevent pattern noise from concentrating on a specific frequency. Therefore, it is effective to calculate the energy not in one specific frequency corresponding to a specific block pitch but in a predetermined frequency range Δf corresponding to a block pitch having a variation as in the present embodiment. In the present embodiment, the block 13 of the shoulder section 6 has been described as an example. However, the quarter section 7 and the center section 8 can calculate the frequency range Δf in the same manner.

  Further, in the present embodiment, since the reference ratio Rc and the measurement ratio Rm are compared for each degree of the pattern noise, more detailed determination can be made. More specifically, when one block 13 is divided in the tire circumferential direction TR by lateral grooves 14, 15 (see FIG. 2) such as sipes or other narrow grooves, pattern noise occurs at a frequency higher than the block pitch. . In the present embodiment, the high-frequency pattern noise is referred to as second-order, third-order, fourth-order,..., And the feather edge wear is reduced by performing an energy comparison in a unit more detailed than a block in consideration of the order. We evaluate in more detail.

  Further, in the present embodiment, at the time of energy comparison, the presence or absence of occurrence of feather edge wear is determined using half or twice as a threshold value. This is because when the energy value of the pattern noise is half or doubled, there is a difference that can be felt by a general driver. In addition, since the threshold value is set to half or twice the energy value, even if the measured energy value changes slightly due to the influence of disturbances such as wind and road surface conditions, the occurrence of feather edge wear does not occur even if the measured value changes slightly. Can be accurately determined.

  Further, in the present embodiment, since the predetermined speed V is set so that the predetermined frequency range Δf is out of the columnar resonance frequency range, pattern noise is generated in the circumferential groove (vertical groove) of the tread portion 5 of the tire 1. 11a to 11d) can be prevented from being affected by air column resonance. If the evaluation is performed at a speed at which the frequency range of the pattern noise coincides with the frequency range of the columnar resonance, the groove becomes shallower with each wear, so that the influence of the columnar resonance decreases. That is, the influence of columnar resonance during the evaluation is not constant. Therefore, the pattern noise can be accurately measured by setting the predetermined speed so that the predetermined frequency range deviates from the column resonance frequency range.

  In the present embodiment, the microphones 20 and 21 are installed in the region S1 'in the front Fr of the rolling direction of the tire 1 to measure the pattern noise (see FIG. 3). Since the pattern noise appears clearly and strongly in front of the rolling direction Fr of the tire 1, the sound pressure of the pattern noise can be efficiently measured by this installation position.

  As described above, the specific embodiments of the present invention have been described. However, the present invention is not limited to the above embodiments, and can be implemented with various modifications within the scope of the present invention.

  For example, the road surface portion 31 of the rolling device 30 may not be flat. Specifically, as shown in FIG. 8, the road surface portion 31 may include a rotatable drum 31 d having a sufficiently large radius of curvature as compared with the tire 1.

  Alternatively, rolling device 30 may be a real vehicle.

1 Pneumatic tires (tires)
2 Wheel rim 5 Tread part 6 Shoulder part 7 Quarter part 8 Center part 11a, 11b, 11c, 11d Vertical groove 12 Horizontal groove 13 Block 14, 15 Horizontal groove 20 Microphone (first sound pressure sensor)
21 microphone (second sound pressure sensor)
30 Rolling device (automobile)
31 road surface section 31a, 31b roller 31c belt 31d drum 32 support section 40 control device 41 first energy calculation section 42 second energy calculation section 43 measurement ratio calculation section 44 storage section 45 determination section 46 speed control section 50 monitor

Claims (8)

Prepare a pneumatic tire having a portion extending in the tire circumferential direction divided by at least one circumferential groove,
A first sound pressure sensor and a second sound pressure sensor are respectively installed at positions corresponding to both edges of the region in the tire width direction,
Measuring the sound pressure of the pattern noise generated by the first sound pressure sensor and the second sound pressure sensor by rolling the new pneumatic tire at a predetermined speed,
Calculating a first reference energy value, which is an energy value in a predetermined frequency range of a sound pressure of the pneumatic tire when new, measured by the first sound pressure sensor;
Calculating a second reference energy value, which is an energy value of the sound pressure of the pneumatic tire at the time of brand new in the predetermined frequency range measured by the second sound pressure sensor,
Calculating a reference ratio that is a ratio of the second reference energy value to the first reference energy value;
Rolling the pneumatic tire at the predetermined speed, measuring the sound pressure of the pattern noise generated by the portion by the first sound pressure sensor and the second sound pressure sensor,
Calculating a first measured energy value that is an energy value of the sound pressure of the pneumatic tire measured by the first sound pressure sensor in the predetermined frequency range;
Calculating a second measured energy value that is an energy value of the sound pressure of the pneumatic tire measured by the second sound pressure sensor in the predetermined frequency range;
Calculating a measurement ratio that is a ratio of the second measured energy value to the first measured energy value;
A method for determining feather edge wear of a pneumatic tire, comprising: determining that feather edge wear has occurred at the site when the measured ratio differs from the reference ratio by a predetermined value or more. The predetermined frequency range, using the vehicle speed V corresponding to the predetermined speed, the minimum pitch length Dmin and the maximum pitch length Dmax of the block pitch in the tire circumferential direction of the tread pattern of the pneumatic tire, The method for judging feather edge wear of a pneumatic tire according to claim 1, wherein the method is calculated as Δf by the following equation.

Assuming that the block pitch is a primary pitch, the predetermined frequency range is calculated at a pitch of each order according to the divided shape of the block in the tire circumferential direction,
Calculate the reference ratio and the measurement ratio in the predetermined frequency range for each order,
3. The feather edge wear is determined to occur in the region when the measured ratio differs from the measured ratio by a predetermined amount or more by comparing the reference ratio and the measured ratio for each order. For determining the feather edge wear of pneumatic tires.   The pneumatic tire according to any one of claims 1 to 3, wherein it is determined that feather edge wear has occurred in the portion when the measured ratio is equal to or less than half or equal to or greater than twice the reference ratio. Method for determining feather edge wear.   The method for determining feather edge wear of a pneumatic tire according to any one of claims 1 to 4, wherein the predetermined speed is a speed at which the predetermined frequency range deviates from an air column resonance frequency range.   The feather edge wear of the pneumatic tire according to any one of claims 1 to 5, wherein the first sound pressure sensor and the second sound pressure sensor are installed in the rolling direction front of the pneumatic tire. Judgment method.   The method for determining feather edge wear of a pneumatic tire according to any one of claims 1 to 6, wherein the portion is a shoulder portion, a quarter portion, or a center portion. A rolling device for rolling at a predetermined speed a pneumatic tire having a portion extending in the tire circumferential direction divided by at least one circumferential groove;
A first sound pressure sensor and a second sound pressure sensor that are installed at positions corresponding to both edges in the tire width direction of the portion and measure the sound pressure of pattern noise generated when both edges of the portion touch the ground; When,
When the pneumatic tire is new, measured by the second sound pressure sensor with respect to a first reference energy value, which is an energy value in a predetermined frequency range of the sound pressure measured by the first sound pressure sensor when the pneumatic tire is new. A storage unit that stores a reference ratio that is a ratio of a second reference energy value that is an energy value of the determined sound pressure in the predetermined frequency range;
A first energy calculator that detects a first measured energy value that is an energy value of the sound pressure measured by the first sound pressure sensor in the predetermined frequency range;
A second energy calculator that detects a second measured energy value that is an energy value of the sound pressure measured by the second sound pressure sensor in the predetermined frequency range;
A measurement ratio calculation unit that calculates a measurement ratio that is a ratio of the second measured energy value to the first measured energy value;
A determination unit that determines that feather edge wear has occurred in the portion when the measured ratio differs from the reference ratio by a predetermined amount or more, the feather edge wear determination device for a pneumatic tire.

Images