JP2018119931A - Method of evaluating tire grounding characteristics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of evaluating tire grounding characteristics which can evaluate grounding characteristics of a tire on a flat plate even when the flat plate has predetermined convexoconcave.SOLUTION: A method of evaluating tire grounding characteristics according to the invention includes placing a tire on one surface of a flat plate, applying a predetermined load to the tire or subjecting the tire to a no load condition, irradiating the tire from the other surface of the flat plate or the inside of the flat plate with a terahertz wave having a frequency of 0.1-10 THz, in which the wavelength of the terahertz wave is larger than a roughness average height of at least a portion of the one surface of the flat plate, detecting a reflection wave of the terahertz wave from the tire, and evaluating characteristics of the tire in grounding on the basis of a detected result.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for evaluating tire ground contact characteristics.

  Conventionally, as a method for evaluating the ground contact characteristics of a tire, the tire is placed on a flat plate transparent to visible light, and with a predetermined load applied, visible light is irradiated from below the flat plate, and its reflection Some devices detect light (for example, see Patent Document 1).

Japanese Patent No. 3406643

  Here, the actual road surface is paved with asphalt or concrete, or is non-paved stone, sand, or earth, and since the vehicle runs on these, the ground contact characteristics of the tire on the road surface having predetermined irregularities are improved. It is desirable to evaluate. However, in the above method, when a flat plate having unevenness is used, the unevenness may scatter visible light, and it may be difficult to evaluate the ground contact characteristics of the tire on the flat plate having the unevenness.

  In view of such circumstances, an object of the present invention is to provide an evaluation method for tire ground contact characteristics that can evaluate the ground contact characteristics of a tire on a flat plate even when the flat plate has predetermined irregularities. .

The gist configuration of the present invention is as follows.
The method for evaluating tire ground contact characteristics according to the present invention includes placing a tire on one surface of a flat plate,
A predetermined load is applied to the tire or an unloaded condition is applied, and the tire is irradiated with a terahertz wave having a frequency of 0.1 THz to 10 THz from the other surface side of the flat plate or from the inside of the flat plate. The wavelength of the terahertz wave is, for example, larger than the roughness average height of at least a part of one surface of the flat plate, and the reflected wave of the terahertz wave from the tire is detected, and based on the detection result, It is characterized by evaluating the characteristics of a tire when it contacts the ground. Here, if the unevenness does not scatter terahertz waves, other lengths such as arithmetic mean waviness Wa can be applied to the wavelength of the road surface. Other reference lengths can also be used.
According to this method, even when the flat plate has predetermined irregularities, the ground contact characteristics of the tire on the flat plate can be evaluated.

In the method for evaluating tire ground contact characteristics of the present invention,
Place the tire on one side of the flat plate,
A predetermined load is applied to the tire, or no load is applied,
The tire is irradiated with a terahertz wave having a frequency of 0.1 THz to 10 THz from the other surface side of the flat plate or from the inside of the flat plate, and the wavelength of the terahertz wave is at least one of the one surface of the flat plate. Greater than the arithmetic average roughness Ra defined by JIS B0601 with a reference length of 8 mm, or greater than the arithmetic average roughness Ra defined by JIS B0601 with a reference length of 2.5 mm ,
Detecting a reflected wave of the terahertz wave from the tire;
It is preferable to evaluate characteristics of the tire at the time of contact based on the detection result.
According to this method, the ground contact characteristics of the tire on the flat plate can be evaluated even when the flat plate has irregularities having the predetermined Ra.

In the tire ground contact characteristic evaluation method of the present invention, it is preferable that the reflected wave of the terahertz wave is detected on the surface.
According to this method, it is possible to easily observe the movement of a certain point and easily measure the movement of the tread surface.

In the tire contact property evaluation method of the present invention, a material having an absorption rate or reflectance of the terahertz wave larger or smaller than that of the rubber is attached to the surface of the rubber to be the contact surface of the tire.
It is preferable to include detecting the position of the substance by detecting a position where the intensity of the detected terahertz wave is increased or decreased compared to the surroundings.
According to this method, the movement of the tread surface can be measured more accurately by easily identifying the position of the substance.

In the tire ground contact property evaluation method of the present invention, an image showing a position where the intensity of the detected terahertz wave is increased or decreased as compared to the surroundings is obtained.
It is preferable to derive a distribution of positions of the substance in the ground plane from the acquired image.
According to this method, the movement of the identification point, which is a point to which a substance is attached, can be measured with higher accuracy.

In the tire ground contact property evaluation method of the present invention, the distribution of the position is weighted by the intensity of the reflected wave from the substance, the center of gravity position obtained from the area, the centroid position obtained from the area, and the distribution range It is preferable that at least one of these is included.
According to this method, the movement of the identification point, which is the point to which the substance is attached, can be measured with good accuracy.

  ADVANTAGE OF THE INVENTION According to this invention, even if a flat plate has a predetermined unevenness | corrugation, the evaluation method of the tire ground contact characteristic which can evaluate the ground contact characteristic of the tire on a flat plate can be provided.

It is a figure which shows typically the evaluation apparatus of the tire ground contact characteristic used for the evaluation method of the tire ground contact characteristic on the flat plate which has an example of the predetermined | prescribed unevenness | corrugation concerning one Embodiment of this invention. It is a figure which shows typically the evaluation apparatus of the tire ground contact characteristic used for the evaluation method of the tire ground contact characteristic on the flat plate which has the predetermined unevenness | corrugation of another example concerning one Embodiment of this invention. It is a figure which shows typically the evaluation apparatus of the tire ground contact characteristic used for the tire ground contact characteristic evaluation method on the flat plate which has the predetermined unevenness | corrugation of another example concerning one Embodiment of this invention. It is an example of the image which shows the motion of the identification point which is the point which attached | subjected the substance. It is an example of the image which shows the motion of the identification point which is the point which attached | subjected the substance, and the distribution of the position of an identification point.

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

  FIG. 1 is a diagram schematically illustrating a tire ground contact property evaluation apparatus used in a tire ground contact property evaluation method on a flat plate having predetermined irregularities according to an embodiment of the present invention. As shown in FIG. 1, the tire ground contact characteristic evaluation device 1 includes a flat plate 2, an irradiation device 3 that irradiates a terahertz wave, a force sensor 4, and a reflected wave detection device 5.

  In the present embodiment, the flat plate 2 is an acrylic plate that is transparent to visible light. In this example, the flat plate 2 has an uneven surface simulating an actual road surface formed on one surface (the upper surface in FIG. 1). Further, the flat plate 2 is entirely formed on the other surface (the lower surface in FIG. 1). However, since the unevenness cannot be completely eliminated from an engineering standpoint, in reality, extremely minute unevenness is formed. Specifically, in this example, one surface (the upper surface in FIG. 1) is 10-80 μm in arithmetic average roughness Ra defined by JIS B0601, with a reference length of 8 mm. The arithmetic average roughness Ra is 2.5 to 10 mm. On the other hand, the other surface (the lower surface in FIG. 1) has an average length Ra of a roughness curve element defined by JIS B0601 with a reference length of 0.8 mm, which is 0.1 to 2 μm.

  In the example shown in FIG. 1, the irradiation device 3 is disposed on the lower side (the other surface side) of the flat plate 2, and the one surface (the lower surface in FIG. 1) from the other surface (the lower surface in FIG. 1) side. It is arranged so that terahertz waves can be irradiated toward the (upper surface) side. The irradiation device 3 can be any known device that can irradiate a terahertz wave having a frequency of 0.1 THz to 10 THz.

  In this example, the force sensor 4 places the tire 6 on one surface (the upper surface in FIG. 1) of the flat plate 2 and applies a predetermined load, and the tire 6 is relative to the flat plate 2 on the flat plate 2. It is possible to measure the pressure and shearing force τ when rotating it automatically. In this case, the force sensor 4 may be any known pressure sensor or shear force sensor, or a pressure / shear force sensor that can measure pressure and shear force. In this example, the force sensor 4 is configured to be partially embedded in the flat plate 2. In the present invention, instead of the force sensor 4, a device for measuring other characteristics may be provided, or the force sensor 4 or the like may not be provided.

  The reflected wave detection device 5 detects a reflected wave of the terahertz wave from the tire 6 that is reflected by the tire 6. As the reflected wave detection device 5, any known device can be used. In this example, since the irradiation device 3 is disposed on the lower side of the flat plate 2 and the tire 6 is disposed on one surface of the flat plate 2 (the upper surface in FIG. 1), the reflected wave detection device 5 is provided with terahertz. It arrange | positions in the downward side of the flat plate 2 so that the reflected wave of a wave can be detected. On the other hand, the arrangement of the reflected wave detection device 5 is not limited to this example. In short, the arrangement may be such that the reflected wave of the terahertz wave from the tire 6 can be detected.

  In the method of the present embodiment, as shown in FIG. 1, first, the tire 6 is placed on one surface of the flat plate 2 (the upper surface in FIG. 1), and a predetermined load is applied to the tire 6. In this example, the tire 6 is assembled with a rim, and the rim is, for example, an industrial standard that is effective in the region where the tire is produced and used. In Japan, JEARMA (Japan Automobile Tire Association) YEAR BOOK, Europe In ETRTO (The European Tire and Rim Technical Organization) STANDARDS MANUAL, in the United States TRA (THE TIRE and RIM ASSOCIATION INC.) YEAR BOOK which is described as a standard in the TR In STANDARDDS MANUAL, it refers to “Measuring Rim”, and in TRA ’s YEAR BOOK, “Design Rim”. In addition to Izu, it also includes sizes that can be included in the above industry standards in the future.Examples of “sizes that will be described in the future” are the sizes described as “FUTURE DEVELOPMENTS” in STANDARDS MANUAL 2013 edition of ETRTO. However, in the case of a size not described in the industrial standard, it means a rim having a width corresponding to the bead width of the tire. In this example, the tire 6 assembled with the rim is filled with an internal pressure. For example, the tire is mounted on the applicable rim and the tire has a maximum tire load capacity according to the standard such as JATMA in an applicable size tire. The air pressure corresponding to (maximum air pressure) can be obtained. In addition, in the case of the size not described in the industrial standard, it means the air pressure (maximum air pressure) corresponding to the maximum load capacity defined for each vehicle on which the tire is mounted. Furthermore, the “predetermined load” can be, for example, the tire maximum load capacity of the standard such as JATMA. Alternatively, it can be set arbitrarily according to the purpose of ground contact characteristic evaluation, such as 0.8 times or 0.9 times the maximum tire load capacity. In the present embodiment, a predetermined load is applied to the tire 6. However, for example, when evaluating a ground contact state under no load as a comparison target, the tire 6 may be in an unloaded state. The air can be replaced with an inert gas such as nitrogen gas or the like.

  Next, the tire 6 is rotated relative to the flat plate 2 on the flat plate 2. For the rotation of the tire 6, although not shown, any known device that can rotate the tire 6 around its axis can be used. Further, when the tire 6 is relatively rotated on the flat plate 2, the flat plate 2 may be moved while the tire 6 is stationary so as to be rotatable around the axis. May be rolled on the flat plate 2 with the tire 6 stationary. Further, both the flat plate 2 and the tire 6 may be moved so that the tire 6 is relatively rotated on the flat plate 2. In either case, the irradiation device 3 and the reflected wave detection device 5 can be stationary or moved. In these cases, although not shown, any known device that can move the flat plate 2, the irradiation device 3, the reflected wave detection device 5, and the tire 6 can be used.

  Then, terahertz waves having a frequency of 0.1 THz to 10 THz are applied to the tire 6 from the irradiation device 3 positioned on the other surface (the lower surface in FIG. 1) of the flat plate 2 on one surface (in FIG. 1). Irradiation toward the tire 6 on the upper surface). In this example, the irradiation device 3 is disposed on the lower side (the other surface side) of the flat plate 2. However, the present invention is not limited to this mode. The terahertz wave may be irradiated from the inside of the flat plate 2 toward one surface of the flat plate 2 (the upper surface in FIG. 1).

  Here, in this embodiment, the wavelength of the irradiated terahertz wave (in the case of a terahertz wave having a frequency of 0.1 THz to 10 THz, 0.03 mm to 3 mm) is JIS B0601 of at least a part of one surface of the flat plate 2. It is larger than the arithmetic average roughness Ra defined with a reference length of 8 mm or the arithmetic average roughness Ra with a reference length of 2.5 mm. Thereby, the irradiated terahertz wave is irradiated to the tire 6 on the flat plate 2 without being scattered by the flat plate 2. Moreover, since the wavelength of the terahertz wave is larger than the Ra of the uneven lower surface 4 b, the terahertz wave reflected by the tire 6 can travel downward of the flat plate 2 without being scattered by the flat plate 2.

  Next, a reflected wave of the terahertz wave from the tire 6 is detected by the reflected wave detection device 5. And the characteristic at the time of the grounding of the tire 6 is evaluated based on the result of a detection. For example, the reflected wave detection device 5 can image the reflected wave of the terahertz wave, and evaluate the characteristics of the tire 6 at the time of ground contact from the image.

（Ｓは滑り量、τはせん断力、添字ｘ、ｙは、ｘｙ平面におけるｘ方向、ｙ方向を表す）
τ_ｘ及びτ_ｙは、力センサ４により計測することができる。また、滑り量Ｓは、テラヘルツ波の反射波の検出結果に基づいて導出することができる。従って、本実施形態によれば、力センサ４により計測したせん断力τと導出した滑り量Ｓとにより、タイヤの摩耗エネルギーを算出してタイヤのトレッド摩耗速度Ｗを求めることができる。 Thus, according to the method of the present embodiment, the ground contact characteristics of the tire on the flat plate 2 can be evaluated even when the flat plate 2 has predetermined irregularities. For example, in this embodiment, if the shear force τ on the ground contact surface is measured by the force sensor 4, the wear energy can be calculated as follows. That is, the wear speed W of the tire tread can be expressed as W = A × E by using the mechanical wear energy E and the proportional constant A representing the ease of wear of rubber. Here, E can be expressed by Equation 1 below.

(S is the amount of slip, τ is the shearing force, subscripts x and y are the x and y directions in the xy plane)
τ _x and τ _y can be measured by the force sensor 4. The slip amount S can be derived based on the detection result of the reflected wave of the terahertz wave. Therefore, according to this embodiment, the tire tread wear speed W can be obtained by calculating the tire wear energy from the shearing force τ measured by the force sensor 4 and the derived slip amount S.

  FIG. 2 is a diagram schematically showing a tire ground contact characteristic evaluation apparatus used in another example of the method for evaluating tire ground contact characteristics on a flat plate having predetermined unevenness according to an embodiment of the present invention. In the example shown in FIG. 2, only the unevenness | corrugation aspect of the upper surface of the flat plate 2 differs from the example shown in FIG. The aspect of the unevenness on the lower surface of the flat plate 2 is the same as in FIG. That is, in the example shown in FIG. 2, large irregularities are formed on the upper surface of the flat plate 2. In the example shown in FIG. 2, the upper surface of the flat plate 2 has a rectangular wave cross-sectional shape, and the length of the upper side of the rectangular wave is 10 mm and the length of the lower side is 10 mm. Further, minute irregularities are formed in the rectangular wave cross-sectional shape. Specifically, the arithmetic average roughness Ra with a reference length of 8 mm is 10 to 80 μm, and the reference length is 2.5 mm. The arithmetic average roughness Ra is 2 to 10 μm. Also in the example shown in FIG. 2, the wavelength of the terahertz wave is larger than Ra with the reference length of 8 mm or Ra with the reference length of 2.5 mm. According to this, depending on the large unevenness (rectangular wave cross-sectional shape), since the unevenness is sufficiently large, the terahertz wave is not scattered, and the minute unevenness within the large unevenness (Ra having a reference length of 8 mm is 10 to 10 mm). As for the unevenness of 80 μm and the reference length of 2.5 mm and Ra of 2 to 10 μm, since the wavelength of the terahertz wave is larger than the Ra, the terahertz wave is not scattered by the minute unevenness. The lower surface is the same as the example shown in FIG. Therefore, also in the case of the example shown in FIG. 2, the same operation effect as the example shown in FIG. 1 can be exhibited. That is, for example, even when a large unevenness for evaluating vibration characteristics is formed on any surface (upper surface in FIG. 2) of the flat plate 2, the microscopic viewpoint with a reference length of 8 mm is eventually obtained. If the wavelength of the terahertz wave is larger than the arithmetic average roughness Ra, the terahertz wave is not scattered by the flat plate 2.

  FIG. 3 is a diagram schematically showing a tire ground contact characteristic evaluation device used in another example of the tire ground contact characteristic evaluation method on a flat plate having predetermined unevenness according to an embodiment of the present invention. In the example shown in FIG. 3, only the unevenness | corrugation aspect of the upper surface of the flat plate 2 differs from the example shown in FIG. The aspect of the unevenness on the lower surface of the flat plate 2 is the same as in FIG. That is, in the example shown in FIG. 3, the upper surface of the flat plate 2 is similar to the lower surface in the arithmetic average Ra (10 to 80 μm) with a reference length of 8 mm and the arithmetic average Ra (2 to 10 μm) with a reference length of 2.5 mm. )have. Also in the example shown in FIG. 3, the wavelength of the terahertz wave is larger than the Ra with the reference length of 8 mm or the Ra with the reference length of 2.5 mm on the upper surface and the lower surface. Also in this example, since the terahertz waves are not scattered on the upper surface and the lower surface as in the lower surface of FIG. 1, the same operational effects as the example shown in FIG. 1 can be achieved. Therefore, the present invention can also be used to evaluate the ground contact characteristics of a tire on a flat road surface.

  In the example shown in FIG. 1, unevenness that simulates an actual road surface is formed only on the upper surface of the flat plate 2. However, for example, unevenness with the same roughness may be formed only on the lower surface of the flat plate 2. The unevenness having the same roughness may be formed on the upper and lower surfaces of the flat plate 2. In short, the actual road surface is various as described above, such as paved roads (asphalt, concrete, etc.) and non-paved roads (stone, sand, earth, etc.). 2 is prepared, and the wavelength of the terahertz wave is selected so that the wavelength of the terahertz wave is larger than the Ra having the reference length of 8 mm or the reference length of 2.5 mm. The effect of the present invention can be obtained without being scattered by the flat plate 2. Then, in the path from the irradiation of the terahertz wave to the detection of the reflected wave, the terahertz wave should not be scattered by the flat plate 2. Therefore, the portion where the wavelength of the terahertz wave is larger than the Ra is at least a part of the upper surface and the lower surface. It will be sufficient if it is at least partly. On the other hand, from the viewpoint of evaluating the ground contact characteristics at the time of rolling of the tire, a portion where the wavelength of the terahertz wave is larger than the Ra can be the entire upper surface and lower surface. In addition, when both the irradiation apparatus 3 and the reflected wave detection apparatus 5 are arrange | positioned inside the flat plate 2, if the location where the wavelength of a terahertz wave is larger than said Ra exists in at least one part of any one surface, It will be good.

  Here, in the present invention, it is preferable to detect the reflected wave of the terahertz wave on the surface. FIG. 4 is an example of an image showing the movement of an identification point (indicated by a black circle in FIG. 4) that is a point to which a substance is attached. As shown in FIG. 4, when measuring a reflected wave on a surface, the movement of a point can be easily measured. On the other hand, for example, when the identification point moves, the reflected wave of the terahertz wave can be detected by a line. Further, by following the movement of the identification point, the reflected wave of the terahertz wave can be detected by the point.

  Further, in the present invention, a material having a terahertz wave absorption rate or reflectance larger or smaller than that of rubber is attached to the rubber surface as a tire contact surface, and the intensity of the detected terahertz wave is increased compared to the surroundings. Alternatively, it preferably includes detecting the position of the substance by detecting the decreased position. Specifically, when the absorption rate of the terahertz wave of the substance is larger than that of rubber, the position of the substance is detected by detecting the position where the intensity of the detected terahertz wave is reduced compared to the surroundings. When the absorption rate of the terahertz wave is smaller than that of rubber, the position of the substance is detected by detecting the position where the intensity of the detected terahertz wave is increased compared to the surroundings. In addition, when the reflectance of the terahertz wave of the substance is larger than that of rubber, the position of the substance is detected by detecting the position where the intensity of the detected terahertz wave increases compared to the surroundings, and the terahertz wave of the substance When the reflectance of the material is smaller than that of rubber, the position of the substance is detected by detecting the position where the intensity of the detected terahertz wave is reduced compared to the surroundings. The terahertz wave is reflected after a part of the terahertz wave enters the tire interior, not the tire surface. For this reason, it may be difficult to distinguish whether the reflected wave is a reflected wave from the tire surface or a reflection from the inside of the tire. On the other hand, in the above method, the movement of the tread surface can be measured more accurately by easily identifying the position of the substance. For example, a conductor can be used as the above substance. This is because the terahertz wave is absorbed by the conductor. More specifically, the substances include markings and paints containing metals such as titanium oxide and aluminum, seals made of metal or containing metal powder, and stickers that can be pasted, rubber containing a lot of conductive carbon black or carbon materials, etc. Various things can be used.

  Furthermore, in the present invention, an image showing a position where the intensity of the detected terahertz wave is increased or decreased as compared with the surroundings is acquired, and a distribution of positions of the substance in the ground plane is derived from the acquired image. Is preferred. Since the resolution of the measurement point is about the wavelength, the resolution of the measurement point in the present invention is about the wavelength of the terahertz wave (for example, the resolution is about 0.5 mm when the wavelength of the terahertz wave is 0.5 mm). Therefore, the movement of the identification point can be measured with higher accuracy by deriving the position distribution as much as possible with such resolution and taking it into consideration.

  In the present invention, the position distribution may include at least one of the center-of-gravity position obtained from the area, the centroid position obtained from the area, and the distribution range weighted by the intensity of the reflected wave from the substance. preferable. FIG. 5 is an example of an image showing the movement of the identification point, which is a point to which a substance is attached, and the distribution of the position of the identification point. The upper left figure and upper right figure in FIG. 5 illustrate the movement of the identification points (shown by hatching) when an identification point having a diameter of 1 mm is arranged on the tread surface and observed at a spatial resolution of 0.5 mm. ing. Therefore, in FIG. 5, the size of one cell is 0.5 mm × 0.5 mm. In the upper left diagram of FIG. 5, the identification points are distributed across the four cells. From there, the identification points move in the upper right direction in the figure, and in the upper right diagram of FIG. 5, the identification points are distributed across nine cells. Thus, first, the distribution range where the identification points are located can be determined from the acquired image. At this time, in the acquired image, all of the cells in which the area occupied by the identification points with respect to the cells is larger than 0 can be set as the distribution range of the substance, while the area occupied by the identification points with respect to the cells is a constant value. In the following cases, it can be considered that the substance is not distributed. In the case shown in the upper diagram of FIG. 5, the center of gravity position and the centroid position can be obtained from the area weighted by the intensity of the reflected wave from the substance. For example, in the upper right diagram of FIG. A large cell can be used as the position of the center of gravity and the position of the centroid. The lower diagram of FIG. 5 is a diagram in which the gravity center position, the centroid position, and the distribution range corresponding to the upper diagram of FIG. In the lower diagram of FIG. 5, the entire cell is displayed with a predetermined shading for one cell, and the shading is determined by the size of the area occupied by the identification point with respect to the cell. In this example, when the area occupied by the identification points with respect to the grid is below a certain level, it is considered that the area is not distributed. The area of the area where the area occupied by the identification point relative to the area of the area is relatively smaller than that of the area (the shaded area in the figure). In this way, the position of the center of gravity, the position of the centroid, and the distribution range can be grasped more visually based on, for example, shading on the image. In this case, it is possible to more visually grasp the portion that is shown most darkly on the image as the grid of the center of gravity position and the centroid position. In addition, as shown in the upper right diagram and the lower right diagram in FIG. 5, when the area occupied by the identification points with respect to the squares is almost the same, the squares can be visualized more as the same darkness. In this case, the center of gravity position, the centroid position, and the distribution range can be grasped more visually. In this case, for example, the center of gravity position and the centroid position when four cells are regarded as one cell can be obtained. Thus, by obtaining at least one of the center of gravity position, the centroid position, and the distribution range, the movement of the identification point can be measured with good accuracy. At that time, as shown in the lower diagram of FIG. 5, the movement of the identification point can be grasped more visually by performing the visualization process by shading.

  A tire having a tire size PSR195 / 65R15 and having no tread pattern was manufactured as a prototype. When using a device as shown in Fig. 1 and incorporating the tire into the applicable rim, setting the internal pressure to 210 kPa, applying a load of 4.41 kN, and rolling on the transparent acrylic plate at a speed of 1 km / h and a slip angle of 1 ° The amount of slip on the tire tread surface was measured. In this example, the tire was stationary so as to be rotatable, and the transparent acrylic plate was moved at a speed of 1 km / h by a moving device.

  As Comparative Example 1, a transparent acrylic plate having a flat surface (upper and lower surfaces) (Ra = 1 μm at a reference length of 8 mm) was used, and the reflected light was measured with a video camera by irradiating visible light. As Comparative Example 2, a transparent acrylic plate having Ra = 40 μm with a reference length of 8 mm on the upper surface (the lower surface is flat) was used and measured with a video camera by irradiating visible light. As Invention Example 1, a transparent acrylic plate having a reference length of 8 mm and Ra = 40 μm on the upper surface (the lower surface is flat) was used, and a 1 THz terahertz wave (wavelength: 0.3 mm) was irradiated to detect the surface. . As invention example 2, a transparent acrylic plate having a reference length of 8 mm and Ra = 40 μm on the upper surface (the lower surface is flat) is used, and a THz wave of 0.5 THz (wavelength 0.6 mm) is irradiated to detect the surface. went. Here, in Invention Examples 1 and 2, marking was performed with a marking pen containing titanium oxide on the tire surface. In Invention Examples 1 and 2, the amount of slip was evaluated by acquiring images of marked identification points. Here, since the terahertz wave is absorbed by titanium oxide, an area where the reflection intensity is lower than the surroundings is measured as an identification point. Inventive example 1 is the center of gravity position obtained from the area weighted by the intensity of the reflected wave, and in inventive example 2, the centroid position obtained from the area is obtained as the slip amount.

  As shown in Table 1, in Comparative Example 2, it was impossible to measure the amount of slip when kicking out a tire on a transparent acrylic plate having a reference length of 8 mm and Ra = 20 μm on the upper surface. According to Invention Examples 1 and 2, it was found that the amount of slip when kicking a tire on a transparent acrylic plate having an unevenness of Ra = 40 μm with a reference length of 8 mm on the upper surface could be measured.

1: tire contact characteristic evaluation device, 2: flat plate, 3: irradiation device, 4: force sensor,
5: Reflected wave detection device, 6: Tire

Claims (6)

Place the tire on one side of the flat plate,
A predetermined load is applied to the tire, or no load is applied,
The tire is irradiated with a terahertz wave having a frequency of 0.1 THz to 10 THz from the other surface side of the flat plate or from the inside of the flat plate, and the wavelength of the terahertz wave is at least one of the one surface of the flat plate. The roughness of the part is larger than the average height,
Detecting a reflected wave of the terahertz wave from the tire;
A method for evaluating tire ground contact characteristics, wherein characteristics of the tire at the time of ground contact are evaluated based on a result of the detection. Place the tire on one side of the flat plate,
A predetermined load is applied to the tire, or no load is applied,
The tire is irradiated with a terahertz wave having a frequency of 0.1 THz to 10 THz from the other surface side of the flat plate or from the inside of the flat plate, and the wavelength of the terahertz wave is at least one of the one surface of the flat plate. Greater than the arithmetic average roughness Ra defined by JIS B0601 with a reference length of 8 mm, or greater than the arithmetic average roughness Ra defined by JIS B0601 with a reference length of 2.5 mm ,
Detecting a reflected wave of the terahertz wave from the tire;
The tire contact property evaluation method according to claim 1, wherein the contact property of the tire is evaluated based on the detection result.   The method for evaluating tire ground contact characteristics according to claim 1, wherein a reflected wave of the terahertz wave is detected by a surface. Attaching a substance having an absorption rate or reflectance of the terahertz wave larger or smaller than that of the rubber to the surface of the rubber to be a ground contact surface of the tire,
The tire according to any one of claims 1 to 3, comprising detecting the position of the substance by detecting a position where the intensity of the detected terahertz wave is increased or decreased compared to the surroundings. Evaluation method for grounding characteristics. Obtaining an image showing a position where the intensity of the detected terahertz wave is increased or decreased compared to the surroundings;
The tire ground contact characteristic evaluation method according to claim 4, wherein the distribution of the position of the substance in the ground contact surface is derived from the acquired image.   The distribution of the position includes at least one of a center-of-gravity position obtained from an area, a centroid position obtained from the area, and a distribution range weighted by the intensity of a reflected wave from the substance. The evaluation method of the tire ground contact characteristic as described.

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