JP7649217B2 - Rubber friction test method and rubber friction test device - Google Patents

Description

The present invention relates to a rubber friction testing method and a rubber friction testing device.

To evaluate the frictional properties of rubber materials used in rubber products such as tires, rubber friction tests are conducted using a testing machine installed indoors in which a rubber test piece is pressed and slid on a test surface formed from aggregates, resin, etc. (see Patent Documents 1 and 2).

By the way, when evaluating the frictional properties of rubber materials that are highly temperature-dependent, rubber friction tests are sometimes performed on a test road surface that has been heated to a specified temperature using a heater.

However, in tests using uneven surfaces such as asphalt roads, if a heater is embedded inside the road surface taking into account the strength of the test road surface, the distance (thickness) from the heater to the surface of the test road surface becomes large, and it takes time to heat up to the desired temperature.

It is also possible to heat the surface of the test road by covering it with a heated metal plate, but because the test road surface is uneven, the heat from the metal plate is not easily transferred to the test road surface due to the space between the metal plate and the test road surface, and it takes time to heat it to the desired temperature.

Patent Publication 2005-233797 Patent Publication No. 2017-58244

The present invention was made in consideration of these circumstances, and aims to provide a rubber friction testing method and rubber friction testing device that can heat the test road surface to a desired temperature in a short period of time.

The rubber friction test method of this embodiment is a rubber friction test method in which a test road surface is heated by a heating unit arranged opposite the test road surface, and a rubber test piece is slid on the heated test road surface to measure the friction coefficient between the test road surface and the rubber test piece. In this method, a heat transfer member provided on the heating unit is brought into contact with the test road surface and deformed along the test road surface, and the heating unit is caused to generate heat to heat the test road surface.

The rubber friction test device of this embodiment is a friction test device that includes a test road surface, a heating unit that is arranged opposite the test road surface and heats the test road surface, a holder that holds a rubber test piece and presses it against the test road surface, and a measuring unit that slides the rubber test piece on the heated test road surface to measure the friction coefficient between the test road surface and the rubber test piece, and the heating unit includes a heat transfer member that is in contact with the test road surface and is arranged to be deformable along the test road surface, and transfers heat to the test road surface via the heat transfer member.

In the above-mentioned rubber friction test method and rubber friction test device, the heat of the heating section can be efficiently transferred to the test road surface by a heat transfer member that is in contact with the test road surface and is arranged to be deformable along the test road surface, and the test road surface can be heated to the desired temperature in a short period of time.

FIG. 1 is a schematic diagram showing a rubber friction testing device according to an embodiment of the present invention. FIG. 2 is a diagram showing a state in which a test road surface is heated by a heating unit in the rubber friction test device of FIG. 1.

One embodiment of the present invention will be described below with reference to the drawings. Note that the embodiment described below is merely an example, and any modifications that do not deviate from the spirit of the present invention are considered to be within the scope of the present invention.

The rubber friction test device 10 of this embodiment shown in Figure 1 includes a test road surface 1 simulating an actual road surface, a holder 3 for holding a rubber test piece 2, a load device 4 for pressing the rubber test piece 2 against the test road surface 1, a drive device 5 for moving the rubber test piece 2 relative to the test road surface 1, a load sensor 6 for measuring the load acting on the rubber test piece 2, a control device 7 for controlling the operations required for the test, a heating unit 20, and a temperature sensor 30 for measuring the temperature of the test road surface 1.

The test road surface 1 is a simulation of an actual road surface such as an asphalt road surface. The test road surface 1 is formed by bonding aggregate 1a actually used on roads or hard aggregate 1a having properties equivalent thereto with an adhesive (see Figure 2). Alternatively, the test road surface 1 is formed by cutting out a road surface from an actual road and processing it for measurement. There are no particular limitations on the method of forming the test road surface 1 and other methods may be used. The surface of the test road surface 1 is generally flat, but has irregularities caused by the aggregate 1a.

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 shown in Figure 1, the rubber test piece 2 has a perfect rectangular parallelepiped shape, and its upper surface is adhered to a plate-shaped holder 3. Therefore, the lower surface of the rubber test piece 2 that faces the test road surface 1 becomes the flat surface that is pressed against the test road surface 1.

The holder 3 is connected to a load device 4. The load device 4 is configured to be able to move the holder 3 back and forth along the Z direction (the up and down 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 input to the rubber test piece 2 can be adjusted, and the rubber test piece 2 can be pressed against the test road surface 1 under specified pressure conditions. The load device 4 is configured from a servo motor, but other actuator mechanisms may also be used.

The driving device 5 is configured to be able to reciprocate the table 8 supporting the load device 4 along the X direction (left-right direction in FIG. 1). The movement of this table 8 moves the holder 3, 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 the Y direction (direction perpendicular to the paper surface of FIG. 1) perpendicular to both the X direction and the Z direction. The actuator 9 is used to align the rubber test piece 2 with the test road surface 1 in the Y direction. In this embodiment, the driving device 5 and the actuator 9 are each configured by a servo motor, but are not limited to this.

The load sensor 6 can measure three load components, a vertical component and two horizontal components, and can measure the load in the Z direction (vertical force), the load in the X direction (front-to-back force), and the load in the Y direction (lateral force) acting on the rubber test piece 2. The load sensor 6 is, for example, composed of a load cell. In this embodiment, the load sensor 6 is attached to the upper side of the holder 3 (the side opposite the rubber test piece 2).

The control device 7 includes a calculation unit 7a that performs calculations required to measure the friction coefficient, an operation control unit 7b that controls the operation of the load device 4, the drive device 5, the heating drive unit 25 described later, and the like, an input unit 7c that receives input from the test operator, and a display unit 7d that displays various information on the operation and settings of the rubber friction test device 10 on a 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 measurement value. In other words, in this embodiment, the load sensor 6 and the control device 7 realize a measurement unit that measures the friction coefficient between the test road surface 1 and the rubber test piece 2.

The heating unit 20 is positioned opposite the test road surface 1 as shown in FIG. 2 and heats the test road surface 1 before measuring the coefficient of friction between the test road surface 1 and the rubber test piece 2.

Specifically, the heating unit 20 comprises a heater unit 22, a heat transfer member 24, and a heating drive unit 25. The heating drive unit 25 presses the heated heater unit 22 against the test road surface 1 with the heat transfer member 24 sandwiched therebetween, thereby transferring heat generated in the heater unit 22 to the test road surface 1 via the heat transfer member 24, thereby heating the surface of the test road surface 1 to a predetermined temperature.

The heater section 22 is a flat heating element having a heater and the like, and is arranged so as to face the test road surface 1 in the Z direction. One surface of the heater section 22 is provided with a sheet-shaped heat transfer member 24 that contacts the test road surface 1.

The heat transfer member 24 is sandwiched between the test road surface 1 and the heater section 22 when the heating section 20 heats the test road surface 1, and has the flexibility to deform along the irregularities formed by the aggregate 1a on the surface of the test road surface 1.

The heat transfer member 24 is preferably made of a resin composition having appropriate flexibility, thermal conductivity, and heat resistance, such as silicone resin or acrylic resin. The heat transfer member 24 may be made of a resin composition such as silicone resin or acrylic resin to which a heat stabilizer has been added to improve heat resistance, or a filler may be added.

The hardness of the heat transfer member 24 is preferably a penetration of 40 in accordance with JIS K 2220. If the penetration is 40 or more, the heat transfer member 24 is easily deformed along the unevenness formed on the surface of the test road surface 1, and the contact area of the heat transfer member 24 with the test road surface 1 can be increased, and the proportion of air with low thermal conductivity between the test road surface 1 and the heat transfer member 24 can be reduced, thereby increasing the speed at which heat is transferred from the heating unit 20 to the test road surface 1. There is no particular limit to the upper limit of the penetration of the heat transfer member 24, but a penetration of 80 or less is preferable in terms of ease of handling.

The thermal conductivity of the heat transfer member 24 is preferably higher than that of the aggregate 1a that constitutes the test road surface 1. For example, the heat transfer member 24 preferably has a thermal conductivity of 1 W/m·K or more and 5 W/m·K or less when measured by a hot-wire method in accordance with JIS R 2616.

The heat resistance temperature of the heat transfer member 24 is preferably, for example, 100°C or higher. In this specification, the term "heat resistance temperature" refers to a temperature at which the physical properties of the material are not substantially impaired even when the material is exposed to the temperature, and may be a continuous use temperature (long-term heat resistance temperature) or a short-term heat resistance temperature. The short-term heat resistance temperature may be the melting point in the case of a crystalline organic material, or the glass transition temperature in the case of a non-crystalline organic material.

The thickness of the heat transfer member 24 is preferably equal to or greater than the maximum height of the unevenness formed on the surface of the test road surface 1. By making the thickness of the heat transfer member 24 equal to or greater than the maximum height of the unevenness formed on the surface of the test road surface 1, the proportion of air with low thermal conductivity between the test road surface 1 and the heat transfer member 24 is kept small, and the contact area of the heat transfer member 24 with the test road surface 1 is increased, thereby reducing the thermal resistance between the heat transfer member 24 and the test road surface 1, and the heat of the heater section 22 can be efficiently transferred to the test road surface 1. In addition, in order to reduce the thermal resistance of the heat transfer member 24 itself, the thickness of the heat transfer member 24 is preferably equal to or greater than 1 mm and equal to or less than 3 mm.

In addition, the heat transfer member 24 adheres to the heater section 22 when pressed against the heater section 22 due to the nature of the material of the heat transfer member 24, without being coated with, provided with, or impregnated with an adhesive, but preferably has the property (self-adhesiveness) of being able to be peeled off without transferring to the heater section 22 when peeled off.

The heating drive unit 25 is configured to be able to move the heating unit 20 back and forth along the X and Z directions. The heating drive unit 25 adjusts the position of the heating unit 20 in the X direction so that the heat transfer member 24 faces the test road surface 1 in the Z direction, and then appropriately sets the position of the heat transfer member 24 in the Z direction, thereby adjusting the Z-direction load input to the heat transfer member 24 and pressing the heat transfer member 24 against the test road surface 1 under specified pressure conditions.

In the rubber friction testing device 10, first, as shown in FIG. 2, the driving device 5 moves the table 8 to one side in the X direction, and then the heating driving unit 25 positions the heating unit 20 so that it faces the test road surface 1 in the Z direction. Then, while generating heat from the heater unit 22, the heating driving unit 25 presses the heat transfer member 24 against the upper surface of the test road surface 1, deforming the heat transfer member 24 so that it conforms to the irregularities formed on the surface of the test road surface 1. In this way, the heat generated by the heater unit 22 is transferred to the test road surface 1 via the heat transfer member 24, heating the test road surface 1.

When the temperature detected by the temperature sensor 30 reaches a predetermined temperature, the heating drive unit 25 moves the heating unit 20 in the Z direction to separate the heat transfer member 24 from the test road surface 1, and moves the heating unit 20 to the other side in the X direction (see Figure 1).

Then, as shown in FIG. 1, the driving device 5 moves the table 8 to the other side in the X direction, and the holder 3 is positioned above the test road surface 1. The flat surface of the rubber test piece 2 is then pressed against the test road surface 1, and the load is measured when the rubber test piece 2 is caused to slide in a straight line on the test road surface 1 heated to a predetermined temperature, and the static friction coefficient and dynamic friction coefficient friction between the test road surface 1 and the rubber test piece 2 are measured.

In the rubber friction test device 10, the pressure conditions of the heat transfer member 24 pressed against the test road surface 1, the pressure conditions of the rubber test piece 2 pressed against the test road surface 1, and conditions related to linear movement such as speed and path are controlled by the control device 7. In addition, the moving speed of the rubber test piece 2 is set so that the rubber test piece 2 slides at a uniform speed in a specified section.

In this embodiment, the heat transfer member 24 is brought into contact with the test road surface 1 and deformed along the test road surface 1 while the heating unit 20 generates heat to heat the test road surface 1. Therefore, even if the surface of the test road surface 1 is uneven, an air layer is unlikely to form between the heating unit 20 and the test road surface 1, and the contact area with the heating unit 20 can be increased. Therefore, the surface of the test road surface 1 can be heated to the desired temperature in a short time by a simple method without processing the test road surface 1.

In this embodiment, since the heat transfer member 24 has self-adhesive properties, the heat transfer member 24 can be provided in close contact with the heater section 22, and the heat transfer member 24 can be easily attached to the test road surface 1, so that the heat from the heater section 22 can be efficiently transferred to the test road surface 1.

Reference Signs List 1: Test road surface, 1a: Aggregate, 2: Rubber test piece, 3: Holder, 4: Load device, 5: Drive device, 6: Load sensor, 7: Control device, 7a: Calculation unit, 7b: Operation control unit, 7d: Display unit, 10: Rubber friction test device, 20: Heating unit, 22: Heater unit, 24: Heat transfer member, 25: Heating drive unit,

Claims (6)

Heating the test road surface by a heating unit arranged opposite the test road surface;
A rubber friction testing method in which a rubber test piece is slid on a heated test surface to measure a friction coefficient between the test surface and the rubber test piece,
A rubber friction testing method in which a heat transfer member provided in the heating section is brought into contact with the test road surface and deformed along the test road surface, and the heating section is caused to generate heat to heat the test road surface. The rubber friction test method according to claim 1, wherein the heat transfer member has a heat resistance temperature of 100°C or higher. The rubber friction test method according to claim 1 or 2, wherein the heat transfer member has self-adhesive properties. The rubber friction test method according to any one of claims 1 to 3, wherein the thermal conductivity of the heat transfer member is higher than that of the aggregate that constitutes the test road surface. The rubber friction test method according to any one of claims 1 to 4, wherein the resin constituting the heat transfer member is either a silicone resin or an acrylic resin. Test surface;
A heating unit disposed opposite the test road surface and heating the test road surface;
A holder for holding a rubber test piece and pressing it against the test road surface;
a measurement unit for measuring a coefficient of friction between the test surface and the rubber test piece by sliding the rubber test piece on the heated test surface,
The heating section is provided with a heat transfer member that is in contact with the test road surface and is deformable along the test road surface, and the rubber friction testing device transfers heat to the test road surface via the heat transfer member.

Images