JP6815842B2 - Tire contact condition measurement method - Google Patents

Description

The present invention relates to a method for measuring the ground contact state of a tire on a wet road surface.

Conventionally, as a method of measuring the ground contact state of a tire, a method of grounding the tire on a flat plate and photographing the ground contact shape at that time has been used. Specifically, a liquid layer made of white liquid is provided on the surface. A method of grounding a tire on a transparent plate to photograph the ground contact shape of the tire (Patent Document 1), a photoexcitation fluorescence method, a light interference method, a total reflection method, and the like are known.

Further, since the tire characteristics when the tire is pressed onto the flat plate and the tire characteristics on the actual road surface are dissociated, in Patent Document 2, the tire is grounded on a ground contact surface having irregularities equivalent to the actual road surface. A method of photographing the ground contact shape of the tire has been proposed. However, it has been difficult to apply the optical interferometry method or the total reflection method to the method of measuring the ground contact state of the tire on a wet road surface.

Therefore, in Non-Patent Document 1, a photoexcited fluorescence method is adopted as a method for measuring the ground contact state of a tire on a wet road surface, and when excitation light having a wavelength of 525 to 550 nm is irradiated as a fluorescent agent, fluorescence having a wavelength of about 580 nm is emitted. It has been proposed to use Rhodamine B.

Japanese Unexamined Patent Publication No. 2012-154858 Japanese Unexamined Patent Publication No. 2003-240681 Japanese Unexamined Patent Publication No. 2001-141434

Masao Eguchi, "Rubber Plate Using Photo-Induced Fluorescence Method-Analysis of Indirect Contact on Concavo-convex Surface-Visualization and Luminance Histogram Analysis-", Tribologist Vol. 58, No. 10 (2013), pp. 763-772

However, since the difference in peak wavelength between the excitation spectrum and the fluorescence spectrum of Rhodamine B used in Non-Patent Document 1 is only about 30 to 55 nm, it is difficult to sufficiently separate the excitation spectrum and the fluorescence spectrum, and measurement is performed. There was room for improvement in accuracy.

In view of the above points, it is an object of the present invention to provide a method for more accurately measuring the ground contact state of a tire on a wet road surface.

In addition, Patent Document 3 discloses a method of measuring the contact state between an elastic sealing product typified by rubber and an object to be sealed by the sealing surface of the sealing product, but the ground contact state of the tire is described. It is not intended to be measured, nor is it intended to use the photoinduced fluorescence method.

In the tire ground contact state measuring method according to the present invention, a fluorescent liquid is interposed between a transparent plate provided with a ground contact surface having irregularities equivalent to an actual road surface on one surface and the tire, and the tire is grounded on the ground contact surface. The process and the process of irradiating the fluorescent liquid interposed between the ground surface and the tire with excitation light from the side opposite to the ground surface of the transparent plate and measuring the brightness distribution of the fluorescence emitted from the fluorescent liquid. The method is such that the fluorescent liquid contains pyranine as a hydrophilic fluorescent dye having a peak wavelength difference between the excitation spectrum and the fluorescent spectrum of 100 nm or more, and the pH of the fluorescent liquid is 5 to 8 .

The tire ground contact state measuring method may further include a step of converting the measured luminance distribution of fluorescence into the film thickness distribution of the fluorescence liquid.

The tire ground contact state measuring method can further include a step of performing binarization with an arbitrary film thickness as a threshold value based on the obtained film thickness distribution.

According to the measuring method of the present invention, it is possible to accurately measure the ground contact state of a tire on a wet road surface.

The simplified figure which shows the structure of the apparatus which performs the tire contact state measurement method which concerns on one Embodiment. The figure which shows simplified the relationship between the excitation spectrum and the fluorescence spectrum when rhodamine B is used as a fluorescent dye. The figure which shows simplified the relationship between the excitation spectrum and the fluorescence spectrum when pyranine is used as a fluorescent dye.

Hereinafter, the tire ground contact state measuring method of one embodiment according to the present invention will be described with reference to FIGS. 1 to 3.

In the tire ground contact state measuring method of the present embodiment, a fluorescent liquid is interposed between a transparent plate provided with a ground contact surface having irregularities equivalent to an actual road surface on one surface and the tire, and the tire is grounded on the ground contact surface. The process and the process of irradiating the fluorescent liquid interposed between the ground surface and the tire with excitation light from the side opposite to the ground surface of the transparent plate and measuring the brightness distribution of the fluorescence emitted from the fluorescent liquid. It is assumed that the fluorescent liquid contains a hydrophilic fluorescent dye having a peak wavelength difference between the excitation spectrum and the fluorescence spectrum of 100 nm or more.

FIG. 1 is a simplified diagram showing a configuration of an apparatus for performing the tire ground contact state measuring method of the present embodiment. As shown in FIG. 1, a transparent plate 1 having a ground contact surface having irregularities equivalent to an actual road surface on one surface is installed on the transparent plate installation base 9, and a tire 10 is placed on the ground contact surface of the transparent plate 1. It is grounded. A fluorescent liquid 2 is interposed between the ground contact surface and the tire 10. Below the transparent plate installation table 9, there are a light source 3, a filter 7 that transmits and separates only light of a specific wavelength from the light emitted from the light source 3, and a dichroic mirror 5 that reflects only light of a specific wavelength. , A mirror 6 that reflects the fluorescence emitted from the fluorescent liquid 2, a filter 8 that transmits and separates only light of a specific wavelength from the emitted fluorescence, and a photographing means 4 that measures the fluorescence transmitted through the filter 8. It is arranged.

The tire ground contact state measuring method of the present embodiment can be carried out as follows by using, for example, pyranine as a hydrophilic fluorescent dye and using the above device. That is, the excitation light is irradiated using the ultraviolet LED (peak wavelength 365 nm) as the light source 3, and the excitation light having a wavelength of 400 nm or less is separated by the filter 7 (400 nm low-pass filter). The separated excitation light is reflected by the dichroic mirror 5, and the excitation light is applied to the fluorescent liquid 2 interposed between the tire 10 and the ground surface from the side opposite to the ground surface of the transparent plate 1. The pyranine contained in the fluorescent solution 2 is transitioned from the ground state to the excited state. The excited state of pyranine then returns to the ground state, at which time fluorescence is emitted. The emitted fluorescence is transmitted through the dichroic mirror 5 and then reflected by the mirror 6, and the fluorescence having a wavelength of 480 nm or more is separated by the filter 8 (480 nm high-pass filter). A luminance distribution (fluorescence intensity image) can be obtained by photographing the separated fluorescence with the photographing means 4.

The tire ground contact state measuring method of the present embodiment may further include a step of converting the luminance distribution obtained by the above measuring method into the film thickness distribution of the fluorescent liquid. When the film thickness of the fluorescent liquid 2 between the tire 10 and the contact patch is thin, the brightness is proportional to the film thickness. Therefore, by converting the quantified brightness into the film thickness, the obtained brightness distribution is converted to the film thickness distribution. It is possible to convert to. Further, the brightness and the film thickness may be calibrated as a preliminary step of this step. For example, a calibration curve of film thickness and brightness can be obtained using a glass plate having known dimensions, and the brightness can be converted into film thickness by applying the calibration curve. As a result, it can be applied even when the brightness and the film thickness are not in a proportional relationship.

Further, the tire ground contact state measuring method of the present embodiment may further include a step of performing binarization with an arbitrary film thickness as a threshold value based on the obtained film thickness distribution. Specifically, by setting a specific film thickness as a threshold value, a region where the film thickness is equal to or less than the threshold value is defined as a region where the tire 10 and the contact patch are in contact with each other. The area in contact with the tires can be calculated.

The fluorescent solution 2 is an aqueous solution containing a hydrophilic fluorescent dye having a peak wavelength difference of 100 nm or more between the excitation spectrum and the fluorescence spectrum. The hydrophilic fluorescent dye is not particularly limited as long as the difference in peak wavelength between the excitation spectrum and the fluorescence spectrum is 100 nm or more. For example, pyranine, DY-481XL-Carboxylic Acid manufactured by Dynamics, DY-521XL-Carboxylic Acid, ATTO 490LS carboxy manufactured by ATTO-TEC, etc. can be used, and pyranine can be preferably used from the viewpoint of safety and cost. Further, in the case of a hydrophilic fluorescent dye having a plurality of peak wavelengths of the excitation spectrum and / or the fluorescence spectrum, the peak wavelengths of the excitation spectrum and the fluorescence spectrum can be set by using a filter or the like for the excitation spectrum and / or the fluorescence spectrum. The peak wavelength may be selected and used so that the difference is 100 nm or more.

Pyranine is a hydrophilic pH-sensitive fluorescent dye, and when the pH is neutral to acidic, the peak wavelength of the excitation spectrum appears at around 365 nm and 400 nm, and when the pH is alkaline, the peak wavelength of the excitation spectrum appears at around 450 nm. .. Further, the peak wavelength of the fluorescence spectrum is mainly around 510 nm regardless of the pH, and the fluorescence spectrum of 400 nm or less is hardly detected. Therefore, when pyranine is used as the hydrophilic fluorescent dye, the pH of the fluorescent liquid 2 is preferably neutral to acidic from the viewpoint that the difference in peak wavelength between the excitation spectrum and the fluorescence spectrum is 100 nm or more. Is more preferably 5-8. Further, in the present embodiment, since the filter 7 that transmits only the wavelength of 400 nm or less is used for the excitation light, the peak wavelength of the excitation spectrum of pyranine is mainly 365 nm, and the peak of the excitation spectrum and the fluorescence spectrum. The maximum wavelength difference is 145 nm.

As shown in FIG. 2, when Rhodamine B used in Non-Patent Document 1 is used, the difference in peak wavelength between the excitation spectrum and the fluorescence spectrum is only about 40 nm, and the wavelength range between the excitation spectrum and the fluorescence spectrum is large. It is difficult to separate the excitation spectrum and the fluorescence spectrum because they partially overlap. On the other hand, as shown in FIG. 3, in the present embodiment, the excitation spectrum and the fluorescence spectrum are obtained by using a fluorescent dye having a peak wavelength difference of 100 nm or more between the excitation spectrum and the fluorescence spectrum as the fluorescent solution. Since the excitation spectrum and the fluorescence spectrum can be sufficiently separated from each other with almost no overlap in the wavelength range with the above, the measurement accuracy can be improved.

The concentration of the hydrophilic fluorescent dye in the fluorescent solution is not particularly limited, but when pyranine is used, it is preferably 100 to 10000 mg / L.

The method for producing a transparent plate having a ground contact surface having irregularities equivalent to the actual road surface is not particularly limited. For example, asphalt corresponding to the actual road surface is molded with silicone rubber, a transparent resin is poured into this mold, and a vacuum is applied. It can be produced by curing in a degassed state. Examples of the transparent resin include urethane-based resins.

The light source 3 can be appropriately selected and used according to the excitation spectrum of the hydrophilic fluorescent dye to be used, and is not particularly limited, but has a peak wavelength near the peak wavelength of the excitation spectrum of the hydrophilic fluorescent dye to be used. It is preferable that the light source has a single wavelength, and more preferably a single wavelength. When the hydrophilic fluorescent dye used is pyranine, the peak wavelength of the irradiated light is preferably 350 to 400 nm. The intensity of the excitation light to be irradiated is not particularly limited, but for example, when calibrating the brightness and the film thickness described above, the intensity at which the thickness and brightness calibration curve according to the purpose can be obtained may be examined. Good.

The dichroic mirror 5 and the filters 7 and 8 are not particularly limited, and can be appropriately selected and used according to the excitation spectrum and the fluorescence spectrum of the hydrophilic fluorescent dye to be used. The filters 7 and 8 include, for example, a wavelength selection type fluorescence filter that removes noise when performing fluorescence detection, and a high-pass filter that cuts light on the wavelength side shorter than the specified wavelength and transmits light on the long wavelength side. (Long pass filter), low pass filter that cuts light on the longer wavelength side than the specified wavelength and transmits light on the short wavelength side (short pass filter), transmits only light in a certain wavelength range, and other short wavelength sides And a band pass filter that cuts light on the long wavelength side.

Although embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

The tire ground contact state measuring method of the present invention can be used for measuring the ground contact state of various tires of passenger cars, light trucks, buses and the like.

1 ... Transparent plate 2 ... Fluorescent liquid 3 ... Light source 4 ... Photographing means 5 ... Dichroic mirror 6 ... Mirror 7 ... Filter 8 ... Filter 9 ... Transparent plate Installation stand 10 ... Tires

Claims (3)

A process in which a fluorescent liquid is interposed between a transparent plate provided with a ground contact surface having irregularities equivalent to an actual road surface on one surface and a tire to ground the tire on the ground contact surface.
From the side opposite to the ground plane of the transparent plate, the fluorescent liquid interposed between the ground plane and the tire is irradiated with excitation light, and the brightness distribution of the fluorescence emitted from the fluorescent liquid is measured. ,
The fluorescent solution contains pyranine as a hydrophilic fluorescent dye having a peak wavelength difference of 100 nm or more between the excitation spectrum and the fluorescence spectrum .
A method for measuring a tire ground contact state, wherein the pH of the fluorescent solution is 5 to 8 . The tire ground contact state measuring method according to claim 1, further comprising a step of converting the measured luminance distribution of fluorescence into a film thickness distribution of a fluorescent liquid. The tire ground contact state measuring method according to claim 2 , further comprising a step of performing binarization with an arbitrary film thickness as a threshold value based on the obtained film thickness distribution.