JP2017058244A - Rubber friction test method - Google Patents

Rubber friction test method Download PDF

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JP2017058244A
JP2017058244A JP2015183002A JP2015183002A JP2017058244A JP 2017058244 A JP2017058244 A JP 2017058244A JP 2015183002 A JP2015183002 A JP 2015183002A JP 2015183002 A JP2015183002 A JP 2015183002A JP 2017058244 A JP2017058244 A JP 2017058244A
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rubber
test piece
road surface
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rubber test
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JP6594715B2 (en
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幸司 荒川
Koji Arakawa
幸司 荒川
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Toyo Tire Corp
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Toyo Tire and Rubber Co Ltd
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Abstract

PROBLEM TO BE SOLVED: To provide a rubber friction test method capable of accurately measuring the friction coefficient between a test road surface and a rubber test piece.SOLUTION: The flat surface of a rubber test piece 2 is pressed on a test road surface 1 that includes an aggregate 90 and simulates an actual road surface, the load when the rubber test piece 2 is rectilinearly moved while being slid on the flat test road surface 1 is measured, and the friction coefficient between the test road surface 1 and the rubber test piece 2 is measured. Thus, the variation in the contact area can be made small and stable, and the ununiformity of the contact pressure can be suppressed. Furthermore, the occurrence of the speed difference in the contact plane is suppressed, and the friction coefficient between the test road surface 1 and the rubber test piece 2 can be accurately measured.SELECTED DRAWING: Figure 1

Description

本発明は、実路面を模擬してなる試験路面とゴム試験片との間の摩擦係数を測定するためのゴム摩擦試験方法に関する。   The present invention relates to a rubber friction test method for measuring a friction coefficient between a test road surface simulating an actual road surface and a rubber test piece.

従来、屋内に設置された試験路面とゴム試験片を用いて、自動車用タイヤに採用するゴム材料の摩擦特性を評価する試験が行われている。このような試験において、試験路面とゴム試験片との間の摩擦係数を精度良く測定するには、試験路面の性状を実路面に近付けることが重要であるが、それに加え、試験路面上でのゴム試験片の接地面積の変化を抑えながら、そのゴム試験片の接地圧の均一化を図ることも重要である。   2. Description of the Related Art Conventionally, a test for evaluating the friction characteristics of a rubber material used for an automobile tire has been performed using a test road surface and a rubber test piece installed indoors. In such tests, in order to accurately measure the coefficient of friction between the test road surface and the rubber specimen, it is important to bring the properties of the test road surface closer to the actual road surface. It is also important to equalize the contact pressure of the rubber test piece while suppressing the change in the contact area of the rubber test piece.

特許文献１には、実路面を模擬してなる試験路面をドラムに形成し、その上で転動させたタイヤの摩耗形態を観察する試験が開示されている。しかし、タイヤの踏面は外周側に突出した湾曲面であるため、ゴム硬度などの物性に応じて接地面積が変化しやすい。しかも、最も突出した部位で接地圧が相対的に高くなるので、接地圧が不均一になる。また、曲率を有するドラムに試験路面が形成されることも、接地圧の不均一化の原因になりうる。これらの理由から、かかる手法は摩擦係数の測定には適していない。   Patent Document 1 discloses a test in which a test road surface simulating an actual road surface is formed on a drum, and a wear form of a tire rolled on the test road surface is observed. However, since the tread surface of the tire is a curved surface protruding to the outer peripheral side, the contact area is likely to change according to physical properties such as rubber hardness. In addition, since the ground pressure is relatively high at the most protruding portion, the ground pressure becomes non-uniform. Further, the formation of a test road surface on a drum having a curvature can also cause unevenness in the contact pressure. For these reasons, such a technique is not suitable for measuring the coefficient of friction.

特許文献２には、粉砕石などで形成される円板状の試験路面の外周面に、円板状のゴム試験片の外周面を押し当て、それらを相互独立に回転させて摩擦速度を測定するランボーン摩耗試験機が記載されている。しかし、試験路面とゴム試験片とが湾曲面同士を接触させて接地圧が不均一になりやすいため、この手法も摩擦係数の測定には適していない。特許文献１，２に記載の従来方法は、所定の荷重条件下での摩擦特性の評価に用いられるものであり、所定の圧力条件下での摩擦係数の測定には不向きと考えられる。   In Patent Document 2, the outer peripheral surface of a disk-shaped rubber test piece is pressed against the outer peripheral surface of a disk-shaped test road surface formed of crushed stone, and the friction speed is measured by rotating them independently of each other. A lamborn wear tester is described. However, this method is also not suitable for measuring the friction coefficient because the test road surface and the rubber test piece tend to bring the curved surfaces into contact with each other and the contact pressure tends to be uneven. The conventional methods described in Patent Documents 1 and 2 are used for evaluation of friction characteristics under a predetermined load condition, and are considered unsuitable for measuring a friction coefficient under a predetermined pressure condition.

ターンテーブルの回転面に試験路面を形成し、その上でゴム試験片を転動または摺動させる手法もまた、摩擦係数の測定には不向きである。この場合、ゴム試験片は、ターンテーブルの周方向に沿った環状経路を通って、試験路面上を旋回移動（カーブ）することになる。それ故、ゴム試験片の接地面のうちターンテーブルの回転中心から近い領域では、回転中心から遠い領域に比べて、移動速度が相対的に大きくなり、そのような速度差の発生によって正確な測定が困難になる。   A method of forming a test road surface on the rotating surface of the turntable and rolling or sliding the rubber test piece thereon is also unsuitable for measuring the friction coefficient. In this case, the rubber test piece turns (curves) on the test road surface through an annular path along the circumferential direction of the turntable. Therefore, in the area close to the rotation center of the turntable on the ground contact surface of the rubber test piece, the moving speed is relatively larger than that in the area far from the rotation center. Becomes difficult.

特開平７−２００３０号公報JP-A-7-20030 特開２０１０−２１０３９７号公報JP 2010-210397 A

本発明は上記実情に鑑みてなされたものであり、その目的は、試験路面とゴム試験片との間の摩擦係数を精度良く測定できるゴム摩擦試験方法を提供することにある。   The present invention has been made in view of the above circumstances, and an object thereof is to provide a rubber friction test method capable of accurately measuring a friction coefficient between a test road surface and a rubber test piece.

上記目的は、下記の如き本発明により達成することができる。即ち、本発明に係るゴム摩擦試験方法は、骨材を含んで実路面を模擬してなる試験路面にゴム試験片の平坦面を押し当て、平坦な前記試験路面上で前記ゴム試験片をすべらせながら直進移動させたときの荷重を計測し、前記試験路面と前記ゴム試験片との間の摩擦係数を測定するものである。   The above object can be achieved by the present invention as described below. That is, in the rubber friction test method according to the present invention, a flat surface of a rubber test piece is pressed against a test road surface including an aggregate to simulate an actual road surface, and the rubber test piece is slipped on the flat test road surface. The load is measured when moving straight, while the friction coefficient between the test road surface and the rubber test piece is measured.

この方法では、骨材を含んで実路面を模擬してなる試験路面が用いられ、その平坦な試験路面にゴム試験片の平坦面が押し当てられる。このため、接地面積の変化が小さく安定するとともに、接地圧の不均一化を抑制できる。しかも、試験路面上でゴム試験片をすべらせながら直進移動させるので、接地面内での速度差の発生が抑えられる。したがって、この方法によれば、試験路面とゴム試験片との間の摩擦係数を精度良く測定することができる。   In this method, a test road surface including an aggregate and simulating an actual road surface is used, and the flat surface of the rubber test piece is pressed against the flat test road surface. For this reason, the change in the contact area is small and stable, and the uneven contact pressure can be suppressed. In addition, since the rubber test piece is moved straight while sliding on the test road surface, the occurrence of a speed difference in the ground contact surface can be suppressed. Therefore, according to this method, the friction coefficient between the test road surface and the rubber test piece can be accurately measured.

前記ゴム試験片の前方側エッジ部の側面と前記平坦面とが鈍角をなすことが好ましい。この場合、前記ゴム試験片の前方側エッジ部の側面が傾斜面または湾曲面により形成されているものが例示される。前方側エッジ部の側面と平坦面とが鈍角をなすことにより、ゴム試験片をすべらせながら直進移動させた際に、前方側エッジ部が試験路面に引っ掛かりにくくなり、その結果、すべり状態における接地面積の低下や接地圧の不均一化が抑制される。これに対して、例えばゴム試験片が完全な直方体形状をなす場合には、直角に形成された前方側エッジ部が試験路面に引っ掛かって測定が不安定になりやすい。   It is preferable that the side surface of the front edge portion of the rubber test piece and the flat surface form an obtuse angle. In this case, an example in which the side surface of the front edge portion of the rubber test piece is formed by an inclined surface or a curved surface is exemplified. The obtuse angle between the side surface of the front edge and the flat surface makes it difficult for the front edge to get caught on the test road surface when the rubber test piece is moved straight while sliding. A reduction in area and non-uniform contact pressure are suppressed. On the other hand, for example, when the rubber test piece has a complete rectangular parallelepiped shape, the front edge formed at a right angle is caught on the test road surface, and the measurement tends to become unstable.

濡れた路面での摩擦係数を測定する場合には、前記試験路面上に水膜を形成し、濡れた前記試験路面と前記ゴム試験片との間の摩擦係数を測定する。その際、前記ゴム試験片の前方側エッジ部の側面の高さを前記水膜の厚みよりも大きくすることが好ましい。これにより、高速すべり条件における水膜の抵抗を減らし、測定精度を高めることができる。   When measuring the friction coefficient on the wet road surface, a water film is formed on the test road surface, and the friction coefficient between the wet test road surface and the rubber test piece is measured. In that case, it is preferable to make the height of the side surface of the front edge part of the rubber test piece larger than the thickness of the water film. Thereby, the resistance of the water film under high-speed sliding conditions can be reduced, and the measurement accuracy can be increased.

前記平坦面が、直径２０ｍｍの円形を内包した大きさを有することが好ましい。試験路面に用いられる骨材の大きさはせいぜい１５ｍｍ程度であるため、このような大きさを平坦面が有することにより、試験路面上を移動するゴム試験片の平坦面内（即ち、接地面内）に適度な数の骨材が含まれ、摩擦係数を精度良く測定できる。   The flat surface preferably has a size including a circle having a diameter of 20 mm. Since the size of the aggregate used for the test road surface is at most about 15 mm, the flat surface has such a size, so that the rubber test piece moving on the test road surface is within the flat surface (that is, within the ground contact surface). ) Contains an appropriate number of aggregates, and the coefficient of friction can be measured accurately.

ゴム摩擦試験機の一例を概略的に示す図Diagram showing an example of a rubber friction tester ゴム試験片の移動経路を説明する図Diagram explaining the movement path of rubber test piece 好ましい形状を有するゴム試験片の三面図Three views of a rubber specimen having a preferred shape ゴム試験片の前方側エッジ部の側面の例を示す図The figure which shows the example of the side of the front edge part of a rubber test piece ゴム試験片の別形状を示す三面図Three views showing different shapes of rubber test pieces 別実施形態の別形状を示す三面図Three views showing another shape of another embodiment 摩擦係数の測定結果を示すグラフGraph showing friction coefficient measurement results

以下、本発明の実施の形態について図面を参照しながら説明する。   Hereinafter, embodiments of the present invention will be described with reference to the drawings.

本実施形態では、図１に示したゴム摩擦試験機１０を用いて、試験路面１とゴム試験片２との間の摩擦係数を測定する例を示す。但し、本発明に係るゴム摩擦試験方法は、かかるゴム摩擦試験機を用いて実施されるものに限られない。このゴム摩擦試験機１０は、骨材９０を含んで実路面を模擬してなる試験路面１と、ゴム試験片２を保持するホルダー３と、試験路面１にゴム試験片２を押し当てる荷重装置４と、試験路面１に対してゴム試験片２を相対移動させるための駆動装置５と、ゴム試験片２に作用する荷重を計測する荷重センサ６と、試験に必要な動作の制御を行う制御装置７とを備える。   In the present embodiment, an example in which the friction coefficient between the test road surface 1 and the rubber test piece 2 is measured using the rubber friction tester 10 shown in FIG. However, the rubber friction test method according to the present invention is not limited to the one carried out using such a rubber friction tester. This rubber friction tester 10 includes a test road surface 1 that simulates an actual road surface including an aggregate 90, a holder 3 that holds a rubber test piece 2, and a load device that presses the rubber test piece 2 against the test road surface 1. 4, a driving device 5 for moving the rubber test piece 2 relative to the test road surface 1, a load sensor 6 for measuring a load acting on the rubber test piece 2, and a control for controlling operations necessary for the test. Device 7.

試験路面１は、アスファルト路面やコンクリート路面などの実路面を模擬してなる。試験路面１は、道路で実際に使用される骨材、またはそれと同等の性状を持つ硬質な骨材を接着剤で固着することにより形成される。或いは、試験路面１は、実際の道路から路面を切り出し、それを測定用に加工することにより形成される。試験路面１を形成する方法は、これら以外でもよく、特に限定されない。試験路面１の表面は、骨材９０による多少の凹凸はあるものの、全体として平坦に形成されている。   The test road surface 1 simulates an actual road surface such as an asphalt road surface or a concrete road surface. The test road surface 1 is formed by fixing an aggregate actually used on a road or a hard aggregate having properties equivalent to the aggregate with an adhesive. Alternatively, the test road surface 1 is formed by cutting out a road surface from an actual road and processing it for measurement. The method for forming the test road surface 1 may be other than these, and is not particularly limited. Although the surface of the test road surface 1 has some unevenness due to the aggregate 90, it is formed flat as a whole.

ゴム試験片２は、加硫ゴムにより作製され、試験路面１に押し当てられる平坦面を有する。図１の例では、ゴム試験片２が完全な直方体形状をなし、その上面が板状のホルダー３に接着されている。したがって、試験路面１と対面するゴム試験片２の下面が、試験路面１に押し当てられる平坦面となる。   The rubber test piece 2 is made of vulcanized rubber and has a flat surface that is pressed against the test road surface 1. In the example of FIG. 1, the rubber test piece 2 has a complete rectangular parallelepiped shape, and its upper surface is bonded to a plate-like holder 3. Therefore, the lower surface of the rubber test piece 2 facing the test road surface 1 becomes a flat surface pressed against the test road surface 1.

ホルダー３は荷重装置４に接続されている。荷重装置４は、試験路面１に対して垂直なＺ方向（図１の上下方向）に沿ってホルダー３を往復動可能に構成されている。このホルダー３の位置（ホルダー３と試験路面１との間隔）を適宜に設定することで、ゴム試験片２に入力されるＺ方向の荷重を調整でき、延いては所定の圧力条件下でゴム試験片２を試験路面１に押し当てることができる。荷重装置４は、サーボモータにより構成されているが、他のアクチュエータ機構を利用しても構わない。   The holder 3 is connected to a load device 4. The load device 4 is configured to reciprocate the holder 3 along a Z direction (vertical direction in FIG. 1) perpendicular to the test road surface 1. By appropriately setting the position of the holder 3 (the distance between the holder 3 and the test road surface 1), the load in the Z direction inputted to the rubber test piece 2 can be adjusted, and the rubber under a predetermined pressure condition. The test piece 2 can be pressed against the test road surface 1. Although the load device 4 is configured by a servo motor, other actuator mechanisms may be used.

駆動装置５は、荷重装置４を支持するテーブル８をＸ方向（図１の左右方向）に沿って往復動可能に構成されている。このテーブル８の移動によってホルダー３が移動し、試験路面１上でゴム試験片２をすべらせながら移動させることができる。アクチュエータ９は、Ｘ方向とＺ方向の両方に垂直なＹ方向（図１の紙面に垂直な方向）に沿ってテーブル８を往復動可能に構成されていて、Ｙ方向におけるゴム試験片２と試験路面１との位置合わせに利用される。本実施形態では、駆動装置５とアクチュエータ９が、それぞれサーボモータにより構成されているが、これに限定されない。   The drive device 5 is configured to be able to reciprocate along the X direction (left and right direction in FIG. 1) of the table 8 that supports the load device 4. The holder 3 is moved by the movement of the table 8, and the rubber test piece 2 can be moved while sliding on the test road surface 1. The actuator 9 is configured to be able to reciprocate the table 8 along a Y direction (a direction perpendicular to the paper surface of FIG. 1) perpendicular to both the X direction and the Z direction. Used for alignment with the road surface 1. In the present embodiment, the drive device 5 and the actuator 9 are each constituted by a servo motor, but the present invention is not limited to this.

荷重センサ６は、垂直成分及び水平二成分の計三成分の荷重を計測可能であり、ゴム試験片２に作用するＺ方向の荷重（垂直力）、Ｘ方向の荷重（前後力）及びＹ方向の荷重（横力）を計測することができる。荷重センサ６は、例えばロードセルによって構成される。本実施形態では、ホルダー３の上側（ゴム試験片２とは反対側）に荷重センサ６が取り付けられている。   The load sensor 6 can measure a total of three components, a vertical component and a horizontal two component, and a load in the Z direction (vertical force), a load in the X direction (front-rear force) and a Y direction acting on the rubber test piece 2. Load (lateral force) can be measured. The load sensor 6 is constituted by a load cell, for example. In the present embodiment, a load sensor 6 is attached to the upper side of the holder 3 (the side opposite to the rubber test piece 2).

制御装置７は、摩擦係数の測定に必要な計算を行う演算部７ａと、荷重装置４や駆動装置５などの作動を制御する作動制御部７ｂと、試験作業者からの入力を受け付ける入力部７ｃと、試験機１０の操作や設定などに関する各種情報を画面上に表示する表示部７ｄとを備える。荷重センサ６による計測値は制御装置７に送られ、それに基づいて演算部７ａが摩擦係数を計算する。   The control device 7 includes a calculation unit 7a that performs calculations necessary for measuring the friction coefficient, an operation control unit 7b that controls operations of the load device 4 and the drive device 5, and an input unit 7c that receives input from a test operator. And a display unit 7d for displaying various information on the operation and settings of the testing machine 10 on the screen. The measurement value by the load sensor 6 is sent to the control device 7, and the calculation unit 7a calculates the friction coefficient based on the measured value.

ゴム摩擦試験では、実路面を模擬した試験路面１にゴム試験片２の平坦面を押し当て、その平坦な試験路面１上でゴム試験片２をすべらせながら直進移動させたときの荷重を計測し、試験路面１とゴム試験片２との間の摩擦係数を測定する。静止摩擦係数と動摩擦係数のどちらもが測定可能である。試験路面１に押し当てられるゴム試験片２の圧力条件、並びに、速度や経路などの直進移動に関する条件は、制御装置７によって制御される。移動速度は、ゴム試験片２が所定の区間を一様な速度ですべるように設定されうる。   In the rubber friction test, the load is measured when the rubber test piece 2 is slid straight on the flat test road surface 1 while the flat surface of the rubber test piece 2 is pressed against the test road surface 1 simulating the actual road surface. Then, the coefficient of friction between the test road surface 1 and the rubber test piece 2 is measured. Both static and dynamic friction coefficients can be measured. The pressure condition of the rubber test piece 2 pressed against the test road surface 1 and the conditions relating to the straight movement such as the speed and path are controlled by the control device 7. The moving speed can be set so that the rubber test piece 2 slides in a predetermined section at a uniform speed.

このように、平坦な試験路面１にゴム試験片２の平坦面が押し当てられることにより、ゴム試験片２をすべらせながら直進移動させる際に、接地面積の変化が小さく安定するとともに、接地圧の不均一化を抑制できる。なお、この接地面積は、路面の凹凸に対する真実接触面積ではなく、平板上に押し付けた際に観察される、言わば見かけの接地面積となる。また、試験路面１上でゴム試験片２を旋回移動ではなく直進移動させるので、接地面内での速度差の発生が抑えられる。したがって、この方法によれば、試験路面１とゴム試験片２との間の摩擦係数を精度良く測定することができる。   In this way, the flat surface of the rubber test piece 2 is pressed against the flat test road surface 1, so that when the rubber test piece 2 is linearly moved while sliding, the change in the ground contact area is small and stable, and the ground pressure Can be suppressed. Note that this ground contact area is not a real contact area with respect to the unevenness of the road surface, but is an apparent ground contact area that is observed when pressed on a flat plate. In addition, since the rubber test piece 2 is moved straight on the test road surface 1 instead of turning, the occurrence of a speed difference within the ground contact surface can be suppressed. Therefore, according to this method, the friction coefficient between the test road surface 1 and the rubber test piece 2 can be accurately measured.

ゴム試験片２の直進移動は、直線状経路ＳＲに沿ってゴム試験片２が移動するものであればよく、例えば図２に示した態様が挙げられる。（ａ）では、ゴム試験片２が直線的に移動し、その移動経路が直線状経路ＳＲと合致する。（ｂ）及び（ｃ）では、ゴム試験片２を加振しており、いずれもゴム試験片２がＹ方向に振動しながら直線状経路ＳＲに沿って移動する。微視的に観察すると、（ｂ）は三角波に沿った移動、（ｃ）は正弦波に沿った移動であるが、それらの振動の幅の中心は直線状経路ＳＲと合致しており、かかる移動も直進移動に含まれる。   The straight movement of the rubber test piece 2 may be any movement as long as the rubber test piece 2 moves along the straight path SR. For example, the mode shown in FIG. In (a), the rubber test piece 2 moves linearly, and the movement path thereof coincides with the linear path SR. In (b) and (c), the rubber test piece 2 is vibrated, and both move along the linear path SR while vibrating in the Y direction. When observed microscopically, (b) is a movement along a triangular wave, and (c) is a movement along a sine wave, but the center of the width of these vibrations coincides with the linear path SR, and this takes place. Movement is also included in straight movement.

上記のようなＹ方向の加振に限らず、Ｘ方向の加振やＺ方向の加振を適用することも可能であり、これらも直進移動に含まれる。Ｘ方向に加振する場合は、直線状経路ＳＲに沿った往復動となり、例えば三角波または正弦波による加振が採用される。Ｚ方向に加振する場合は、上下方向に沿った加振となり、例えば三角波、正弦波、パルス波または台形波による加振が採用される。   Not only the excitation in the Y direction as described above but also the excitation in the X direction and the excitation in the Z direction can be applied, and these are also included in the straight movement. When the vibration is applied in the X direction, the reciprocation is performed along the straight path SR, and for example, a vibration using a triangular wave or a sine wave is employed. When oscillating in the Z direction, excitation is performed along the vertical direction, and for example, excitation by a triangular wave, a sine wave, a pulse wave, or a trapezoidal wave is employed.

これに対し、特許文献１，２に記載の従来方法のように試験路面が曲率を有する場合、あるいはゴム試験片の接地面が曲率を有する場合（通常、ゴム試験片を転動させる場合）には、ゴム試験片の接地圧が不均一になる傾向にあり、摩擦係数を測定するのに都合が悪い。また、ターンテーブルの回転面上でゴム試験片を移動させる場合には、ゴム試験片が環状経路を通って旋回移動することになるため、接地面内に生じる速度差に起因して正確な測定が難しくなる。   On the other hand, when the test road surface has a curvature as in the conventional methods described in Patent Documents 1 and 2, or when the ground contact surface of the rubber test piece has a curvature (usually when the rubber test piece is rolled). Is inconvenient for measuring the friction coefficient because the contact pressure of the rubber specimen tends to be non-uniform. In addition, when the rubber test piece is moved on the rotating surface of the turntable, the rubber test piece is swung through an annular path, so that accurate measurement is caused due to the speed difference that occurs in the ground plane. Becomes difficult.

ゴム試験片２の接地面積は、所定の圧力条件において、静止時とすべり移動時とで変化しないことが望ましい。この圧力条件は、乗用車用タイヤに採用するゴム材料の場合では５００〜６００ｋＰａ程度であるが、トラック・バス用タイヤではそれ以上である。また、接地面積の変化を伴うとしても、その面積低下率は２０％以下であることが好ましく、１０％以下であることがより好ましく、５％以下であることが更に好ましい。接地面積の低下を抑えるには、後述するようにゴム試験片の形状を工夫することが有効である。   It is desirable that the contact area of the rubber test piece 2 does not change between a stationary state and a sliding state under a predetermined pressure condition. This pressure condition is about 500 to 600 kPa in the case of a rubber material adopted for a passenger car tire, but is more than that in a truck / bus tire. Further, even if the contact area changes, the area reduction rate is preferably 20% or less, more preferably 10% or less, and further preferably 5% or less. In order to suppress the decrease in the contact area, it is effective to devise the shape of the rubber test piece as described later.

ゴム試験片の面積低下率は（Ｓ１−Ｓ２）／Ｓ１で表され、Ｓ１は静止時の接地面積、Ｓ２はすべり移動時の接地面積である。この面積低下率は、例えば、試験路面のうち摩擦係数の測定に必要となるメイン区間以外のサブ区間に透明なガラス板またはプリズムを取り付け、その上を通るゴム試験片の接地面を撮影して得られた画像により測定することができる。或いは、メイン区間やサブ区間に取り付けた圧力計測装置を用いて測定することもできる。   The area reduction rate of the rubber test piece is represented by (S1-S2) / S1, where S1 is the ground contact area when stationary and S2 is the ground contact area when sliding. This area reduction rate is obtained, for example, by attaching a transparent glass plate or prism to a sub section other than the main section required for measuring the friction coefficient on the test road surface, and photographing the ground contact surface of the rubber test piece passing over it. It can be measured from the obtained image. Or it can also measure using the pressure measuring device attached to the main section or the sub section.

図３に、ゴム試験片２の好ましい形状を示す。（ａ）は、図１と同じ方向から見た正面図であり、この右方向をゴム試験片２のすべり移動の前方とする。（ｂ）は下面図、（ｃ）は右側面図である。ゴム試験片２は、試験路面１に押し当てられる平坦面２ｆを有する。前方側エッジ部の側面２ｓは、その平坦面２ｆから立ち上がっている。この例のように、前方側エッジ部の側面２ｓと平坦面２ｆとが鈍角をなすことが好ましい。これにより、ゴム試験片２をすべらせながら直進移動させた際に、前方側エッジ部が試験路面１に引っ掛かりにくくなり、接地面積の低下や接地圧の不均一化が抑制される。   In FIG. 3, the preferable shape of the rubber test piece 2 is shown. (A) is the front view seen from the same direction as FIG. 1, and let this right direction be the front of the sliding movement of the rubber test piece 2. FIG. (B) is a bottom view and (c) is a right side view. The rubber test piece 2 has a flat surface 2 f that is pressed against the test road surface 1. The side surface 2s of the front edge portion rises from the flat surface 2f. As in this example, it is preferable that the side surface 2s of the front edge portion and the flat surface 2f form an obtuse angle. As a result, when the rubber test piece 2 is linearly moved while sliding, the front edge portion is less likely to be caught on the test road surface 1, and a reduction in contact area and uneven contact pressure are suppressed.

上述のように、角度θ１は９０度を超えることが好ましく、それによって前方側エッジ部の引っ掛かりを抑制できる。この効果を高める観点から、角度θ１は、１００度以上であることが好ましく、１２０度以上であることがより好ましい。また、前方側エッジ部の側面２ｓが試験路面１に接地しないように、角度θ１は１７０度以下であることが好ましく、１５０度以下であることがより好ましい。後方側エッジ部の形状は特に限定されるものではなく、図３では直角に形成されているが、これを前方側エッジ部と同じ形状にしても構わない。   As described above, it is preferable that the angle θ1 exceeds 90 degrees, thereby preventing the front edge portion from being caught. From the viewpoint of enhancing this effect, the angle θ1 is preferably 100 degrees or more, and more preferably 120 degrees or more. Further, the angle θ1 is preferably 170 degrees or less, and more preferably 150 degrees or less so that the side surface 2s of the front edge portion does not contact the test road surface 1. The shape of the rear edge portion is not particularly limited and is formed at a right angle in FIG. 3, but it may be the same shape as the front edge portion.

角度θ１が鈍角である場合、前方側エッジ部の側面２ｓには、図４のような種々の形状を採用できる。このうち（ａ）〜（ｃ）では、それぞれ平坦面２ｆに対して傾斜した傾斜面により側面２ｓが形成されている。（ａ）は図３と同じ形状であり、側面２ｓが角面型の面取り形状をなす。（ｄ）と（ｅ）では、それぞれ湾曲面により側面２ｓが形成されている。（ｄ）の側面２ｓは丸面型の面取り形状をなし、その曲率半径は例えば０．５〜５ｍｍに設定される。（ｅ）の側面２ｓは匙面型の面取り形状をなし、その曲率半径は例えば０．５〜１０ｍｍに設定される。   When the angle θ1 is an obtuse angle, various shapes as shown in FIG. 4 can be adopted for the side surface 2s of the front edge portion. Among these, in (a) to (c), the side surface 2s is formed by an inclined surface inclined with respect to the flat surface 2f. (A) is the same shape as FIG. 3, and the side surface 2 s has a chamfered shape of a square type. In (d) and (e), the side surface 2s is formed by a curved surface. The side surface 2s of (d) has a rounded chamfered shape, and its radius of curvature is set to 0.5 to 5 mm, for example. The side surface 2s of (e) has a saddle face type chamfered shape, and its radius of curvature is set to 0.5 to 10 mm, for example.

図５は、ゴム試験片２の別形状を示す。このゴム試験片２は、半球体の下部を平らにカットした形状をなし、円形の平坦面２ｆを有する。また、このゴム試験片２の側面は全体的に湾曲しており、それに含まれる前方側エッジ部の側面２ｓは湾曲面によって形成されている。図示しないが、下方に向かって先細りする円錐台形状のゴム試験片は、図５に類似した形状を有する。但し、そのゴム試験片の側面は、図４（ｂ）のように全体的に傾斜し、それに含まれる前方側エッジ部の側面は傾斜面によって形成される。   FIG. 5 shows another shape of the rubber test piece 2. The rubber test piece 2 has a shape obtained by flatly cutting the lower part of the hemisphere, and has a circular flat surface 2f. Further, the side surface of the rubber test piece 2 is entirely curved, and the side surface 2s of the front edge portion included in the rubber test piece 2 is formed by a curved surface. Although not shown, the truncated cone-shaped rubber test piece tapering downward has a shape similar to FIG. However, the side surface of the rubber test piece is entirely inclined as shown in FIG. 4B, and the side surface of the front edge portion included in the rubber test piece is formed by an inclined surface.

図６は、ゴム試験片２の別形状を示す。このゴム試験片２には、試験路面１に接触しない厚みを有するブロック２０が連ねられている。かかる形状によれば、ブロック２０がゴム試験片２の動きを抑制し、すべり移動時の接地面積の変化や接地圧の不均一化が良好に抑制される。ブロック２０はＸ方向に連ねられているが、これに代えて、ブロックをＹ方向に連ねても構わない。或いは、ゴム試験片２の周囲を取り囲むように、Ｘ，Ｙ方向を含む全方位的にブロックを連ねることも可能である。ブロック２０の材質は、ゴム試験片２の材質と同じでもよく、違っていてもよい。   FIG. 6 shows another shape of the rubber test piece 2. A block 20 having a thickness that does not contact the test road surface 1 is connected to the rubber test piece 2. According to such a shape, the block 20 suppresses the movement of the rubber test piece 2, and the change in the contact area and the non-uniform contact pressure during the sliding movement are satisfactorily suppressed. The blocks 20 are connected in the X direction, but instead, the blocks may be connected in the Y direction. Alternatively, the blocks can be connected in all directions including the X and Y directions so as to surround the rubber test piece 2. The material of the block 20 may be the same as that of the rubber test piece 2 or may be different.

濡れた路面での摩擦係数を測定する場合には、給水を行って試験路面１上に水膜を形成する。水膜の厚みは、例えば０．１〜３ｍｍに設定される。そして、その試験路面１にゴム試験片２の平坦面２ｆを押し当て、濡れた試験路面１上でゴム試験片２をすべらせながら直進移動させたときの荷重を計測し、濡れた試験路面１とゴム試験片２との間の摩擦係数を測定する。その際、ゴム試験片２の前方側エッジ部の側面２ｓの高さ（図３のｈ寸法）を水膜の厚みよりも大きくすることが好ましい。これにより、高速すべり条件における水膜の抵抗を減らし、測定精度を高めることができる。   When measuring the coefficient of friction on a wet road surface, water is supplied to form a water film on the test road surface 1. The thickness of the water film is set to 0.1 to 3 mm, for example. Then, the flat surface 2f of the rubber test piece 2 is pressed against the test road surface 1, and the load when the rubber test piece 2 is moved linearly while sliding on the wet test road surface 1 is measured, and the wet test road surface 1 is measured. And the rubber test piece 2 are measured for coefficient of friction. In that case, it is preferable to make the height (h dimension of FIG. 3) of the side surface 2s of the front edge part of the rubber test piece 2 larger than the thickness of the water film. Thereby, the resistance of the water film under high-speed sliding conditions can be reduced, and the measurement accuracy can be increased.

ゴム試験片２の平坦面２ｆは、直径２０ｍｍの円形を内包した大きさを有することが好ましい。これにより、試験路面１上を移動するゴム試験片２の平坦面内（即ち、接地面内）に適度な数の骨材９０が含まれ、摩擦係数を精度良く測定できる。したがって、図５のような円形の平坦面２ｆにおいて、その直径は２０ｍｍかそれ以上が好ましい。また、図３のような矩形の平坦面２ｆであれば、２０ｍｍ×２０ｍｍの正方形か、それを内包する大きさの矩形をなすことが好ましい。その場合、平坦面２ｆの面積は４００ｍｍ２以上となる。 The flat surface 2f of the rubber test piece 2 preferably has a size including a circle having a diameter of 20 mm. Thereby, an appropriate number of aggregates 90 are included in the flat surface (that is, in the ground contact surface) of the rubber test piece 2 moving on the test road surface 1, and the friction coefficient can be measured with high accuracy. Therefore, the diameter of the circular flat surface 2f as shown in FIG. 5 is preferably 20 mm or more. In addition, in the case of a rectangular flat surface 2f as shown in FIG. 3, it is preferable to form a 20 mm × 20 mm square or a rectangle of a size including the square. In that case, the area of the flat surface 2f is 400 mm 2 or more.

本実施形態では、試験路面１を固定してゴム試験片２を動かすことで、ゴム試験片２をすべり移動させているが、これに限定されない。ゴム試験片２のすべり移動は、試験路面１に対するゴム試験片２の相対移動を伴うものであればよく、例えばゴム試験片２を固定して試験路面１を動かすことで、ゴム試験片２をすべり移動させてもよい。   In the present embodiment, the rubber test piece 2 is slid and moved by moving the rubber test piece 2 while fixing the test road surface 1, but is not limited thereto. The sliding movement of the rubber test piece 2 only needs to involve the relative movement of the rubber test piece 2 with respect to the test road surface 1. For example, by moving the test road surface 1 while fixing the rubber test piece 2, the rubber test piece 2 is moved. You may move it by sliding.

このような摩擦係数の測定を繰り返して実施するに際し、圧力条件や移動速度を種々に異ならせることで、摩擦係数のマップデータを取得することができる。得られたマップデータは、例えばタイヤのシミュレーションに利用することができ、これによって解析精度を向上できる。また、タイヤの摩擦係数の簡易評価にも利用することができる。   When such measurement of the friction coefficient is repeatedly performed, map data of the friction coefficient can be acquired by varying the pressure condition and the moving speed in various ways. The obtained map data can be used, for example, for tire simulation, thereby improving analysis accuracy. Moreover, it can utilize also for the simple evaluation of the friction coefficient of a tire.

本発明は上述した実施形態に何ら限定されるものではなく、本発明の趣旨を逸脱しない範囲内で種々の改良変更が可能である。   The present invention is not limited to the embodiment described above, and various improvements and modifications can be made without departing from the spirit of the present invention.

本発明の構成と効果を具体的に示すために摩擦係数の測定を行ったので、以下に説明する。試験路面には厚み１ｍｍの水膜を形成し、その濡れた路面に対するゴム試験片の摩擦係数を測定した。表１に示した項目を除き、各例における試験条件は共通である。ゴム試験片は、２８×２８×８（ｍｍ）の直方体形状である。但し、実施例２では、図３で示したように、その前方側エッジ部の側面が角面型の面取り形状（Ｃ１．５）をなし、その側面と平坦面とがなす角度（θ１）は１３５度である。   The friction coefficient was measured to specifically show the configuration and effects of the present invention, which will be described below. A water film having a thickness of 1 mm was formed on the test road surface, and the friction coefficient of the rubber test piece against the wet road surface was measured. Except for the items shown in Table 1, the test conditions in each example are common. The rubber test piece has a rectangular parallelepiped shape of 28 × 28 × 8 (mm). However, in Example 2, as shown in FIG. 3, the side surface of the front edge portion has a square chamfered shape (C1.5), and the angle (θ1) between the side surface and the flat surface is It is 135 degrees.

Figure 2017058244
Figure 2017058244

図７は、摩擦係数の測定結果を示すグラフである。横軸は、ゴム試験片の変位を示し、縦軸との交点はゴム試験片の開始位置（静止状態）である。縦軸は、摩擦係数の測定値を示す。このゴム材料を採用したタイヤの濡れた実路面に対する動摩擦係数は別途に測定済みであり、そのオーダーを破線枠ＢＦで示している。したがって、この破線枠ＢＦにグラフの波形が近付いているほど、摩擦係数が精度良く測定されていることを示す。   FIG. 7 is a graph showing the measurement results of the coefficient of friction. The horizontal axis indicates the displacement of the rubber test piece, and the intersection with the vertical axis is the starting position (stationary state) of the rubber test piece. A vertical axis | shaft shows the measured value of a friction coefficient. The dynamic friction coefficient for a wet actual road surface of a tire employing this rubber material has been measured separately, and the order is indicated by a broken line frame BF. Therefore, the closer the waveform of the graph is to the broken line frame BF, the more accurately the friction coefficient is measured.

図７より、比較例１に比べて、実施例１，２では摩擦係数が精度良く測定されていることが分かる。また、測定後のゴム試験片を観察したところ、実施例１では前方側エッジ部に摩滅が確認されたのに対し、実施例２では確認されなかった。これは、実施例１において、ゴム試験片の前方側エッジ部が試験路面に引っ掛かったか、そうなりかけたことによるものと考えられ、その点において実施例１よりも実施例２の方が好ましいと言える。   From FIG. 7, it can be seen that the friction coefficient is measured with higher accuracy in Examples 1 and 2 than in Comparative Example 1. Moreover, when the rubber | gum test piece after a measurement was observed, although abrasion was confirmed by the front side edge part in Example 1, it was not confirmed in Example 2. FIG. This is considered to be due to the fact that the front edge portion of the rubber test piece was caught on the test road surface in Example 1, or that it was about to happen. In that respect, Example 2 is more preferable than Example 1. I can say that.

１ 試験路面
２ ゴム試験片
２ｆ 平坦面
２ｓ 前方側エッジ部の側面
３ ホルダー
４ 荷重装置
５ 駆動装置
６ 荷重センサ
７ 制御装置
１０ ゴム摩擦試験機
９０ 骨材 DESCRIPTION OF SYMBOLS 1 Test road surface 2 Rubber test piece 2f Flat surface 2s Front side edge 3 Side holder 4 Load device 5 Drive device 6 Load sensor 7 Control device 10 Rubber friction tester 90 Aggregate

Claims (6)

骨材を含んで実路面を模擬してなる試験路面にゴム試験片の平坦面を押し当て、平坦な前記試験路面上で前記ゴム試験片をすべらせながら直進移動させたときの荷重を計測し、前記試験路面と前記ゴム試験片との間の摩擦係数を測定するゴム摩擦試験方法。   Press the flat surface of the rubber test piece against the test road surface that includes the aggregate and simulate the actual road surface, and measure the load when the rubber test piece slides straight on the flat test road surface. A rubber friction test method for measuring a friction coefficient between the test road surface and the rubber test piece. 前記ゴム試験片の前方側エッジ部の側面と前記平坦面とが鈍角をなす請求項１に記載のゴム摩擦試験方法。   The rubber friction test method according to claim 1, wherein a side surface of the front edge portion of the rubber test piece and the flat surface form an obtuse angle. 前記ゴム試験片の前方側エッジ部の側面が傾斜面または湾曲面により形成されている請求項２に記載のゴム摩擦試験方法。   The rubber friction test method according to claim 2, wherein a side surface of the front edge portion of the rubber test piece is formed by an inclined surface or a curved surface. 前記試験路面上に水膜を形成し、濡れた前記試験路面と前記ゴム試験片との間の摩擦係数を測定する請求項２または３に記載のゴム摩擦試験方法。   The rubber friction test method according to claim 2 or 3, wherein a water film is formed on the test road surface, and a friction coefficient between the wet test road surface and the rubber test piece is measured. 前記ゴム試験片の前方側エッジ部の側面の高さが前記水膜の厚みよりも大きい請求項４に記載のゴム摩擦試験方法。   The rubber friction test method according to claim 4, wherein a height of a side surface of the front edge portion of the rubber test piece is larger than a thickness of the water film. 前記平坦面が、直径２０ｍｍの円形を内包した大きさを有する請求項１〜５いずれか１項に記載のゴム摩擦試験方法。   The rubber friction test method according to claim 1, wherein the flat surface has a size including a circle having a diameter of 20 mm.
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