JP6218298B2 - Tire and tire characteristic evaluation method - Google Patents

Description

  The present invention relates to a tire and a tire characteristic evaluation method.

  Patent Document 1 discloses a tire performance prediction method. In such a method, the apparatus shown in Patent Document 2 and the measurement technique shown in Non-Patent Document 1 are used. In this method, the loss tangent of the rubber composition serving as a reference is measured based on sound waves. The sound wave has a frequency of 0.01 MHz to 100 MHz.

  The method further measures the maximum friction coefficient of such a rubber composition. The correlation between the loss tangent and the maximum friction coefficient is specified from these measured values. Also measure the loss tangent of the sample. The maximum coefficient of friction of the sample is predicted based on the correlation and the loss tangent of the sample.

JP 2010-085340 A JP 2007-047130 A International Publication No. 2009/014234 JP 2010-59411 A JP 2014-80613 A

Tetsuya Kunizawa, Qing-Qing Ni, "HIGH FREQUENCY VISCOELASTIC PROPERTIES OF NANO PARTICLES-FILLED RUBBER COMPOUNDS BY ULTARSONIC MEASUREMENT", [online], 2007, ICCM-16 Local Organizing Committee, [June 18, 2015], internet <URL ： http : //www.iccm-central.org/Proceedings/ICCM16proceedings/contents/pdf/ThuA/ThAA1-05ge_kunizawat224577p.pdf> Japan Electromechanical Industry Association, Ultrasonic Engineering, p135-137 Satoshi Yuzaki, Takuo Sone, Tetsuo Tominaga, Munetaka Iwano, “Improvement of Silica Dispersibility and Reduction of Rolling Resistance by Terminal Modified S-SBR”, JSR TECHNICAL REVIEW, 2010, No.117, p.16-21 C. Wrana, U. Eisele und S. Kelbch, "Measurement and Molecular Modeling of Rolling Resistance in Tire Treads", [online], KGK Kautschuk Gummi Kunststoffe 53. Jahrgang, Nr.3 / 2000, p.126-128 Ryosuke Matsuzaki, "Development of Smart Tires without Sensor-less Wireless Strain Measurement", [online], KAKEN Database of Grants-in-Aid for Scientific Research, Internet <URL: https://kaken.nii.ac.jp/d /p/06J05708.en.html> Masaaki Kageyama, "Sensor technology that uses tires to the end, developed by Bridgestone (2/4)", [online], November 14, 2014, MONOist, Internet <URL: http: //monoist.atmarkit .co.jp / mn / articles / 1411/14 / news153_2.html>

  By using the above method, tires with high grip performance can be selected from various tires. However, the above method is not suitable for selecting a tire having a low rolling resistance from a tire having a high grip performance. It is difficult to select tires having high grip performance and low rolling resistance from various tires using the above method.

  The present invention provides a tire and a tire characteristic evaluation method. Such tires exhibit high grip performance and small rolling resistance. The tire has a high wet grip performance. This method is intended to provide a method for evaluating whether or not a tire to be tested exhibits high grip performance and small rolling resistance. It is evaluated whether the tire exhibits high wet grip performance and small rolling resistance.

[Tire] In the tire according to the present invention, the Pain effect is applied to the optimization of wet grip and rolling resistance. The Payne effect represents the strain dependence of the storage modulus. The Payne effect also represents a strain-dependent frequency shift of the loss tangent. The Payne effect has been applied to the evaluation of filler dispersion. In the tire of the present invention, a rubber compound having a large distortion-dependent frequency shift of loss tangent is arranged on the tread. Due to this feature, the tire wet grip and rolling resistance are optimized.

[1] A first aspect of the present invention is a tire having a tread exhibiting a predetermined loss tangent. In the first aspect, when the loss tangent exhibited by a test piece having the same composition as that of the rubber constituting the tread is measured by vibrating the test piece as the predetermined loss tangent, the loss tangent is calculated. Varies depending on the magnitude and frequency of strain in the vibration of the specimen.

  In the first aspect, the first loss tangent is the loss tangent exhibited by the test piece when the test piece vibrates at a first frequency with a first strain. The first strain is either a shear strain or a tensile strain.

  In the first aspect, the shear strain is the amplitude in the tangential direction with respect to the thickness in the normal direction of the surface when the test piece vibrates with shear deformation in the tangential direction of the surface of the test piece. It is expressed by the ratio of The tensile strain is expressed as a ratio of the amplitude in the normal direction to the thickness in the normal direction when the test piece vibrates with tensile deformation in the normal direction.

  In the first aspect, the second loss tangent is the loss tangent exhibited by the test piece when the test piece vibrates so as to include the second frequency component with the second strain. The second strain is obtained when the elastic stress wave is generated in the test piece by radiating an ultrasonic pulse wave to the test piece, and the elastic stress is equal to the duration of the pulse wave. It represents the ratio of the amplitude of the elastic stress wave to the distance traveled by the wave.

  In the first aspect, the second frequency is higher than the first frequency. The second loss tangent is 60 times or more the first loss tangent. The second strain may be greater than the first strain.

[2] The first loss tangent is preferably 0.2 or less. The second loss tangent is preferably 0.5 or more.

[3] The first strain is preferably 10% or less. The second strain is preferably 1% or more and 1 × 10 ² % or less. The first frequency is preferably 1 Hz or more and 1 × 10 ² Hz or less. The second frequency is preferably included in a range of 0.1 MHz to 1 × 10 ² MHz.

[4] The elastic stress wave is preferably either a longitudinal wave or a transverse wave.

[5] A second aspect of the present invention is a tire having a tread exhibiting a predetermined loss tangent. Similar to the first aspect, in the second aspect, the first loss tangent is expressed as a loss tangent exhibited by the tread when the tread vibrates at a first frequency with a first strain.

  Similar to the first aspect, in the second aspect, the first strain is either a shear strain or a tensile strain. The shear strain is expressed as a ratio of the amplitude in the tangential direction to the thickness in the normal direction of the surface when the tread vibrates with shear deformation in the tangential direction of the surface of the tread. The tensile strain is expressed as a ratio of the amplitude in the normal direction to the thickness in the normal direction when the tread vibrates with tensile deformation in the normal direction.

  Unlike the first aspect, in the second aspect, the second loss tangent is expressed as the loss tangent exhibited by the tread when the tread vibrates to include a second frequency component with a second strain. Is done. In the second strain, when an elastic stress wave is generated in the tread by radiating an ultrasonic pulse wave to the tread, the elastic stress wave has the same length as the duration of the pulse wave. The ratio of the amplitude of the elastic stress wave to the traveling distance is represented.

  Similar to the first aspect, in the second aspect, the second frequency is higher than the first frequency. The second loss tangent is 60 times or more the first loss tangent. The second loss tangent may be greater than the first strain.

[Traffic control system]
[6] A third aspect of the present invention is a traffic control system. The traffic control system includes a control device provided in a vehicle including the tire, a sensor built in the tire, and a server provided outside the vehicle. In a third aspect, the control device controls traveling of the vehicle.

The sensor measures strain of the tire and transmits data obtained based on the measurement to the control device. The control device receives the data and transmits the data to the server. The server receives the data, refers to information on the rolling resistance and grip of the tire with respect to the strain included in the data, and makes a travel plan for the vehicle based on the reference.

[Characteristic Evaluation Method] In the tire characteristic evaluation method according to the present invention, a rubber compound or a tread having a large loss-tangent strain-dependent frequency shift is selected. Therefore, the method of the present invention is suitable for providing a tire in which the wet grip and rolling resistance of the tire are optimized.

[7] A fourth aspect of the present invention is a method for evaluating characteristics of a tire by measuring a loss tangent exhibited by a tread of the tire. In a fourth aspect, as the loss tangent, a loss tangent exhibited by the test piece is obtained by vibrating a test piece having the same composition as the rubber composition of the tread at a predetermined strain magnitude and a predetermined frequency. Measure.

  In a 4th aspect, the 1st loss tangent which the said test piece exhibits is acquired by vibrating the said test piece with a 1st frequency with a 1st distortion. The first strain is a shear strain or a tensile strain. The shear strain represents the ratio of the amplitude in the tangential direction to the thickness in the normal direction of the surface when the test piece vibrates with shear deformation in the tangential direction of the surface of the test piece. . The tensile strain is expressed as a ratio of the amplitude in the normal direction to the thickness in the normal direction when the test piece vibrates with tensile deformation in the normal direction.

  In the fourth aspect, the test piece is vibrated so as to include a component of the second frequency with a second strain before, after or simultaneously with the acquisition of the first loss tangent. Get the second loss tangent to be presented. In the second strain, when an elastic stress wave is generated in the test piece by radiating an ultrasonic pulse wave to the test piece, the elastic stress wave advances in the same time as the duration of the pulse wave. The ratio of the amplitude of the elastic stress wave to the distance to be measured.

  In the fourth aspect, the second frequency is higher than the first frequency. After the measurement, it is determined whether the second loss tangent is 60 times or more of the first loss tangent. The second strain may be greater than the first strain.

[8] The first strain is preferably 10% or less. The second strain is preferably 1% or more and 1 × 10 ² % or less.

[9] The first frequency is preferably 1 Hz or more and 1 × 10 ² Hz or less. The second frequency is preferably included in a range of 0.1 MHz to 1 × 10 ² MHz.

[10] The elastic stress wave is preferably either a longitudinal wave or a transverse wave.

[11] A fifth aspect of the present invention is a method for evaluating characteristics of a tire by measuring a loss tangent exhibited by a tread of the tire. Unlike the fourth aspect, in the fifth aspect, the first loss tangent exhibited by the tread is obtained as the loss tangent by vibrating the tread at a first frequency with a first strain.

  Similar to the fourth aspect, in the fifth aspect, the first strain is a shear strain or a tensile strain. The shear strain represents the ratio of the amplitude in the tangential direction to the thickness in the normal direction of the surface when the tread vibrates with shear deformation in the tangential direction of the surface of the tread. The tensile strain is expressed as a ratio of the amplitude in the normal direction to the thickness in the normal direction when the tread vibrates with tensile deformation in the normal direction.

  Unlike the fourth aspect, in the fifth aspect, simultaneously with the acquisition of the first loss tangent, the tread is vibrated so as to include the component of the second frequency with the second distortion, thereby obtaining the loss tangent. A second loss tangent exhibited by the tread is acquired. The second strain is a distance that the elastic stress wave travels in the same time as the duration of the pulse wave when an elastic stress wave is generated in the tread by emitting an ultrasonic pulse wave to the tread. Represents the ratio of the amplitude of the elastic stress wave to.

  Similar to the fourth aspect, in the fifth aspect, the second frequency is higher than the first frequency. After the measurement, it is determined whether the second loss tangent is 60 times or more of the first loss tangent. The second strain may be greater than the first strain. The second loss tangent may be acquired before or after the acquisition of the first loss tangent.

  According to the present invention, a tire exhibiting high grip performance and small rolling resistance can be provided. According to the present invention, it is possible to provide a method for evaluating whether or not a tire to be tested exhibits high grip performance and small rolling resistance.

It is a figure which shows the radiation | emission of the ultrasonic wave to a test piece. It is a graph which shows the waveform data of an ultrasonic wave. It is a schematic diagram of DMA measurement by tensile deformation. It is a schematic diagram of DMA measurement by shear deformation. It is a schematic diagram which shows the shear strain which acts on a tire. It is a block diagram which shows a measuring apparatus. It is a figure which shows an ultrasonic measurement. It is a figure which shows the vehicle equipped with the tire provided with a sensor. It is a graph showing the example of a design of a tire. It is a graph showing the relationship between the frequency and loss tangent in a design example. It is a graph showing the comparative example 1 of a tire design. It is a graph showing the comparative example 2 of a tire design. It is a schematic diagram of the apparatus which shear-deforms a test piece. It is a graph which shows the relationship between a strain vibration and a viscoelasticity measured value. FIG. 1 is a configuration diagram 1 for testing a tire. FIG. 3 is a configuration diagram 2 for testing a tire.

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

[tire]
The tire of this embodiment has a tread. The tread touches the road surface. The tread is required to have grip performance and fuel saving performance as its main functions. Grip performance depends on high frictional force. Fuel saving performance depends on low rolling resistance.

  In the present embodiment, the tire characteristics are complex characteristics. Such characteristics include the high grip performance exhibited by the tire during acceleration, deceleration and turning. Grip performance is said to depend on adhesion friction and hysteresis friction. Of the high grip performance, particularly high wet grip performance is important. Adhesion friction is inhibited by the surface of the tread getting wet with water. At this time, the contribution of the dry grip performance decreases, and the tire becomes slippery with respect to the road surface. Therefore, wet grip performance is important for maintaining safety. Wet grip performance is affected by hysteresis friction. Hysteresis friction relies on energy loss due to vibrations that occur with the sliding of the tread surface against the road surface. For this reason, even if the surface of a tread gets wet with water, hysteresis friction is hard to be inhibited.

  The composite characteristics include the low rolling resistance exhibited by the tire at other times. Other times include the case where the tire rolls linearly at a constant speed. It is said that the rolling resistance frequency depends on the tire rotation speed. It is said that both wet grip performance and rolling resistance have a correlation with loss tangent. Such loss tangent is an indicator of energy loss that varies depending on strain and frequency in tread vibration.

[Evaluation of tire characteristics]
In this embodiment, the evaluation of the tire characteristics is performed based on viscoelasticity measurement. Unless otherwise stated, in this specification viscoelasticity measurement means measuring loss tangent. Tan δ representing the loss tangent is obtained from the following equation.

tan δ = E ″ / E ′
The loss elastic modulus is E ″. The storage elastic modulus is E ′.

  Loss modulus and storage modulus are determined by DMA. DMA is an abbreviation for dynamic mechanical analysis. In addition to DMA, analysis using a rheometer can be used. Unless otherwise stated, in this specification, measurement of loss tangent includes obtaining loss tangent from a value measured by analysis using DMA or rheometer.

  When measuring viscoelasticity by DMA, the test object is vibrated. In this specification, the ratio between the vibration amplitude Δl and the deformation length l is referred to as “strain”. The deformation length will be described later. In the prior art documents, “strain” may be expressed as “strain amplitude”.

  It is meaningful to distinguish between viscoelasticity measurement using ultrasonic waves and viscoelasticity measurement without using ultrasonic waves. In the present specification, the former will be referred to as ultrasonic measurement for the sake of convenience unless otherwise specified. The latter is called DMA measurement for convenience. Ultrasonic measurement enables viscoelasticity measurement at a high frequency, which is not possible with DMA measurement.

  A test piece can be selected as a test object. The test piece has the same composition as that of the rubber constituting the tread. The test piece is preferably the same as the raw material of the tire tread. The rubber constituting the tread is vulcanized. The viscoelasticity is measured by vibrating the test piece. The loss tangent varies depending on the magnitude and frequency of strain in the specimen vibration.

  FIG. 1 is a diagram illustrating an example in which ultrasonic waves are incident on a test piece as an example of viscoelasticity measurement. The loss tangent of the test piece 43 can be measured by radiating sound waves to the entire test piece 43. The incident sound wave 47 is radiated from the oscillator 50 toward the test piece 43.

  The incident sound wave 47 shown in FIG. 1 propagates through the test piece 43 as an elastic stress wave. The test piece 43 is in contact with the oscillator 50. Therefore, the amplitude of the elastic stress wave is the same as that of the oscillator 50. The elastic stress wave may be a longitudinal wave or a transverse wave.

  In this embodiment, the viscoelasticity of the test piece can also be measured by the method shown in FIG. It is presumed that a tread having the same composition as the rubber constituting the test piece has the same viscoelasticity as the test piece. Therefore, the viscoelasticity of the tire can be measured in a pseudo manner by the above measurement.

[Strain and frequency applied to vibration]
<Overview>
The tire of the present embodiment is a tire having a tread that exhibits a predetermined loss tangent. Such loss tangent varies depending on the strain and frequency in the tread vibration. When evaluating the characteristics of a tire, vibrations characterized by such strain and frequency are applied to the tire. Such vibration will be described for each ultrasonic measurement and DMA measurement. Moreover, the vibration provided to the tire that actually rotates on the road surface will be described. After describing these vibrations, these vibrations will be compared.

<Ultrasonic measurement>
The ultrasonic wave used in ultrasonic measurement is a pulse wave. As shown in FIG. 1, the pulse wave enters the test piece 43 from the oscillator 50 as an incident sound wave 47. The incident sound wave 47 generates an elastic stress wave in the test piece 43. In other words, the incident sound wave 47 behaves as an elastic stress wave in the test piece 43.

  FIG. 2 shows an example of waveform data of a pulse wave. The waveform data is represented by the measurement result of the time change of the vibration of the pulse wave. The pulse wave is emitted to the test piece. The pulse wave has a predetermined duration. A vertical axis | shaft shows the amplitude of the pulse wave in the test piece 43 shown in FIG. The unit is μm. The horizontal axis indicates time. The unit is microseconds (μs).

  The pulse wave duration λt is calculated from FIG. The unit of λt is microseconds (μs). The duration of the pulse wave is the time between the start time 46 of the pulse wave and the end time 48 of the pulse wave. The start time 46 is the appearance time of the beginning of the pulse wave. The start time 46 is 0.56 (μs). The end time 48 is the appearance time of the end of the pulse wave. The end time 48 of the pulse wave is 0.84 (μs). λt is calculated according to the following formula.

λt = 0.84 (μs) −0.56 (μs) = 0.28 (μs)
In the pulse wave, waves in a wide frequency band are superimposed. For this reason, it is common to define the range where the strain extends by the above definition. In addition, when compared with a case where a wave close to a single wavelength as described later is used, a wavelength of one cycle, which is a normal wavelength, may be used to represent a range in which distortion is reached.

  Table 1 below shows each value related to the strain of the test piece during ultrasonic propagation. The strain of the test piece is a strain in the test piece generated according to the pulse waveform by the elastic stress wave.

  Measurement ultrasonic waves are ultrasonic waves received with higher sensitivity than powerful ultrasonic waves. Waveform data of measurement ultrasonic waves is shown in FIG. The reception of ultrasonic waves is performed by, for example, polycrystal of PZT (lead zirconate titanate). High-power ultrasound refers to ultrasound having a larger amplitude than measurement ultrasound.

  V represents a general value of sound velocity in rubber. An example of rubber is vulcanized SBR (styrene butadiene rubber). The source is Non-Patent Document 2. The test piece 43 shown in FIG. 1 may be rubber.

  The amplitude S represents a general amplitude value of PZT generally used in the oscillator 50 shown in FIG. The general amplitude of PZT is the maximum value of the change amount when the thickness of the oscillator 50 changes periodically. When a spike voltage or a step voltage is applied to the polycrystal of PZT, the thickness changes periodically. Such a change is due to the inverse piezoelectric effect. As a result, an ultrasonic wave having an amplitude S can be transmitted. As shown in Table 1, the amplitude S of the powerful ultrasonic wave is 150 times the amplitude S of the ultrasonic wave for measurement. In high-power ultrasonic waves, the frequency dispersion tends to be narrow and the wave number tends to increase. However, in the calculation of the strain, it is only necessary to calculate the range where the strain reaches at the wavelength of one cycle, which is a normal wavelength, as in the case of the pulse wave.

  Since the oscillator 50 shown in FIG. 1 is in contact with the test piece 43, the incident sound wave 47 is not substantially impaired. Therefore, the test piece 43 vibrates with the same amplitude as that of the oscillator 50. That is, the amplitude of the elastic stress wave in the test piece 43 is S.

  Let λl be the distance length of one waveform of the pulse wave. λl is the travel distance when the elastic stress wave travels through the test piece 43 at the speed of sound V for the same length of time as the duration λt. λl is obtained from the sound speed V and the duration λt. The strain generated in the test piece 43 shown in FIG. The strain ε is expressed by the following formula.

  ε = S / λl

  The above equation can be derived as follows. As described above, the strain is the ratio between the vibration amplitude Δl and the deformation length l. Therefore, it is expressed as ε = Δl / l. The amplitude Δl is the amplitude S described above. l is considered to be the range where the specimen is deformed by the influence of the pulse wave. Therefore, l can be the distance length λl of the waveform. It can be said that ε = S / λl. The strain ε is the second strain according to this embodiment.

  The test piece 43 shown in FIG. 1 vibrates in a predetermined band so as to include a vibration component of the second frequency with a second strain. Such vibrations appear as a result of the propagation of the pulse wave. The frequency f shown in Table 1 is the reciprocal of λt. The frequency f is a second frequency. The second frequency is the frequency.

  As shown in FIG. 2, the pulse wave includes vibration components in a wide range of frequencies in one waveform. The frequency of the vibration component included in the pulse wave is dispersed within a predetermined band range. Such a vibration may be a combined vibration composed of a plurality of simple vibrations having a frequency included in the band. Here, the simple vibration may be a continuous wave having a single frequency and having a duration of λt. When generating strong ultrasonic waves using resonance, the frequency dispersion level may be small. Therefore, the vibration component included in the pulse wave may exhibit dispersion that is small enough that the pulse wave itself can be regarded as a single vibration having a duration of λt.

  The second loss tangent according to the present embodiment is a loss tangent exhibited by the test piece 43.

[DMA measurement]
<Tensile strain>
FIG. 3 is a schematic diagram of DMA measurement by tensile strain. Tensile strain is an example of the first strain. The tensile strain occurs when the test piece 43 vibrates with tensile deformation. The test piece 43 vibrates with tensile deformation in the normal direction of the surface 42 of the test piece 43. At this time, the tensile strain is expressed by the ratio of the amplitude Δl in the normal direction to the test piece length l. The test piece length l is the length of the test piece 43 in the longitudinal direction in the figure. The unit is meters (m).

  Table 2 shows an example in which strain is measured by such DMA measurement. Such a DMA measuring apparatus can normally perform normal measurement only up to 100 Hz due to mechanical constraints such as resonance. Even in special cases, 1000Hz is considered the limit of normal measurement. In addition, there is a restriction that only a low frequency measurement can be performed with a large strain.

  The test piece length l is the test piece length l when no stress is generated on the test piece. The test piece 43 is made of vulcanized SBR. Strain is a percentage of the ratio of amplitude Δl and specimen length l. The test piece 43 vibrates at the first frequency with the first strain. The first frequency is the frequency. In this embodiment, the loss tangent exhibited by the test piece 43 is referred to as a first loss tangent.

<Shear strain>
FIG. 4 is a schematic diagram of DMA measurement by shear strain. Shear strain is an example of the first strain. Shear strain occurs when the specimen vibrates with shear deformation. In other words, shear deformation and shear deformation. The test piece 43 vibrates with shear deformation in the tangential direction of the surface 42 of the test piece 43. At this time, the shear strain γ is expressed by the ratio of the amplitude Δs in the tangential direction to the thickness in the normal direction of the surface 42. The thickness in the normal direction is the specimen thickness t.

  Table 3 shows an example in which strain is measured by such DMA measurement. Such a DMA measuring apparatus can normally perform normal measurement only up to 100 Hz due to mechanical constraints such as resonance. Even in special cases, 1000Hz is considered the limit of normal measurement. In addition, there is a restriction that only a low frequency measurement can be performed with a large strain.

  The test piece thickness t in the table is measured when no stress is generated in the test piece 43 shown in FIG. The test piece 43 is made of vulcanized SBR. The shear strain γ is a ratio (%) between the amplitude Δs and the specimen thickness t. The test piece 43 vibrates at the first frequency with the first strain. The first frequency is the frequency. In this embodiment, the loss tangent exhibited by the test piece 43 is referred to as a first loss tangent.

[Shear strain acting on tires]
FIG. 5 is an example of shear strain acting on a tire. The tire is 100% slippery. 100% slip means a tire locked state. The tire has a tread. In such a state, the tread vibrates. The tread has a plurality of blocks. A block is a rectangular parallelepiped convex part surrounded by the groove | channel formed in the tread surface.

  FIG. 5 shows a block 53 as an example of the block. The block 53 has a block surface 54. The block 53 is connected to the entire tread at the base of the block 53. Such a base is shown as a virtual base surface 56 in the figure. The base surface 56 and the block surface 54 are located on opposite sides. When the tire stands upright and is in contact with the road surface, the plurality of block surfaces 54 are in contact with the road surface.

  The block surface 54 shown in FIG. 5 is parallel to the tangential direction of the tread surface. A shear force acts on the tread surface in a tangential direction with respect to the tread. As the shearing force is generated, shear strain is generated in the tread.

  The frictional force 55 shown in FIG. 5 is a static frictional force. Each block surface in contact with the road surface receives a frictional force 55. The frictional force 55 is a frictional force generated by hysteresis friction. Hysteresis friction is friction generated depending on the vibration frequency of the tread.

  Tire wet grip relies on hysteresis loss. It is known from the comparison between the frequency characteristic of loss tangent and the speed characteristic of the friction coefficient that such a dependency appears when the vibration frequency of the tread belongs to the megahertz band.

  Δs shown in FIG. 5 is a deformation amount. The unit is meters (m). The deformation amount Δs is the maximum value of the displacement of the block surface 54 when the block 53 is subjected to shear deformation. The displacement of the block surface 54 is a deviation from the base surface 56. The deformation amount Δs is the magnitude of the displacement generated by the frictional force 55 that reaches the maximum static frictional force. A method for obtaining the deformation amount Δs will be described later.

  T shown in FIG. 5 is a block thickness. The block thickness is the height of the block 53 measured from the block surface 54. That is, the block thickness is the thickness in the normal direction of the tread surface. The unit is meters (m).

  Table 4 shows an example of measuring the shear strain acting on the tire.

A is the total area of the block surfaces 54 in contact with the road surface. The unit is square meters (m ² ). The strain is a ratio (%) between the deformation amount Δs and the block thickness t. The tangential force F is the maximum frictional force that can be generated by the vehicle weight. The vehicle weight is the weight of the vehicle supported by the tire. The tangential force F is the total between the blocks 53 of the frictional force 55 that has reached the maximum static frictional force. The unit is Newton (N).

The block surface has a size of 100 mm in length and 100 mm in width. The mass of the vehicle supported by the tire is 2t. The block surface of one tire supports the mass W. The mass W is 500 kg. The force applied to the block surface is expressed by the following formula. g (m / s ² ) is the gravitational acceleration.

  W × g = 500 × 9.8 = 4900 (N)

  The coefficient of friction is 1.5. The tangential force F is obtained from the product of the force applied to the block surface and the friction coefficient. The value of the tangential force F is 7350 (N) as shown in Table 1. The shear modulus G is expressed by the following formula.

  G = (F / A) / (Δs / t)

  Based on the above formula, Δs is derived as follows.

  Δs = (F / A) / (G / t)

  As described above, the shear strain γ is the ratio between the vibration amplitude Δs and the block thickness t. Therefore, the shear strain γ can be expressed by γ = Δs / t. Such shear strain γ is related to hysteresis friction. The shear strain γ is expressed as shown in Table 4.

  In summary, the shear strain γ acting on the tire is the tread with respect to the thickness t in the normal direction of the tread surface when the tread undergoes shear deformation in the tangential direction of the tread surface due to friction when the tire is locked. Represents the ratio of the amount of deformation Δs in the tangential direction of the surface. Here, the thickness t particularly indicates the thickness of the block of the tread.

  The shear strain γ acting on the tire when the tire is not locked can be expressed in the same manner as the shear strain γ acting on the tire when the tire is locked. For example, in FIG. 5, it is assumed that the tire does not slide 100%. At this time, the frictional force 55 is a tangential force F having a predetermined magnitude although it does not reach the maximum static frictional force. Particularly in steady running, the main factor of the tangential force F is air resistance. For this reason, the shear strain γ when the tire is not locked is smaller than the shear strain γ when the tire is locked.

  The shear strain has been described above with reference to FIG. The strain acting on the tire during non-tire locking can be replaced with the tensile strain acting on the test piece. That is, even if the loss tangent of the test piece is measured using a tensile strain that does not match the direction different from the direction of the stress acting on the actual tire, the value of the loss tangent corresponding to the magnitude of the predetermined strain can be derived. . Previous studies have shown that hysteresis friction can be studied even with tensile strain. Therefore, in the DMA measurement, loss tangent corresponding to the magnitude of strain may be measured using tensile deformation. Measuring the loss tangent using tensile and compressive deformation is excellent in ease of measurement and high reproducibility.

[Evaluation conditions for tire characteristics]
The method to evaluate the characteristic which a tire concerning this embodiment has is shown. In this method, the loss tangent exhibited by the tread of the tire is measured. The measurement is performed by vibrating a test piece having the same composition as that of the rubber constituting the tread at a predetermined strain and a predetermined frequency. The measurement is preferably performed by DMA measurement and ultrasonic measurement. The characteristics of the tire are evaluated based on the results obtained by the measurement.

  The predetermined strain and the predetermined frequency imitate the distortion and frequency of vibration actually caused by the contact of the tire tread with the road surface. The strain is either the above-described shear strain or tensile strain. As described above, shear strain is generated along with shear deformation. As described above, it has been shown by conventional research that hysteresis friction can be examined even with tensile strain. The vibration applied to the tire in the viscoelasticity measurement is compared with the vibration applied to the tire that actually rotates on the road surface.

  The strain of the test piece at the time of ultrasonic measurement shown in FIG. 1 and Table 1 is larger than the strain of the test piece at the time of DMA measurement shown in FIG. 3 and Table 3. On the other hand, a strain having a magnitude equivalent to that of the tire when the tire is locked can be generated by the high-intensity ultrasonic wave. Such ultrasound can create a strain of about 35% as described above. The magnitude of the strain is close to the magnitude of the strain shown in FIG. The ultrasonic waves in the test piece are longitudinal elastic stress waves. Such elastic stress waves cause strain due to tension and compression. The correlation between the magnitude of the strain and the loss tangent mimics the correlation between the magnitude of the shear strain of the tread shown in FIG. 5 and the loss tangent exhibited by the tread.

  Vibration having a frequency equivalent to the frequency of vibration of the tire when the tire is locked can be generated by ultrasonic waves. An example of the amplitude of such an ultrasonic wave is 150 μm. An example of the frequency of such ultrasonic waves is 20 kHz to 1 MHz. The magnitude of shear strain and the frequency of vibration that can be reproduced in ultrasonic measurement are similar to the magnitude of shear strain and the frequency of vibration exhibited by the tire when the tire is locked. For this reason, the vibration of the tread when the tire is locked can be schematically reproduced by propagation and reflection of a high-frequency elastic stress wave in ultrasonic measurement. Ultrasonic measurement is suitable for high-frequency viscoelasticity measurement.

  On the other hand, in steady running, air resistance becomes the tangential force F, the main factor. Therefore, the strain is also a small value, and the frequency related to the rolling resistance is small. Thereby, the vibration of the tread when the tire is not locked can be schematically reproduced by the vibration applied to the test piece in the DMA measurement. This is because vibration is low frequency and low distortion in the DMA measurement. DMA measurement is suitable for low frequency viscoelasticity measurement.

  Based on the above, the loss tangent exhibited by the tread of the tire can be obtained by measuring the loss tangent exhibited by the test piece.

As shown in FIG. 3 or 4, the first loss tangent exhibited by the test piece is obtained by vibrating the test piece at the first frequency with the first strain. Measurement is performed by DMA measurement. The first strain is a shear strain shown in FIG. The first strain may be the tensile strain shown in FIG. The first strain is preferably 10% or less. The first frequency is preferably 1 Hz or more and 1 × 10 ² Hz or less.

  Acquisition of the second loss tangent is performed before or after acquisition of the first loss tangent. As shown in FIG. 1, the second loss tangent is obtained by vibrating the test piece in the second frequency band with the second strain. Acquisition is performed by ultrasonic measurement. The vibration is generated by an ultrasonic transducer. An example of the ultrasonic transducer is the oscillator 50.

As shown in FIG. 1, a sound wave having a second frequency band, that is, an ultrasonic wave is emitted to the test piece. Ultrasonic waves propagate through the specimen as elastic stress waves. Based on such radiation, the second loss tangent is measured. The elastic stress wave that generates the second strain may be a shear wave due to a shear strain or a longitudinal wave due to a tensile compression strain. The second strain is greater than the first strain. The second strain is preferably 1% or more and 1 × 10 ² % or less. The second frequency band is higher than the first frequency. The second frequency band is preferably included in the range of 0.1 MHz to 1 × 10 ² MHz.

  The evaluation of characteristics determines whether or not the second loss tangent is 60 times or more of the first loss tangent. If the second loss tangent is 60 times or more of the first loss tangent, it is determined that the tire having the tread exhibits high grip performance and small rolling resistance. Among various grip performances, tires are determined to be particularly excellent in wet grip performance. Such determination may be performed by a computer described later.

[Predetermined loss tangent]
Returning to the description of the tire according to the present embodiment. As described above, the tread exhibits a predetermined loss tangent. Such loss tangent varies depending on the strain and frequency in the tread vibration. Such a loss tangent exhibits values indicated as at least a first loss tangent and a second loss tangent for each different frequency.

The first loss tangent is a loss tangent exhibited by the tread when the tread vibrates at the first frequency with the first strain. The first strain is a shear strain or a tensile compression strain at the time of non-tire locking. The first frequency is a frequency of tread vibration particularly when the tire is not locked. The first strain is preferably 10% or less. The first frequency is preferably 1 Hz or more and 1 × 10 ² Hz or less.

  The first loss tangent can also be reduced with emphasis on tire deformation due to vehicle weight. An anisotropic fiber reinforced material or a material in which carbon aggregates are oriented is used as a tire material. In these materials, fibers and carbon aggregates oriented in the direction in which the tire is compressed are dominant. These materials have a higher elastic modulus in the compression direction than in other directions. For this reason, the distortion which arises in a tire is small compared with the case where other materials are used. This tendency can be seen even if the weight of the body supported by the tire increases. Tire casing design and air pressure optimization can help reduce fuel consumption. However, these are not related to friction. These are therefore considered separately from the tread design.

In the present embodiment, the second loss tangent is a loss tangent exhibited by the tread when the tread vibrates in the second frequency band with the second strain. The second strain is a shear strain particularly when the tire is locked. The second frequency band is a frequency band of tread vibration particularly when the tire is locked. The second strain is greater than the first strain. The second frequency band is higher than the first frequency. The second strain is preferably 10% or more. The second frequency band is preferably included in a range of 0.1 MHz to 1 × 10 ² MHz.

  The second loss tangent is greater than the first loss tangent. The second loss tangent is preferably 60 times or more the first loss tangent. The first loss tangent is preferably 0.2 or less, and the second loss tangent is preferably 0.5 or more. The tire having the tread exhibits high grip performance and small rolling resistance. Such tires are particularly characterized by having high fuel-saving performance along with excellent wet grip performance.

  In addition, when the loss tangent which a tread exhibits cannot be measured directly, you may change to this by measuring the loss tangent of the test piece which has the same composition as the rubber composition which comprises a tread.

[Measurement of loss tangent]
<Measurement device>
The loss tangent of the tire can be measured using a measuring apparatus 1 shown in FIG. The measuring apparatus 1 includes a control unit 10, a rheometer unit 11, an ultrasonic radiation unit 12, a signal generation unit 13, a conversion unit 14, and a processing unit 15. As the measuring device 1, a high frequency viscoelasticity measuring device manufactured by High Frequency ViscoElasticity Corporation, Yokohama, Kanagawa, Japan can be used.

  The rheometer unit 11 shown in FIG. 6 is used for low-frequency viscoelasticity measurement. The rheometer unit 11 includes a drive unit 20, a shaft 21, and a plate 22. The ultrasonic radiation unit 12 is used for high-frequency viscoelasticity measurement. The ultrasonic radiation unit 12 includes a transducer 25 and a delay material 26. The rheometer unit 11 and the ultrasonic radiation unit 12 sandwich a test piece 43. The test piece 43 is installed between the plate 22 and the delay member 26.

  The control unit 10 shown in FIG. 6 includes a circuit such as a memory and other IC (Integrated Circuit). The control unit 10 acquires a control signal from the processing unit 15. The control unit 10 applies a predetermined strain to the test piece 43 using the rheometer unit 11 based on the control signal. The control signal is distortion information. The strain information includes vibration amplitude, frequency or period, and tension information. The strain information includes strain change over time. The strain information includes information on strain period changes. The strain phase can be extracted from the strain change information.

The control unit 10 illustrated in FIG. 6 outputs a drive instruction to the drive unit 20. The drive unit 20 receives a drive instruction. The drive instruction includes vibration amplitude, frequency or period, and tension information. The frequency is 1 Hz or more and 1 × 10 ² Hz or less.

  The drive unit 20 shown in FIG. 6 vibrates the test piece 43 in the vertical direction via the shaft 21 and the plate 22 based on the drive instruction. The vertical direction is the length direction of the shaft 21. The length direction is the vertical direction in FIG. The length direction is a direction parallel to the direction from the drive unit 20 toward the plate 22. The vibration is a sinusoidal vibration. The vibration propagates from the driving unit 20 to the test piece 43 through the shaft 21 and the plate 22.

  The driving unit 20 shown in FIG. 6 pulls the test piece 43 in the length direction through the shaft 21 and the plate 22 with a force equal to the tension. The drive unit 20 includes a motor 23 and a sensor 24. Such a force is generated by the motor 23. The test piece 43 generates a stress against this force. Such stress is tension. The test piece 43 is tensile-deformed in the length direction.

  The test piece 43 shown in FIG. 6 may be torsionally deformed. The motor 23 rotates the shaft 21 in response to a drive instruction. The shaft 21 is connected to the annular plate 22. The plate 22 moves according to the movement of the shaft 21. The plate 22 is fixed to one surface of the test piece 43. Therefore, the test piece 43 receives a force from the drive unit 20. A strain corresponding to the force applied to the test piece 43 is generated, and the test piece 43 is torsionally deformed.

  The sensor 24 shown in FIG. 6 detects tension. The sensor 24 outputs the detected tension information to the conversion unit 14. The sensor 24 may detect a stress against a shearing force. The sensor 24 outputs information on the stress to the conversion unit 14.

  The information on stress includes information on time change of stress. The information on stress includes information on the periodic change of stress. The phase of the stress can be extracted from the information on the time change of the stress. The time information included in the information about the time change of the stress is the same as the time information included in the information about the time change of the strain. For this reason, the information on the time change of the stress can be compared with the information on the time change of the strain. Such stress information may be analog information or digital information.

  The conversion unit 14 may convert analog information into digital information. The conversion unit 14 outputs the converted information to the processing unit 15. The processing unit 15 receives the converted information.

  The transducer 25 shown in FIG. 6 is an oscillator. The oscillator includes a piezoelectric element. The piezoelectric element includes a piezoelectric material. A preferable piezoelectric material is PZT polycrystal. When voltage is applied to the piezoelectric material, the volume of the piezoelectric material changes. Periodic changes in voltage cause periodic changes in the volume of the piezoelectric material. A periodic change in voltage can be generated by an electrical signal received by the transducer 25. Periodic changes in the volume of the piezoelectric material produce sound waves. The measurement PZT converts a periodic change in voltage into a sound wave. The transducer 25 emits sound waves. The sound wave is the above ultrasonic wave. The ultrasonic wave is the pulse wave.

  The transducer 25 can receive in addition to transmitting sound waves. The piezoelectric material can generate a change in voltage upon receiving a sound wave. An apparatus using polycrystals of PZT can also convert sound waves into periodic changes in voltage. The transducer 25 can output a periodic change in voltage as an electrical signal.

  The transducer 25 is attached inside the ultrasonic radiation unit 12. One surface of the retarder 26 is in close contact with the transducer 25. The delay member 26 has the other surface facing one surface. The other surface is in contact with the test piece 43. The transducer 25 is connected to the direction matcher 28.

  A direction aligner 28 shown in FIG. 6 supplies an electrical signal to the transducer 25. The transducer 25 converts an electrical signal into a sound wave. The electrical signal has high frequency sound wave information. Examples of sound wave information are information that the sound wave is pulsed and information that the sound wave includes a predetermined frequency component. The transducer 25 radiates sound waves to the delay material 26. The sound wave enters the delay material 26. The delay material 26 propagates sound waves. The delay material 26 delays the sound wave.

  The delay material 26 shown in FIG. 6 radiates sound waves to the test piece 43. The sound wave enters the test piece 43. The test piece 43 reflects sound waves. The delay material 26 propagates the reflected sound wave to the transducer 25. The sound wave enters the transducer 25. The transducer 25 receives sound waves.

  The transducer 25 shown in FIG. 6 measures the magnitude of the reflected sound wave. The transducer 25 converts the reflected sound wave into an electrical signal. The transducer 25 acquires information on the magnitude of the reflected sound wave. The transducer 25 outputs an electrical signal to the direction matcher 28.

  The delay material 26 shown in FIG. 6 delays sound waves. The delay material 26 has a predetermined propagation length. As the propagation length increases, the time from when the transducer 25 radiates the sound wave to when the sound wave reflected by the test piece 43 is received becomes longer. The delay material 26 has a significant function when the transducer 25 is continuously emitting sound waves. The delay member 26 eliminates the overlap between the time that the transducer 25 emits sound waves and the time that the sound waves are incident on the transducer 25.

  The signal generator 13 shown in FIG. 6 generates an electrical signal. The signal generator 13 outputs an electrical signal. The ultrasonic radiation unit 12 receives an electrical signal. Such an electrical signal is useful for calculating the loss tangent.

  The signal generator 13 shown in FIG. 6 receives the electrical signal output from the transducer 25. The signal generator 13 outputs such an electric signal. The converter 14 receives such an electric signal.

  The signal generator 13 shown in FIG. 6 includes a generator 27, a direction matching unit 28, and an amplifier 29. The processing unit 15 outputs a radiation instruction signal. Generator 27 receives a radiation indication signal. The generator 27 generates an electrical signal based on the radiation instruction signal. The electrical signal includes drive waveform information.

  The drive waveform is information necessary for driving the transducer 25 shown in FIG. When the transducer 25 is driven, a sound wave is emitted. The drive waveform is a waveform of a sound wave emitted from the transducer 25.

  The generator 27 shown in FIG. 6 outputs an electrical signal. Direction aligner 28 receives such an electrical signal. The generator 27 further outputs a trigger signal. The trigger signal has information on the time when the generator 27 outputs the electrical signal. The amplifier 29 receives the trigger signal. The amplifier 29 receives the trigger signal.

  The directional matcher 28 shown in FIG. 6 is connected to the generator 27, the amplifier 29, and the transducer 25. The direction matching unit 28 outputs the electrical signal received from the generator 27 to the transducer 25. The direction matching unit 28 outputs the electrical signal supplied from the transducer 25 to the amplifier 29. The direction matching unit 28 adjusts the transmission direction of these signals. For this reason, the electrical signal output from the generator 27 is not output to the amplifier 29.

  The amplifier 29 shown in FIG. 6 receives an electrical signal from the direction matching unit 28. This electric signal is an electric signal originally output from the transducer 25. The amplifier 29 amplifies the high frequency component in the supplied electric signal with a predetermined amplification factor. The amplifier 29 outputs an electrical signal. The converter 14 receives such an electric signal.

  In the electric signal, a high frequency component is amplified. An example of the high frequency component is a component of 1 MHz to 100 MHz. Such a component is necessary to calculate the loss tangent of the test piece 43 that vibrates with a high frequency.

  The amplifier 29 shown in FIG. 6 starts receiving the electrical signal supplied from the direction matching unit 28 after receiving the trigger signal from the generator 27. The amplifier 29 shown in FIG. 6 does not receive an electrical signal unless it receives a trigger signal. The amplifier 29 does not perform unnecessary operations other than reception of electrical signals.

  The conversion unit 14 illustrated in FIG. 6 performs conversion of the signal format of information transmitted and received between the processing unit 15 and the others. The conversion unit 14 includes a D / A conversion unit 30 and an A / D conversion unit 31.

  The D / A converter 30 shown in FIG. 6 includes a D / A converter circuit (converter). The D / A converter 30 converts the digital control signal output from the processor 15 into an analog signal. The D / A converter 30 outputs an analog signal. The control unit 10 receives an analog signal. Part of the analog signal is a radiation instruction signal. Generator 27 receives a radiation indication signal.

  The A / D conversion unit 31 illustrated in FIG. 6 includes an A / D conversion circuit (converter). The A / D converter 31 converts the electrical signal output from the amplifier 29 into a digital signal. Such an electrical signal is originally an analog signal. The A / D converter 31 outputs a digital signal. The processing unit 15 receives a digital signal.

  The A / D converter 31 shown in FIG. 6 converts the electrical signal output from the sensor 24 into a digital signal. Such an electrical signal is originally an analog signal. The A / D converter 31 outputs a digital signal. The processing unit 15 receives a digital signal.

  The processing unit 15 illustrated in FIG. 6 calculates the loss tangent. The loss tangent varies depending on the vibration frequency of the test piece 43. The electrical signal is sent from the ultrasonic radiation unit 12 to the processing unit 15 via the signal generation unit 13 and the conversion unit 14. The processing unit 15 calculates the loss tangent of the test piece 43 using the electrical signal.

  The processing unit 15 includes, for example, a computer, preferably a personal computer. The computer includes a memory and a CPU. The computer operates with a program. The program is loaded into the memory and executed by the CPU. Information necessary for the operation of the processing unit 15 can be described in a program.

  The program may be stored using various types of non-transitory computer readable media and supplied to a computer. Non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer-readable media include magnetic recording media (for example, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (for example, magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / W and semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (random access memory)) are included. The program may also be supplied to the computer by various types of transitory computer readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

  The processing unit 15 shown in FIG. 6 outputs a control signal. The control unit 10 receives a control signal. The processing unit 15 stores information on the strain of the test piece 43. Strain information is included in the control signal. The processing unit 15 receives a digital signal.

  The digital signal includes a digital signal generated by converting an analog signal output from the sensor 24 shown in FIG. Such a digital signal includes information on the phase of the stress acting on the test piece 43. Based on these pieces of information, the processing unit 15 calculates a loss tangent exhibited by the test piece 43 that vibrates at a low frequency.

  The processing unit 15 shown in FIG. 6 performs a waveform analysis process in a predetermined frequency region. Such analysis processing may be FFT (Fast Fourier Transformation) processing. The predetermined frequency region is a region including a frequency whose loss tangent is to be measured.

  The processing unit 15 shown in FIG. 6 acquires the amplitude and phase from the strain information. Strain information is included in the control signal. The processing unit 15 receives a digital signal. The digital signal includes a digital signal generated by converting the analog signal output from the amplifier 29. Such a digital signal includes information on the temporal change of the waveform of the sound wave reflected by the test piece 43. Based on these pieces of information, the processing unit 15 calculates the loss tangent exhibited by the test piece 43 that vibrates at a high frequency.

[DMA measurement and processing]
The processing unit 15 shown in FIG. 6 compares the phase of stress acting on the test piece 43 and the phase of strain of the test piece 43. The processing unit 15 calculates the phase difference between them. The processing unit 15 calculates the loss tangent exhibited by the test piece 43 that vibrates at a low frequency from the phase difference. Such calculation can be performed by a known method.

[Ultrasonic measurement and processing]
<Assistance>
All the description contents described in Patent Document 2 and Japanese Patent Application Publication No. 2007-047130 are incorporated.
<Surface reflection method>
As shown in FIG. 7, the ultrasonic measurement is performed by the surface reflection method. In the ultrasonic measurement, measurement of a reference value and measurement of a value exhibited by the test piece 43 are performed. When measuring the reference value, the surface of the retarder 26 is not in contact with the test piece 43. When measuring the value exhibited by the test piece 43, the surface of the retarder 26 is in contact with the test piece 43. In any case, the surface of the retarder 26 is in contact with the transducer 25.

  The transducer 25 shown in FIG. 7 radiates an incident sound wave 47 to the test piece 43. The incident sound wave 47 is a sound wave incident on the test piece 43 from the delay material 26. When the delay material 26 and the test piece 43 are not in contact with each other, the incident sound wave 47 is a sound wave that enters the air from the delay material 26.

  As shown in FIG. 7, a part of the emitted incident sound wave 47 is reflected at the interface between the delay material 26 and the test piece 43. The remainder of the incident sound wave 47 is transmitted through the interface. The ratio between reflection and transmission is represented by the reflectance of the interface. The reflectivity depends on the difference in acoustic impedance between the delay material 26 and the test piece 43. When the delay material 26 and the test piece 43 are not in contact with each other, the emitted incident sound wave 47 is almost totally reflected at the interface between the delay material 26 and air. The case where the delay member 26 and the test piece 43 are not in contact includes the case where the test piece 43 is not arranged in the measuring apparatus 1.

  As shown in FIG. 7, the reflected incident sound wave 47 becomes a reflected sound wave 49. When the delay material 26 and the test piece 43 are in contact with each other, the reflected sound wave 49 is a sound wave reflected by the test piece 43. When the delay member 26 and the test piece 43 are not in contact, the reflected sound wave 49 is a sound wave reflected by air. The measuring device 1 performs ultrasonic measurement based on the reflected sound wave 49.

  The transducer 25 shown in FIG. 7 receives the reflected sound wave 49. The transducer 25 converts the reflected sound wave 49 into an electric signal. The amplifier 29 shown in FIG. 6 amplifies high frequency components in the electric signal. The A / D converter 31 converts the electric signal into a digital signal.

  The reference value and the value presented by the test piece 43 shown in FIG. 7 are stored in the processing unit 15 shown in FIG. 6 after undergoing these conversions. The reference value and the value presented by the test piece 43 include an ultrasonic phase and amplitude value at a predetermined frequency. These are all functions of frequency. The processing unit 15 compares the value provided by the test piece 43 with the reference value to the processing unit 15 to calculate the loss tangent of the test piece 43.

<Measurement of Reference Value and Value Presented by Specimen 43>
The measuring apparatus 1 shown in FIG. 6 measures the reference value before or after measuring the value presented by the test piece 43. The reference value can be measured according to the method described in Patent Document 2. The value exhibited by the test piece 43 can be measured according to the method described in Patent Document 2. The frequency and amplitude of the incident sound wave 47 when measuring the value exhibited by the test piece 43 are the same as the frequency and amplitude of the incident sound wave 47 radiated when measuring the reference value.

<Calculation of loss tangent>
The loss tangent can be calculated according to the method described in Patent Document 2. The processing unit 15 shown in FIG. 6 uses the real number and phase of the amplitude value in the reference value. The processing unit 15 compares the amplitude and phase of the reflected sound wave 49 reflected by the test piece 43 with the reference value. The comparison is performed based on the method described in Patent Document 2. By this arithmetic processing, the measuring apparatus 1 can measure the loss tangent exhibited by the test piece 43.

  The above-described DMA measurement and ultrasonic measurement, and the arithmetic processing associated therewith, can be performed using a contract test service provided by High Frequency ViscoElasticity Corporation, Yokohama, Kanagawa, Japan.

[Tire design method]
As described above, the loss tangent varies depending on the strain and frequency in the tread vibration.
Tire hysteresis loss depends on tire loss tangent. Therefore, the hysteresis loss of the tire depends on the frequency in the tread vibration. That is, the tire hysteresis loss has frequency characteristics. Tire hysteresis loss depends on the amount of strain in tread vibration. Furthermore, the frequency characteristics of tire hysteresis loss vary depending on the magnitude of strain.

  A tire design method for controlling the frequency characteristics of tire hysteresis loss will be described. The tire includes a rubber containing a reinforcing material or a reinforcing agent (hereinafter referred to as a reinforcing material). The reinforcing material may be one or more of silica and carbon black. Such reinforcing materials are agglomerated with each other. The reinforcing material forms a granular aggregate like a bunch of grapes. In such agglomerates, each grain in the bunch of grapes is considered as one or several molecules of reinforcing material. The reinforcing material is not dispersed in the rubber. Each agglomerate is dispersed in the rubber.

  When such rubber undergoes large deformation, the hysteresis loss of rubber is more likely to occur than when rubber undergoes small deformation. Such hysteresis loss may occur due to the interaction between the reinforcing materials. Hysteresis loss may occur due to interaction between rubber molecules and the reinforcing material. As described above, in this embodiment, the loss tangent changes according to the frequency. Due to the above interaction, the peak frequency and the magnitude of the loss tangent at the peak frequency change.

  Such an effect is also called a pain effect. For example, in a rubber material in which hysteresis loss becomes dominant as strain increases, the rolling resistance of the tire increases and the grip performance of the tire improves. In the rubber material in which hysteresis loss becomes inferior as the strain of the rubber decreases, the rolling resistance of the tire decreases and the grip performance of the tire decreases. In the present embodiment, a predetermined material rubber may be adopted to develop such a pane effect in the tire, and the tire structure may be designed as predetermined.

  In the present embodiment, when the tire receives a strong stress from the road surface and generates a large strain, the tire has a strong hysteresis loss due to the pain effect. For this reason, a large frictional force is generated in the tire. The time when the tire receives a strong stress from the road surface includes the time when the tire accelerates, decelerates and turns. Moreover, the case where the tire slips with respect to the road surface while the tire performs these operations is included.

  At other times, the hysteresis loss is weakened by the pain effect. The tire according to the present embodiment exhibits a large grip resistance during acceleration, deceleration and turning, and exhibits a small rolling resistance at other times.

[Tire manufacturing method]
The tire manufacturing method for controlling the frequency characteristic of the hysteresis loss of a tire is shown. As an example, a styrene-butadiene copolymer and silica are mixed. At this time, no silica dispersion aid is added. Examples of silica dispersing aids are carboxylic acid amine salts (Patent Document 3, paragraph 0088) and amino / mercaptan co-alkoxy modified silsesquioxanes (Patent Document 4, paragraph 0061).

  The ends of the styrene-butadiene copolymer are not functionalized. For example, the following aspects are mentioned. The copolymerization reaction of styrene and butadiene is not stopped by ethylene sulfide or chlorotriethoxysilane. Instead, the copolymerization reaction is stopped with isopropanol (Patent Document 5, paragraph 0071). Alternatively, no alkoxysilyl group is added to the terminal of the styrene-butadiene copolymer (Non-patent Document 3, Table 1-3).

  In Non-Patent Document 3, the contribution to the pain effect is confirmed by applying low-frequency vibration to a test piece having such a composition. In Non-Patent Document 3, low-frequency vibration means that a strain of 0.1 to 10% is periodically applied at a frequency of several Hz.

  Sulfur is added to the mixture of styrene-butadiene copolymer and silica. The mixture added with sulfur is formed into a tread according to a known method. A tread and other members are assembled according to a known method to obtain a tire.

[Modification of Embodiment]
The vibration applied to the test piece in the DMA measurement described above is a continuous vibration represented by a sine wave (sine wave). In the DMA measurement, a short-time vibration represented by a pulse wave may be used instead of the vibration (Non-patent Document 4). The distortion in such a pulse wave is equivalent to the distortion described with reference to FIGS. Non-Patent Document 4, C. Wrana, U. Eisele und S. Kelbch, "Measurement and Molecular Modeling of Rolling Resistance in Tire Treads", [online], KGK Kautschuk Gummi Kunststoffe 53. Jahrgang, Nr. 3/2000, p. All descriptions described in 126-128 are incorporated.

  As shown in FIG. 1, the test object is a test piece 43. The test object can be replaced with a tire from the test piece. In such a case, an ultrasonic stress wave is generated in the tread by radiating an ultrasonic pulse wave to the tire tread to measure the viscoelasticity of the tire. Such a measurement mode is called a so-called surface method. The strain in the surface method is equivalent to the strain described based on FIG. The difference is that the test piece was replaced with a tread.

  The loss tangent exhibited by the test piece 43 shown in FIG. 6 depends on the frequency. Therefore, the measuring apparatus 1 may measure the loss tangent for each different frequency. The ultrasonic measurement may be performed by a bottom reflection method.

  The transducer 25 shown in FIG. 6 may be divided into a transmitter and a receiver. The transmitting unit may transmit a powerful ultrasonic wave as the incident sound wave 47. The frequency band of high intensity ultrasonic waves may be narrower than the frequency band of ultrasonic waves for measurement. The transmitter may be configured as a plurality of transmitters having a plurality of bands. The receiving unit may receive ultrasonic waves for measurement as the reflected sound waves 49. The frequency band of measurement ultrasonic waves may be wider than the frequency band of powerful ultrasonic waves. The receiving unit may be configured as a plurality of receiving units having a plurality of bands.

  The processing unit 15 illustrated in FIG. 6 and other components may be separated. A control signal may be sent to the conversion unit 14 from outside the measurement apparatus 1. A digital signal may be sent from the conversion unit 14 to the outside of the measuring apparatus 1. Communication between the conversion unit 14 and the outside of the measuring apparatus 1 may be performed using a network. The network may be the Internet. The loss tangent may be calculated outside the measuring apparatus 1.

  Thus, a tire having viscoelasticity optimized by strain and frequency achieves both a small rolling resistance and a large grip performance. Small rolling resistance is generally associated with improved fuel economy. Large grip performance generally contributes to improved safety and comfort.

  FIG. 8 is a view showing a vehicle 60 equipped with a tire 65 having a sensor. The tire 65 is equivalent to the above tire. In the vehicle 60, the performance of the tire 65 can be further enhanced by using a sensor provided in the ABS 68 (anti-brake lock system) provided in the vehicle 60.

  The sensor included in the ABS 68 shown in FIG. 8 is a sensor having a function of at least one of a slip sensor and an acceleration sensor. With such a configuration, the tire 65 can be used under a strain condition in which the maximum performance of the tire 65 can be exhibited.

  The tire 65 shown in FIG. 8 may further incorporate a sensor 66 having a strain gauge. The sensor 66 is a sensor system that measures strain and viscoelasticity of the tire 65. With such a strain gauge, the performance of the tire 65 can be further enhanced. A well-known strain gauge can be used.

  The vehicle 60 shown in FIG. 8 further includes a control device 62. The control device 62 can send and receive information to and from the ABS 68. The control device 62 can transmit and receive information to and from the sensor 66 wirelessly. The sensor 66 transmits strain and viscoelasticity data relating to the tire 65 obtained based on the measurement to the control device 62. The control device 62 may be a comprehensive vehicle control device that controls other functions of the vehicle 60.

  The control device 62 shown in FIG. 8 includes a program storage unit 63 and a data storage unit 64. The program storage unit 63 stores a control program. The control device 62 calls a control program and operates based on the control program. The control device 62 stores the data received from the sensor 66 in the data storage unit 64.

  The tire 65 shown in FIG. 8 has optimized viscoelasticity. In order to bring out the performance of the tire 65, it is preferable to use viscoelasticity information. The above data and viscoelasticity information related to the tire 65 can be combined. The data storage unit 64 may store viscoelastic information in advance. The acceleration in braking and acceleration of the vehicle can be controlled by a combination of the control device 62 and surrounding sensors.

  As an application of the vehicle control method shown in FIG. 8, a traffic control system 61 that controls traffic in a region where the vehicle 60 travels can be made using this. The traffic control system 61 includes a server 67 provided outside the vehicle 60. The server 67 can transmit and receive information to and from the control device 62 wirelessly. The traffic control system 61 can reflect the deterioration information of the tire 65 in the traffic control.

  A server 67 shown in FIG. 8 optimizes a travel plan between the vehicle 60 and vehicles in the area around the vehicle 60. For this reason, these vehicles can reach the target value in a minimum time. It is preferable that the vehicle in the area around the vehicle 60 also has a function equivalent to that of the vehicle 60. Hereinafter, these vehicles are collectively referred to as a vehicle 60 unless otherwise specified.

  The server 67 shown in FIG. 8 refers to information on the rolling resistance and grip of the tire against the strain of the tire mounted on the vehicle 60. Such information is stored in the server 67. The server 67 transmits a signal for controlling acceleration, braking, and traveling speed of the vehicle 60 to the control device 62 provided in the vehicle 60 based on the above reference. The control device 62 controls the vehicle based on the signal. The traffic control system 61 can reduce fuel consumption between the vehicle 60 and vehicles in the area around the vehicle 60.

  The tire 65 shown in FIG. 8 deteriorates with time and repeated use. The traffic control system 61 can reflect the deterioration information of the tire 65 in the traffic control.

  The sensor 66 shown in FIG. 8 may have a function equivalent to a known strain sensor. Data related to changes in the hardness of the tire 65 may be collected by the sensor 66 and stored in the data storage unit 64. The control device 62 may update the viscoelasticity information in consideration of the deterioration of the tire 65 using such information.

  The sensor 66 shown in FIG. 8 may have a function equivalent to that of the tire visceral sensor according to the ultrasonic viscoelasticity measuring apparatus and method described in Patent Document 2. Data relating to changes in viscoelasticity of the tire 65 may be collected by the sensor 66 and stored in the data storage unit 64. The control device 62 may update the viscoelasticity information in consideration of the deterioration of the tire 65 using such information.

  Regarding the above-described control, Patent Document 2, Japanese Patent Application Publication, JP-A-2007-047130; Non-Patent Document 5, Ryosuke Matsuzaki, “Development of Sensor-Free Wireless Strain Measurement Smart Tire”, [online], KAKEN Database of Grants-in-Aid for Scientific Research, Internet <URL: https://kaken.nii.ac.jp/d/p/06J05708.en.html>; Developed by Bridgestone, a sensor technology that uses tires to the end (2/4) ", [online], November 14, 2014, MONOist, Internet <URL: http://monoist.atmarkit.co.jp/ mn / articles / 1411/14 / news153_2.html> is incorporated in full.

[Design example]
FIG. 9 is a graph showing a tire design example. The graph represents the relationship between frequency, distortion and loss tangent. The x axis represents frequency. The curve in the graph is represented in the frequency range of 10 Hz to 1 GHz. The y axis represents the magnitude of strain. The curves in the graph are expressed in the range of strain of 0.1% to 10%. The z axis represents the loss tangent.

As shown in FIG. 9, the present design example simulates a tire that exhibits a high loss tangent when vibrating at high frequencies. High frequency vibration is vibration of 0.1 MHz or more and 1 × 10 ² MHz or less. This design example mimics a tire that exhibits a low loss tangent when vibrating at low frequencies. In this design example, the low-frequency vibration is vibration of 1 Hz or more and 1 × 10 ² Hz or less. In a preferred embodiment, the tire of this design example exhibits the above properties regardless of temperature.

  In the above, the temperature when the tire vibrates at a high frequency and the temperature when the tire vibrates at a low frequency may be the same. Such a temperature may be from -30 ° C to 60 ° C. The temperature may be any of -25, -20, -15, -10, -5, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, and 55 ° C.

  In the above, the temperature at which the tire vibrates at a high frequency and the temperature at which the tire vibrates at a low frequency may both be within a certain range. Such fixed ranges may be any of -30 ° C to 60 ° C, -20 ° C to 50 ° C, -10 ° C to 40 ° C, 0 ° C to 30 ° C, 10 ° C to 20 ° C.

  Vibration means that the tire is periodically deformed with a predetermined magnitude of strain. The magnitude of strain refers to the amount of deformation of the tire per unit length of the tire. In this design example, the frequency characteristic of tire hysteresis loss can be controlled by the magnitude of strain. The frequency characteristic of hysteresis loss means that the loss tangent of a tire changes according to the frequency when the tire vibrates at various frequencies.

  A state 44 shown in FIG. 9 shows a state most excellent in wet grip. In state 44, the distortion is large and the frequency is high. In state 44, the distortion is 10% and the frequency is 1 MHz. Therefore, in state 44, it can be said that the tread vibrates in the second frequency band with the second strain.

  A state 45 shown in FIG. 9 shows a state where the rolling resistance is the lowest. That is, the state 45 shows the state with the best fuel consumption. In state 45, the distortion is small and the frequency is low. In state 45, the strain is 0.1% and the frequency is 10 Hz. Therefore, in state 45, it can be said that the tread vibrates at the first frequency with the first strain.

  It can be said that the loss tangent in the state 44 shown in FIG. 9 is the second loss tangent. It can be said that the loss tangent in the state 45 is the first loss tangent. In state 44, the loss tangent is 1.2. In state 45, the loss tangent is 0.02. The loss tangent in state 44 is 60 times the loss tangent in state 45. Therefore, the tire of this design example exhibits a large grip resistance during acceleration, deceleration and turning, and exhibits a small rolling resistance at other times.

  FIG. 10 is a graph showing the relationship between frequency and loss tangent in a design example. These relationships are expressed for each magnitude of strain. The x axis represents frequency. The z axis represents the loss tangent. The contents represented by the graph are the same as in FIG.

The state 44 shown in FIG. 10 is in the high frequency band 34. The band 34 is included in the range of 0.1 MHz to 1 × 10 ² MHz. State 45 is in the vicinity of the low frequency band 35. The band 35 and the state 45 are included in the range of 1 Hz or more and 1 × 10 ² Hz or less.

[Comparative Example 1]
FIG. 11 is a graph showing Comparative Example 1 of tire design. The z-axis and x-axis of the graph conform to FIG. Moreover, the notation of the magnitude of the strain also conforms to FIG. Comparative Example 1 imitates a conventional tire in which the grip between the road surface and the tire is enhanced.

  The tire shown in FIG. 11 exhibits a high loss tangent in the band. However, such a tire also exhibits a high loss tangent in the band 35. For this reason, the hysteresis loss of the tire is large even if the frequency is low. Therefore, the tire of this comparative example exhibits a large rolling resistance when the tire rolls linearly at a constant speed. Since the Payne effect is small, there is little change due to distortion of the loss tangent peak frequency.

[Comparative Example 2]
FIG. 12 is a graph showing Comparative Example 2 of tire design. The z-axis and x-axis of the graph conform to FIG. Moreover, the notation of the magnitude of the strain also conforms to FIG. Comparative Example 1 imitates a tire with low rolling resistance.

  The tire shown in FIG. 12 exhibits a low loss tangent in the band 35. However, such tires also exhibit a low loss tangent in band 34. For this reason, the hysteresis loss of the tire is small even if the frequency is high. Therefore, the tire of this comparative example shows only a small grip resistance when accelerating, decelerating and turning.

  Compared with the tire of Comparative Example 1 shown in FIG. 11, the tire of the design example shown in FIG. 10 exhibits a small rolling resistance. Compared with the tire of Comparative Example 2 shown in FIG. 12, the tire of the design example shown in FIG. 10 exhibits higher grip performance. The designed tire has both high grip performance and low rolling resistance.

[Example of apparatus for shear deformation of test piece]

  The measuring device 70 shown in FIG. 13 periodically shears and deforms the test piece 43. The measuring device 70 includes a driving device 71. The drive device 71 is a servo motor drive device. The driving device 71 further includes a slider 72 and a servo 73. The slider 72 is connected to the servo 73. The servo 73 supplies driving power to the slider 72 and controls its movement.

  The slider 72 shown in FIG. 13 has a flat upper surface 74. The slider 72 reciprocates in parallel with the upper surface 74. Accordingly, the surface 42 is displaced in a direction parallel to the surface 42. The surface 42 of the test piece 43 is in contact with the upper surface 74 of the slider 72. Therefore, the test piece 43 undergoes shear deformation in a direction parallel to the surface 42. For this reason, shear strain occurs in the test piece 43. Shear deformation is repeated. Therefore, the test piece 43 vibrates with shear strain.

  A motor (not shown) is attached to the slider 72 shown in FIG. The motor receives driving power and reciprocates the slider 72. An example of such a motor is a linear motor. Another example of such a motor is a rotary motor. The rotary motion of the rotary motor can be converted into a reciprocating motion by a lead screw.

  The measurement apparatus 70 shown in FIG. 13 further includes an ultrasonic radiation unit 12. The ultrasonic radiation unit 12 is an ultrasonic sensor for measuring high-frequency viscoelasticity of the test piece 43 by radiating high-frequency sound waves to the test piece 43 as described above.

  The processing unit 15 illustrated in FIG. 13 includes a PIX (PCI eXtentions for Instrumentation) system 16. PXI is a registered trademark. PCI stands for Peripheral Component Interconnect. The PXI system 16 includes I / O (Input / Output), ADC (Analog to Digital Converter), MPU (Micro-processing Unit), and HDD (Hard Disk Drive).

  The HDD shown in FIG. 13 holds information on the frequency and amplitude of the reciprocating motion of the slider 72. The frequency corresponds to the rate of change of shear strain. The amplitude corresponds to the magnitude of the shear strain. The servo 73 is connected to the I / O. The MPU generates a control signal based on information stored in the HDD. The PIX system sends a control signal to the servo 73 through I / O. The servo 73 controls the slider 72 according to the control signal.

  The ultrasonic radiation unit 12 illustrated in FIG. 13 operates in the same manner as the ultrasonic generation unit 12 illustrated in FIG. The ultrasonic radiation unit 12 radiates ultrasonic waves to the test piece 43 based on the electrical signal generated by the signal generation unit 13. At the same time, the ultrasonic radiation unit 12 receives reflected waves and the like. The signal generator 13 is connected to the ADC. The ADC receives analog information related to high-frequency viscoelasticity from the ultrasonic radiation unit 12 via the signal generation unit 13 in the same manner as the conversion unit 14 shown in FIG. The ADC converts analog information into digital information. The processing unit 15 records digital information on the HDD. The HDD holds digital information. The MPU controls the processing of such information. Part or all of the processed information is displayed on the display 18.

  The measuring device 70 shown in FIG. 13 may transmit information recorded on the HDD or information held by the HDD to an external device via a wired or wireless communication network. On the contrary, the measuring device 70 may receive information from an external device. Such information may be recorded on the HDD. Such information may be held by the HDD. The HDD may be another storage device such as a flash memory.

  The upper curve 75a-d of the graph shown in FIG. 14 represents the strain vibration in the DMA measurement. Lower curves 77a-f represent viscoelasticity measurements. The graph as a whole represents the relationship between strain vibration and viscoelasticity measurements. The horizontal axis of the graph represents time. In the strain vibration curve 75a-d, the vertical axis of the graph indicates the magnitude of the shear strain in the DMA measurement. The value of the shear strain is the same value as the shear strain γ described with reference to FIG. 4 and Table 3 as described above. The shear strain γ is represented by the ratio (amplitude Δs / test specimen thickness t) between the amplitude Δs of the surface 42 and the specimen thickness t shown in FIG. The strain vibration is vibration accompanied by the above-described shear strain γ as shown by an arrow in FIG.

  In the curve 75a-d shown in FIG. 14, the strain change rate is 0.01 Hz to 100 Hz. The strain change rate is the reciprocal of the period of strain vibration.

  In the curve 75a-d shown in FIG. 14, the shear strain γ is 1 to 100%. The shear strain γ is a percentage of the amplitude Δs with respect to the specimen thickness t. The shear strain γ of the curve 75a is the smallest, and the shear strain γ increases in the order of the curves 75b, c, and d.

  In the viscoelasticity measurement curve 77a-f shown in FIG. 14, the vertical axis of the graph represents the variable E ′, the variable E ″, and the loss tangent tan δ.

  The variable E ′ shown in FIG. 14 is related to the viscoelasticity measurement curve. The variable E ′ represents the storage elastic modulus E ′. The storage elastic modulus E ′ is an ultrasonic elastic modulus.

  The variable E ″ shown in FIG. 14 relates to the viscoelasticity measurement curve. The variable E ″ represents the loss elastic modulus E ″. The loss elastic modulus E ″ is the ultrasonic elastic modulus.

The relationship among tan δ, variable E ′, and variable E ″ shown in FIG. 14 is expressed as follows.
tan δ = E ″ / E ′

  Curves 77a-f shown in FIG. 14 represent vibrations having different magnitudes. The shear strain γ when the curve 77a is obtained is the smallest, and the shear strain γ increases in the order of the curves 77b, c, d, e, and f. The graph shows that the ultrasonic viscoelasticity increases as the shear strain γ increases. The shear strain γ when the curves 77a-f are obtained is the shear strain γ of the curves 75a-f, respectively.

  The frequency of the ultrasonic wave can be arbitrarily set according to the required characteristics of rubber products such as tires.

  The relationship between the measurement device 70 shown in FIG. 13 and the strain vibration and viscoelasticity measurement values shown in FIG. 14 is expressed as follows. That is, in the measuring device 70, the magnitude of the shear strain γ, the frequency of strain vibration, and the pressing force of the ultrasonic sensor can be arbitrarily set. For this reason, in addition to the measurement of the viscoelasticity property under the vibration of the low frequency shear strain, the variable affecting these can be arbitrarily changed when measuring the high frequency viscoelasticity due to the ultrasonic wave propagation. Therefore, it is suitable for comparing and examining the relationship between the viscoelastic characteristics under the vibration of the low frequency shear strain and the high frequency viscoelasticity measured at the time of ultrasonic wave propagation.

[Test Example 1 using a tire as a test piece]

  The test example which uses a tire as a test piece is shown below. FIG. 15 shows a method for testing a tire 81 mounted on a car body 80 of an automobile. The tire 81 is attached to the wheel 82. The wheel 82 is attached to the vehicle body 80 of the automobile. A pressing force 79 is applied to the tire 81. The pressing force 79 is a pressing force derived from the weight of the vehicle body 80.

  The tread surface 86 of the tire 81 shown in FIG. 15 is in contact with the sensor 83. The tread surface 86 is a contact surface of the tire 81. The sensor 83 is an ultrasonic sensor used for high frequency viscoelasticity measurement. The sensor 83 has the same function and configuration as the ultrasonic radiation unit 12 shown in FIG.

  FIG. 15 shows a slider mechanism 84. The slider mechanism 84 is driven by a servo motor drive device (not shown). The slider mechanism 84 vibrates the sensor 83 in parallel with the contact surface between the tire 81 and the sensor 83.

  The vibration direction of the sensor 83 shown in FIG. 15 may be parallel to the rolling direction of the tire 81 on the sensor 83. When the sensor 83 is viewed in plan, the direction of vibration may be shifted by a predetermined angle with respect to the rolling direction of the tire 81. The vibration of the sensor 83 may be dynamic. The sensor 83 may be static without vibrating. Static means that a shearing force is applied to the tire 81 only in one direction with a very small motion at an extremely low speed near the tread surface 86.

  When testing the tire 81 shown in FIG. 15, the vehicle body 80 or the wheel 82 is fixed. When the wheel 82 is fixed, the vehicle body 80 may be omitted. Instead of the pressing force 79, another pressing force may be applied to the tire 81 or may not be applied. When the sensor 83 vibrates in a state where the vehicle body 80 is fixed, the tread surface 86 vibrates in the tangential direction of the tread surface 86. Such vibration repeatedly applies shear strain to the tire 81.

  The tire 81 may be vibrated without using the slider mechanism 84 shown in FIG. That is, the tire 81 may be vibrated by vibrating the vehicle body 80 while fixing the sensor 83. The vibration may be generated by pushing the vehicle body 80 intermittently. On the other hand, the tire 81 is in contact with the sensor 83. For this reason, the tire 81 is not displaced on the tread surface 86. Therefore, strain vibration is applied to the tire 81. For this reason, shear strain is repeatedly applied to the tire 81.

  The tire 81 may be vibrated by driving the tire 81 shown in FIG. The driving of the tire 81 may be static or vibrational. The driving of the tire 81 being static means that the driving of the tire 81 causes a shearing force to be applied to the tire 81 only in one direction with a very small movement at an extremely low speed near the tread surface 86. Represent. The expression that the driving of the tire 81 is oscillatory means that the driving of the tire 81 is periodically repeated.

  The amount of shear strain of the tire 81 shown in FIG. 15 is measured. The strain amount is a percentage of the deformation amount Δs with respect to the specimen thickness t. Represents. You may measure the shear deformation force (shear deformation force) at the time of a shear strain generating in the tire 81. The shear deformation force represents a tangential force acting on the tread surface 86.

  In the test of the tire 81 shown in FIG. 15, the position of the sensor 83 may be adjusted according to the shape of the tire 81. For example, the position of the sensor 83 may be adjusted so that the tread block (not shown) on the tread surface 86 and the sensor 83 are in close contact with each other. Further, the position of the sensor 83 may be adjusted in accordance with the size of the tire 81. Instead of adjusting the position of the sensor 83, or simultaneously with the adjustment of the position of the sensor 83, the position of the tire 81 may be adjusted. These adjustments may be performed using a predetermined position adjustment mechanism described later.

[Test Example 2 using a tire as a test piece]

  FIG. 16 represents a measuring device 89 for testing a tire. The measuring device 89 is a device for measuring low-frequency and high-frequency viscoelastic properties. The measuring device 89 calculates the high frequency viscoelastic property of the tire 81 by the surface reflection method. The measuring device 89 further has a function of measuring the tire 81 optically.

  In FIG. 16, a tire 81 that is a measurement sample and the ultrasonic radiation unit 12 are shown. The ultrasonic radiation unit 12 includes a transducer 25 and a delay material 26. The measuring device 89 has a configuration equivalent to that of the measuring device 1. The measuring device 89 further includes a light source 90, a camera 91, and a processing unit 92. An example of the light source is an LED (Light Emitting Diode). An example of the camera 91 is a high-speed CCD (Charge Coupled Device) camera. The processing unit 92 is connected to the camera 91 by wire or wireless.

  The retarder 26 shown in FIG. 16 has a search surface 87 and a detection surface 88. The search surface 87 faces the tire 81. The detection surface 88 faces the transducer 25. In the drawing, it is emphasized that the tread block located on the tread surface 86 of the tire 81 is in contact with the detection surface 88. The search surface 87 and the detection surface 88 are located at positions facing each other.

  When measuring the viscoelastic characteristics, a pressing force 79 is applied to the tire 81 shown in FIG. The tread surface 86 of the tire 81 comes into contact with a part of the search surface 87 of the delay member 26 by the pressing force 79. And the tire 81 rotates because the motor not shown drives the tire 81. The rotation is performed while the tire 81 contacts a part of the exploration surface 87.

  The tire 81 shown in FIG. 16 is fixed so as to keep in contact with the exploration surface 87 even if the rotation continues. For this reason, the tire 81 is not displaced back and forth in the rolling direction. Friction is generated between the tread surface 86 and the exploration surface 87 by the pressing force 79. A shearing force generated by friction and rotation of the tire 81 acts on the periphery of the tread surface 86.

  The light source 90 shown in FIG. 16 irradiates the measurement light 95 toward the search surface 87. The measuring light 95 passes through the delay material 26. The measurement light 95 is incident on the search surface 87. The measurement light 95 is reflected by the search surface 87 to become reflected light 96. The reflected light 96 passes through the delay material 26. The camera 91 detects the reflected light 96 after passing through the delay material 26. By appropriately selecting the refractive index and shape of the retarder 26, the intensity of the reflected light 96 reaching the camera 91 can be increased.

  The camera 91 shown in FIG. 16 images the area 85a-c where the retarder 26 and the tire 81 are in contact with each other in the exploration surface 87. In the regions 85 a-c, the tread block of the tread surface 86 is in contact with the delay member 26. Further, the camera 91 captures an area 85 d, e in the exploration surface 87 where the delay member 26 and the tire 81 are not in contact with each other. In the regions 85d and e, the retarder 26 faces the gap between the tread blocks of the tread surface 86. The shape and number of tread blocks and regions 85a-e shown in the figure are exemplary.

  By scanning the measurement light 95 shown in FIG. 16 at the time of imaging, the measurement light 95 may be incident on a plurality of regions among the regions 85a-e. The measurement light 95 may be converted into a wide beam so that the measurement light 95 is incident on a plurality of regions among the regions 85a-e.

  The substance in contact with the retarder 26 shown in FIG. 16 has a refractive index different from that of the rubber constituting the tire 81. Such material may be air or water. In this example, the retarder 26 is in contact with air in the regions 85d and e. As long as the shearing force acting on the tire 81 is not hindered, the substance in contact with the retarder 26 in the regions 85d and e is not limited.

A boundary surface between the delay member 26 and the tire 81 is formed in the regions 85a-c shown in FIG. A boundary surface between the retarder 26 and air is formed in the regions 85d and e. As described above, the refractive index of the rubber constituting the tire 81 is different from that of air. Therefore, the critical angle θ ₁ in the regions 85a-c is different from the critical angle θ ₂ in the regions 85d and e. For this reason, the reflectance of the measurement light 95 in the regions 85a-c is different from that in the regions 85d and e.

At the time of imaging, the incident angle In of the measurement light 95 on the exploration surface 87 shown in FIG. 16 is set between the critical angle θ ₁ and the critical angle θ ₂ . The camera 91 detects how much the measurement light 95 is reflected in each of the regions 85a-e. Therefore, in the image obtained by the camera 91, the regions 85a-c and the regions 85d, e can be distinguished from each other.

  The processing unit 92 illustrated in FIG. 16 receives image information from the camera 91. The processing unit 92 identifies which region of the exploration surface 87 is in contact with the tire 81 based on the image information. In the figure, it is identified that the tire 81 is in contact with the regions 85a-c. By summing the areas of the regions 85a-c, the contact area between the retarder 26 and the tire 81 is obtained. The processing unit 92 is composed of the same computer as the processing unit 15. The computer is preferably a personal computer.

  The contact area of the tire 81 may be continuously measured while rotating the tire 81 shown in FIG. At this time, the processing unit 92 may identify a place where the tire 81 slips with respect to the exploration surface 87 and a place where the tire 81 adheres. In the place where the tire 81 slides, the tire 81 and the exploration surface 87 do not contact in a short time. Where the tire 81 adheres, the tire 81 contacts the exploration surface 87 for a long time. For this reason, you may distinguish both locations from the difference in contact time.

  A measuring device 89 shown in FIG. 16 measures the contact area between the delay member 26 and the tire 81. The measuring device 89 measures low-frequency and high-frequency viscoelastic properties. By using the measuring device 89, information on the correlation between the contact area and the viscoelastic property in the tire 81 can be obtained.

  The tire 81 shown in FIG. 16 may be replaced with a sample roller. A measuring roller 89 may be used to measure a sample roller made of rubber. The sample roller may be made of other materials used for rotational purposes.

  It is not necessary to rotate the tire 81 shown in FIG. 16 one or more times. That is, the tire 81 may be rotated only by a predetermined angle within a range where the tire 81 partially slides with respect to the delay member 26. The tire 81 may not be rotated. That is, the tire 81 may be brought into contact with the delay member 26 in a non-rotating state. In these measurement modes, information about the correlation between the contact area and the viscoelastic property in the tire 81 can be obtained.

  The transducer 25 shown in FIG. 16 may not emit incident sound waves for measuring high-frequency viscoelasticity to the tire 81. The transducer 25 may only receive a sound wave that is radiated from the tire 81 and propagates through the delay material 26. The sound wave may be a sound wave derived from the vibration of the tire 81 caused by the slip of the tire 81 on the exploration surface 87.

  The sound wave information is output to the processing unit 92 shown in FIG. 16 via a conversion unit (not shown). Based on the information of the sound wave, the processing unit 92 can measure the vibration state of the tire 81 that is caused by the slip of the tire 81. With this aspect, the measuring device 89 can measure the high-frequency viscoelasticity with higher accuracy than when the incident sound wave is radiated to the tire 81.

  The measuring device 89 shown in FIG. 16 can collect information on the vibration frequency band, spectrum, and waveform. Some of these have prominent features. Based on these pieces of information, the measurement device 89 may determine whether or not the vibration state of the tire 81 is a desired state according to the measurement purpose. The measuring device 89 may particularly determine the vibration state of the tire 81 when the tire 81 is not subjected to frictional force.

  When the vibration state of the tire 81 illustrated in FIG. 16 is a desired state, the measurement device 89 may perform measurement of high-frequency viscoelasticity of the tire 81. Thereby, the conditions for the measurement of high-frequency viscoelasticity can be set to the optimum conditions. In order to make the vibration state of the tire 81 a desired state, the exploration surface 87 may be a friction surface having a surface roughness corresponding to the measurement.

[Position adjustment mechanism]

  The measuring apparatus 89 shown in FIG. 16 may further include a position adjustment mechanism 97. As described above, the processing unit 92 analyzes the image obtained by the camera 91. The processing unit 92 sends a command to the position adjustment mechanism 97 based on the analysis result. The position adjustment mechanism 97 receives a command and moves the transducer 25 in a direction parallel to the search surface 87 based on the command.

  As described above, it is preferable to adjust the position of the sensor 83 in accordance with the shape of the tire 81 shown in FIG. The position adjustment mechanism 97 may move the position of the tire 81 in a direction parallel to the search surface 87 instead of the sensor 83 or together with the sensor 83.

  The present invention has been described above with reference to the exemplary embodiments and various examples, but the present invention is not limited to the above. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the invention.

  This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2015-164402 for which it applied on August 24, 2015, and takes in those the indications of all here.

DESCRIPTION OF SYMBOLS 1 Measuring apparatus, 10 Control part, 11 Rheometer part, 12 Ultrasonic radiation part, 13 Signal generation part, 14 Conversion part, 15 Processing part, 20 Driving part, 21 Axis, 22 Plate, 23 Motor, 24 Sensor, 25 Transducer , 26 delay material, 27 generator, 28 directional matching device, 29 amplifier, 30 conversion unit, 31 conversion unit, 34 band, 35 band, 43 test piece, 44 state, 45 state, 46 start time, 47 incident sound wave, 48 End time, 49 Reflected sound wave, 50 Oscillator, 53 block, 54 Block surface, 55 Friction force, 56 Base surface, 60 Vehicle, 61 Traffic control system, 62 Controller, 63 Program storage unit, 64 Data storage unit, 65 Tire, 66 sensors, 67 servers, 70 measuring devices, 71 driving devices, 72 sliders, 73 servos, 74 Surface, 75a-d curve, 77a-f curve, 79 pressing force, 80 body, 81 tire, 82 wheel, 83 sensor, 84 slider mechanism, 85a-e area, 86 tread surface, 87 measurement surface, 88 surface, 89 measurement Device, 90 light source, 91 camera, 92 processing unit, 95 measuring light, 96 reflected light, 97 position adjustment mechanism

Claims (6)

A method for evaluating characteristics of a tire by measuring a loss tangent exhibited by a tread of the tire,
As the loss tangent, the loss tangent exhibited by the test piece is measured by vibrating a test piece having the same composition as that of the rubber constituting the tread at a predetermined strain magnitude and a predetermined frequency.
By vibrating the test piece at a first frequency with a first strain, the first loss tangent exhibited by the test piece is obtained,
The first strain is a shear strain or a tensile strain,
The shear strain represents the ratio of the amplitude in the tangential direction to the thickness in the normal direction of the surface when the test piece vibrates with shear deformation in the tangential direction of the surface of the test piece,
The tensile strain is represented by the ratio of the amplitude in the normal direction to the thickness in the normal direction when the test piece vibrates with tensile deformation in the normal direction.
Before, after or simultaneously with the acquisition of the first loss tangent, the test piece is vibrated so as to include a second frequency component with a second strain, thereby obtaining a second loss tangent exhibited by the test piece. Acquired,
In the second strain, when an elastic stress wave is generated in the test piece by radiating an ultrasonic pulse wave to the test piece, the elastic stress wave advances in the same time as the duration of the pulse wave. Represents the ratio of the amplitude of the elastic stress wave to the distance to
The second frequency is higher than the first frequency;
After the measurement, it is determined whether the second loss tangent is greater than the first loss tangent.
Method. The first strain is 10% or less,
The second strain is 1% or more and 1 × 10 ² % or less,
The method of claim 1. The first frequency is 1 Hz or more and 1 × 10 ² Hz or less,
The second frequency is included in a range of 0.1 MHz to 1 × 10 ² MHz,
The method according to claim 1 or 2. The elastic stress wave is either a longitudinal wave or a transverse wave,
The method according to claim 1. A method for evaluating characteristics of a tire by measuring a loss tangent exhibited by a tread of the tire,
By vibrating the tread at a first frequency with a first strain, the first loss tangent exhibited by the tread is obtained as the loss tangent.
The first strain is a shear strain or a tensile strain,
The shear strain is represented by the ratio of the tangential amplitude to the normal thickness of the surface when the tread vibrates with shear deformation in the tangential direction of the surface of the tread,
The tensile strain is represented by the ratio of the amplitude in the normal direction to the thickness in the normal direction when the tread vibrates with tensile deformation in the normal direction.
Before or after obtaining the first loss tangent or simultaneously with obtaining the second loss, the tread exhibits the loss tangent as the loss tangent by vibrating the tread so as to include the second frequency component with the second distortion. Get tangent,
The second strain is a distance that the elastic stress wave travels in the same time as the duration of the pulse wave when an elastic stress wave is generated in the tread by emitting an ultrasonic pulse wave to the tread. Represents the ratio of the amplitude of the elastic stress wave to
The second frequency is higher than the first frequency;
After the measurement, it is determined whether the second loss tangent is greater than the first loss tangent.
Method. After the measurement, it is determined whether the second loss tangent is 60 times or more of the first loss tangent.
The method according to claim 1.

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