JP2001337032A - Method and apparatus for testing friction characteristics of elastic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure the friction force inherent in an elastic material sample as objective data with the high correlation with the friction force of a product tire or the like, in testing the friction characteristics of the elastic material sample. SOLUTION: The peripheral surface of the thin-walled cylindrical elastic material sample 6 held by a sample shaft 4 is pressed to a rotationally driven grinding material 1 by required force, in such a posture that the slip ratio of the elastic material sample over the entire width of the grinding material becomes constant to rotationally drive the elastic material sample 6, and the speed of the grinding material 1 and the peripheral speed of the elastic material sample 6 are relatively changed to measure the friction force of the elastic material sample 6 on the basis of generated torque.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the frictional force of various elastic materials, for example, vulcanized rubber, on an abrasive material.
The present invention relates to a method and an apparatus for testing friction characteristics that can be measured with high accuracy under each of dry conditions and wet conditions.

[0002]

2. Description of the Related Art For example, a portable skid tester has been used as a method of measuring friction force and the like, which has been widely used in the past to determine the friction characteristics of tread rubber, which has a great influence on the running performance of a pneumatic tire. And a method of measuring using a flat belt machine.

Here, the former method is, as shown in FIG.
Sample plate 52 on which tread rubber sample 51 is adhered
Is attached to the pendulum 53, and the height of the pendulum 53 is adjusted by the lock screw 55 and the vertical position adjusting screw 56 so that the tread rubber sample 51 properly contacts the road surface material 54. Is fixed to the support arm 57 at a predetermined swing height (90 °), the zero position of the pointer 58 is adjusted, the road surface material 54 is cleaned, and wet or dry conditions are set. The tread rubber sample 51 is brought into frictional contact with the road surface material 54, and the position at which the sample 51 stops is measured by reading the scale plate indicated by the pointer 58.
The latter method measures the driving frictional force, the braking frictional force, and the like by rotating the product tire while pressing it with a required force on a flat running belt laid with a road surface material as an abrasive material. is there.

[0004]

In the former method using a portable skid tester, a test using a tread rubber sample is possible, and a test for various road surface materials is performed under dry and wet conditions. Although there is an advantage that can be achieved, it frictions the end face of the sample having a substantially rectangular parallelepiped shape, and since the contact area largely depends on the rubber hardness, the influence of the hardness of the tread rubber on the measurement result of the friction force is measured. In addition, there is a problem that the frictional force is overestimated with soft rubber, and the pressing force of the tread rubber sample against the road surface material cannot be changed. There was also a problem that the friction force could not be measured.

[0005] For this reason, even if the friction force and the like are measured using a skid tester, it is not possible to rely on the full width of the result. It is unavoidable to separately evaluate the driving and braking performance of the tread rubber, etc. In addition, since this actual vehicle running evaluation is performed based on the driver's sensitivity, quantitative audience data and There was an inconvenience of not being able to do so.

On the other hand, in the latter method using a flat belt machine, even if it is possible to collect spectator data under dry conditions, it is necessary to prototype tires for all tread rubber types developed. With this method, there has been a problem that rapid and efficient development of tread rubber is practically impossible.

SUMMARY OF THE INVENTION An object of the present invention is to solve such problems of the prior art, and it is an object of the present invention to perform a test using an elastic material sample under the action of a required load. This makes it possible to accurately measure the frictional force inherent to the sample, for example, as objective data having a high correlation with that of the product tire, thereby eliminating the need for testing using prototype tires and the like, and speeding up the elastic material. Another object of the present invention is to provide a method and an apparatus for testing a frictional characteristic of an elastic material, which can realize efficient and efficient research and development.

[0008]

SUMMARY OF THE INVENTION A method for testing the frictional characteristics of an elastic material according to the present invention is directed to a method of testing a rotationally driven, for example, annular abrasive material on a peripheral surface of a thin cylindrical elastic material sample held on a sample shaft. Under the posture in which the slip ratio over the entire width is constant, while pressing and rotating with a required force and rotating the polishing material relative to the peripheral speed of the elastic material sample, for example, The friction force when one of them is changed in the range of the slip ratio of 0 to 100% with respect to the other is also measured, for example, as a torque generated on the sample shaft.

The torque measured in this manner can be recorded or displayed as a friction force curve or a friction coefficient curve using the slip ratio as a parameter by inputting the torque to the CPU, for example. It can be displayed as a lock braking force coefficient and a maximum braking force coefficient.

According to such a test method, a braking frictional force, a driving frictional force, and the like are measured while a thin cylindrical elastic material sample is pressed below a required slip ratio on a rotationally driven abrasive material. By effectively preventing the circumferential shear deformation of the sample within its thickness, the effect of the shear deformation on the frictional force, the effect of the hardness of the sample, the contact area, etc. on the frictional force are sufficiently removed. Can be.

[0011] Further, in pressing an elastic material sample against a polishing material with a required force, the pressing force of the sample can be specified sufficiently accurately by taking into account the weight of a sample shaft or the like holding the sample. And on the other hand,
By offsetting the weight with a balance weight or the like, it is possible to press the sample with a smaller force than the weight of the sample shaft or the like.

Further, in this case, the peripheral surface of the elastic material sample is pressed against the abrasive material in a position where the slip ratio over the entire width is constant, and the peripheral surface of the elastic material sample is rotated in the radial direction. By absorbing the perimeter difference, the distribution of the slip ratio in the ground contact surface can be eliminated and uniformized, so that the relative relationship between the slip ratio and the frictional force can be measured more accurately. . In addition, the peripheral speed of the circular abrasive material and the elastic material sample that is rotationally driven is about 2
Since the measurement can be performed at a high speed of 0 km / h which is close to the use condition of the tire, an extremely high correlation result with the measurement result of the tire can be obtained.

Therefore, according to this method, the elastic material sample is pressed against the abrasive material with sufficient pressure regardless of the magnitude of the pressing force as required, and the sample is subjected to the circumferential shear deformation. In addition, the influence of the hardness, the contact area, etc. on the frictional force is so small as to be negligible, and the slip ratio of the entire contact surface of the sample is sufficiently uniform, so that the slip ratio is as expected over the entire width. By setting this constant value, the frictional force corresponding to the slip ratio can be objectively measured with extremely high accuracy.

Thus, under this method, the frictional characteristics of tread rubber and other elastic materials can be accurately obtained as objective data without the necessity of trial production of a product tire or the like. In this way, efficient research and development can be realized.

By the way, in this method, when measuring the friction force while sprinkling water on the polishing material, it is necessary to obtain the friction force of the elastic material under dry conditions as well as the friction force under wet conditions with high accuracy. Can be.

Preferably, the environmental temperature at which the frictional force is measured is appropriately selected to measure the frictional force of the elastic material, which can be, for example, tread rubber, under dry and wet conditions throughout the four seasons. Preferably, the temperature of the water to be sprinkled is appropriately selected to enhance the compatibility of the water temperature with the four seasons. Incidentally, it has been confirmed that the frictional force of the elastic material is more affected by the water temperature than by the amount of water spray.

An apparatus for testing friction characteristics of an elastic material according to the present invention arranges a rotationally driven abrasive material horizontally, holds a cylindrical elastic material sample at one end via a sample holder, and at the other end. A sample shaft to which a motor is connected is arranged at an angle, a torque meter is provided at an intermediate portion of the sample shaft, and a cylinder and other reciprocating drive means for vertically displacing the sample shaft with respect to the polishing material. And a pressing cylinder which is displaced by the reciprocating drive means and presses the elastic material sample held on the sample shaft, for example, a hollow frustoconical sample, against the polishing material with a required force. A load sensor, which can be a load cell or the like, is provided between the pressing cylinder and the sample shaft.

In this apparatus, the elastic material sample attached to one end of the tilted sample shaft via a holder is applied to a polishing material which is rotationally driven by a reciprocating drive means which can be a cylinder, a screw means or the like. In addition to being displaced up to the height, it is displaced down to a position near the abrasive material, and under the action of a pressing cylinder that is displaced up and down together with the tilted sample axis, its peripheral surface is brought into contact with the surface of the abrasive material with a required force. It is pressed accurately, and is also driven to rotate at a required peripheral speed by a motor connected to the other end of the sample shaft.

In this case, the outer contour of the elastic material sample is formed into a tapered frusto-conical shape corresponding to the diameter of the polishing material, which can be formed into a substantially annular shape as a whole, and the inclination of the sample axis is adjusted. Is selected according to its frusto-conical shape, thereby absorbing the difference in the circumferential length of the abrasive material between the inside and outside in the radial direction, so that the entire contact width of the elastic material sample with the abrasive material is reduced with respect to the abrasive material A substantially constant slip ratio is set.

Here, the pressing force of the elastic material sample against the polishing material surface is obtained by detecting the pressing force with a load sensor interposed between the pressing cylinder and the sample shaft.
Preferably, the sample pressing force is used in consideration of the influence of the sample shaft weight and the sample weight. Here, when the balance weight is connected to the middle part of the sample shaft, for example, the position of the center of gravity, to offset the weight of the sample shaft including the motor, the sample holder and the torque meter, the detection result of the load sensor is The pressing force can be accurately obtained only by considering the sample weight, and the sample pressing force can be set to a force smaller than the pressing force corresponding to the sample shaft weight.

Under the condition that the peripheral surface of the elastic material sample is pressed against the surface of the polishing material with the required force in this manner, the frictional force of the sample is, for example, between the polishing material surface and the sample peripheral surface. From the state where both are rotated at the same predetermined speed, the speed of either the sample or the abrasive material is reduced to generate a constant slip between them, and the torque generated on the sample shaft at this time is
It can be measured by measuring with a torque meter provided on the sample shaft.
By performing the process gradually or stepwise in the range of 0%, a braking frictional force or a driving frictional force according to the slip ratio can be obtained.

Thus, according to this device, the elastic material sample can be accurately pressed by the pressing cylinder with the expected force on the abrasive material, and the elastic material sample can be held by the inclined sample shaft. By doing so, in conjunction with the shape of the sample itself, the sample peripheral surface can be pressed against the abrasive material surface without being affected by the radial difference in its circumferential length. It is possible to measure the torque generated in the shaft according to the slip ratio with high accuracy. Therefore, by setting the thickness of the elastic material sample to be thin, the frictional force of the sample can be measured with high accuracy as described above.

In such an apparatus, more preferably, the center of action of the pressing force on the elastic material sample is set at the center of the contact width of the sample with the polishing material, so that the pressing force acts unevenly. Eliminates the possibility of a decrease in measurement accuracy caused by the measurement.

When the polishing material is used as a road surface material, particularly when the elastic material is tread rubber, the frictional force against various road surface materials such as concrete, asphalt, resin, safety walk, etc. It can be measured under roughness.

In this apparatus, when a nozzle for spraying water onto the polishing material is provided, it is possible to perform measurement under wet conditions in addition to frictional force under dry conditions.

In this case, the polishing material and the sample shaft are each stored in a constant temperature chamber, and a cooling means for cooling the constant temperature chamber is provided. More preferably, a heating means in the constant temperature chamber is also provided. In addition to setting the temperature in the constant temperature chamber according to the four seasons in Japan, it is possible to measure the frictional force under the required temperature conditions from extremely cold to extremely hot.

This is the same as when the nozzle is connected to a constant temperature water tank and cooling means for cooling the inside of the constant temperature water tank is provided, and more preferably, when heating means in the constant temperature water tank is also provided. Therefore, the wet frictional force can be measured under the required water temperature condition as long as the water does not freeze.

When the frictional force is measured under the relative slip between the elastic material sample and the abrasive material,
Since the surface recesses of the polishing material are gradually embedded by the shaved sample powder and the like, which may cause the measurement value to fluctuate, preferably, means for cleaning the surface of the polishing material is provided, thereby making the surface necessary. Can be cleaned accordingly. Here, the cleaning means can be a rotating brush pressed against the abrasive material.

[0029]

Embodiments of the present invention will be described below. FIG. 1 is a partial cross-sectional schematic front view showing a main part of an apparatus according to the present invention, and FIG. 2 is a partial cross-sectional schematic line side view showing the entire apparatus.

Here, a road surface material 1 as an example of an abrasive material having a substantially annular shape as a whole is horizontally disposed, and the road surface material 1 is supplied by a motor 2 through a speed reducer 3 to a required speed. Can be driven by rotation.

Here, a sample shaft 4 is disposed in an inclined position above the road surface material 1, and one end of the sample shaft 4 on the road surface material side is provided with an outer contour shape via a sample holder 5. Is a thin-walled cylindrical elastic material sample that is almost frusto-conical,
Here, a thin cylindrical tread rubber sample 6 is detachably held, while a motor 7 for rotating and driving the tread rubber sample 6 at a required peripheral speed is attached to the other end. A torque meter 8 for measuring the generated torque around the axis is provided.

In this case, each of the sample shaft 4 and the motor 7 is attached to the lifting plate 9 on the rear side thereof, and the lifting of the lifting plate 9 with respect to the fixed plate 10 is further performed by the lifting plate 9. In the drawing, a pair of right and left linear motion guides 11 arranged on the rear side are used for guiding, and the vertical displacement of the linear
The operation is performed by the operation of the test section moving cylinder 12 as an example of the reciprocating drive means attached to the zero.

Preferably, the center of gravity of the sample shaft 4 including the sample holder 5, the motor 7 and the torque meter 8, for example, and more preferably, the center of gravity of the sample shaft 4 including the elevating plate 9 via the fixed pulley 13. The balance weights 14 are connected to substantially offset their weight. For example, the hook 14a attached to the lift plate 9 as shown in FIG.
Then, one end of the wire 14b wound around the fixed pulley 13 is hooked, and the balance weight 14 is attached to the other end of the wire 14b. According to this, the sample shaft 4 and the like can be freely moved up and down with a very small external force acting thereon.

Further, in this apparatus, FIG.
As is clear from the right side view along the IV line,
A reduction cylinder 15 that is displaced up and down together with the sample shaft 4 and the like is attached to a rod 12a of a test portion moving cylinder 12 attached to a fixed plate 10 via an intermediate plate 12b, and the reduction cylinder 15 is attached via a rotary bearing 16. To the sample shaft 4, and preferably the lower cylinder 15
Is selected such that the center of the pressing force acting on the tread rubber sample 6 is located at the center of the contact width with the road surface material 1 as shown in FIG. Further, a load sensor for measuring the sample pressing force by the pressing cylinder 15, for example, a load cell 17 is disposed between the pressing cylinder 15 and the sample shaft 4, and preferably, the center axis of the load cell 17 is Then, the sample 6 is positioned so as to be aligned with the center of the road surface material contact width of the sample 6 and the rod axis of the pressing cylinder 15.

In the apparatus constructed as described above, the sample shaft 4 holding the tread rubber sample 6 is moved under the action of the test portion moving cylinder 12 so that the sample 6 is
Can be displaced up and down in parallel between an ascending position where the sample 6 is largely separated from the road surface material and an approaching position where the sample 6 is sufficiently close to the road surface material 1. The road surface material 1 can be pressed with a required force, and the pressing force can be increased or decreased as required.

Here, the frictional force of the tread rubber sample 6 is measured from the state where the road surface material 1 and the sample 6 are both rotated at a constant speed by the respective motors 2 and 7, for example, the respective servomotors, for example. The peripheral speed of the sample 6 is gradually or gradually reduced so that the slip ratio between the sample 6 and the road surface material 1 is changed from 0% to 100%, and occurs at the sample shaft 4 under each slip ratio. The torque in the direction to increase the rotation of the shaft can be obtained by measuring the torque with the torque meter 8, and in this case, the frictional force becomes the braking frictional force.

On the other hand, when the slip is generated by decreasing the speed of the road surface material 1 and when the slip is generated by increasing the peripheral speed of the sample 6, the slip occurs in a direction that hinders the rotation of the sample shaft 4. By measuring the torque, the driving frictional force can be measured.

By the way, in such an apparatus, FIG.
As shown in the figure, when a nozzle 18 for spraying water is provided on the road surface material 1 and the road surface material 1 is made wet by the water spray, various frictional forces can be measured under wet conditions. , The road surface material 1 and the sample shaft 4 are stored in a constant temperature chamber 19, and the constant temperature chamber 1
In the case where a cooling means for cooling the inside 9, for example, a binary refrigerator 20, is provided, the measurement conditions of the frictional force can be adapted to the seasonal temperatures.

In addition, when the nozzle 18 is connected to the constant temperature water tank 21 and the water in the constant temperature water tank 21 is cooled by the binary refrigerator 20, the wet condition is also adapted to the four seasons. be able to.

FIG. 5 is a partial cross-sectional view illustrating a cleaning device which is preferably attached to the above-described device. It is provided at a position opposed to the diameter direction.

This is achieved by disposing a movable plate 31 on which a drive motor 30 is mounted so as to be vertically displaceable under the action of a screw shaft 32 and a lift guide 33 penetrating therethrough. The height relative to the material 1 can be adjusted by rotating the screw shaft 32 by operating the handle 34, while the unexpected rotation of the screw shaft 32 is based on the rotation of the screw shaft lock handle 35.
A boss portion of a brush holder 38 provided with a brush 37 as a cleaning means, which is pressed by the road surface material 1, is provided at the tip end of the output shaft 36 of the drive motor 30 when it can be restrained by the built-in lock bolt. It was attached with screws.

In this cleaning device, the drive motor 30 is displaced downward by operating the handle 34 so that each brush 3
7 is brought into sufficient contact with the road surface material 1, while the contact state is maintained by the screw shaft lock handle 35,
By rotating the drive motor 30, the rubber material adhered to the rotating road surface material 1 can be sufficiently scraped over the entire width thereof.

[0043]

Thus, according to the present invention, the peripheral surface of the thin cylindrical elastic sample is applied to the rotating abrasive material.
By measuring the torque generated on the sample shaft while pressing at the required pressing rate under the required slip rate without causing so-called side slip, by measuring the torque generated on the sample shaft, it is obvious that the Even below, the frictional force corresponding to the slip ratio can be measured with high accuracy with an objective numerical value, so that it is not necessary to manufacture a prototype tire or the like for each elastic material, and the frictional characteristics of each elastic material are high. It can be evaluated under reliability, and therefore, rapid and efficient research and development of elastic materials can be performed.

[Brief description of the drawings]

FIG. 1 is a partial sectional schematic front view showing a main part of an apparatus according to the present invention.

FIG. 2 is a partial cross-sectional schematic line side view showing the entire device according to the present invention.

FIG. 3 is a view showing a lifting plate together with a fixed pulley from the rear side.

FIG. 4 is a right side view taken along the line IV-IV in FIG. 1;

FIG. 5 is a partial cross-sectional view illustrating a cleaning device.

FIG. 6 is a view showing a portable skid tester.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Road surface material 2, 7 Motor 3 Reduction gear 4 Sample shaft 5 Sample holder 6 Tread rubber sample 8 Torque meter 9 Elevating plate 10 Fixed plate 11 Linear guide 12 Test part moving cylinder 12a Rod 12b Intermediate plate 13 Fixed pulley 14 Balance weight 14a Wire 14b Wire 15 Reduction cylinder 16 Rotation bearing 17 Load cell 18 Nozzle 19 Constant temperature chamber 20 Binary refrigerator 21 Constant temperature water tank 30 Drive motor 31 Movable plate 32 Screw shaft 33 Elevating guide 34 Handle 35 Screw shaft lock handle 36 Output shaft 37 Brush 38 Brush holder

Claims (13)

[Claims] 1. A peripheral surface of a thin cylindrical elastic material sample held on a sample shaft is pressed against a rotationally driven polishing material with a required force under a posture in which a slip ratio over the entire width is constant. A frictional property test method for an elastic material, which measures the frictional force based on the generated torque when the polishing material is rotationally driven and the speed of the polishing material and the peripheral speed of the elastic material sample are relatively changed. 2. The method according to claim 1, wherein the frictional force is measured while sprinkling water on the polishing material. 3. The method according to claim 1, wherein the environmental temperature at which the frictional force is measured is appropriately selected. 4. The method according to claim 2, wherein the temperature of the water to be sprinkled is appropriately selected. 5. A rotating polishing material is horizontally disposed, a cylindrical elastic material sample is held at one end via a sample holder, and a sample shaft connected to a motor at the other end is inclined. A torque meter is disposed at an intermediate portion of the sample shaft, and reciprocal drive means for vertically displacing the sample shaft is provided, and the elastic material sample displaced by the reciprocal drive means and held on the sample shaft is polished. An apparatus for testing the friction characteristics of an elastic material, comprising: a pressure reduction cylinder for pressing with a required force; and a load sensor disposed between the pressure reduction cylinder and the sample shaft. 6. The apparatus according to claim 5, wherein a balance weight is connected to an intermediate portion of the sample shaft. 7. The apparatus for testing friction characteristics of an elastic material according to claim 5, wherein the center of action of the pressing force on the elastic material sample is the center of the contact width of the elastic material sample with the polishing material. 8. The polishing material as a road surface material.
An apparatus for testing friction characteristics of an elastic material according to any one of claims 1 to 7. 9. The apparatus according to claim 5, further comprising a nozzle for spraying water on the polishing material. 10. The apparatus for testing friction characteristics of an elastic material according to claim 5, wherein the polishing material and the sample shaft are housed in a constant temperature chamber and cooling means for cooling the constant temperature chamber is provided. 11. The apparatus according to claim 9, wherein the nozzle is connected to a thermostatic water bath and cooling means for cooling the inside of the thermostatic water bath is provided. 12. An apparatus according to claim 5, further comprising means for cleaning an abrasive material. 13. The apparatus according to claim 12, wherein the cleaning means is constituted by a rotating brush pressed against the abrasive material.