JP3929155B2 - Coefficient of friction measurement device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a friction coefficient measuring apparatus, and more particularly to a portable friction coefficient measuring apparatus that can measure the relationship between a slip ratio and a friction coefficient on an actual road surface to be measured at the stage of a test piece.
[0002]
[Prior art]
Conventionally, as a portable rubber friction coefficient measuring device, for example, there is a pendulum type measuring device. In this apparatus, a rubber test piece is attached to the lower end of the pendulum, and when the pendulum is shaken, the friction coefficient is obtained from the height when the test piece is moved by rubbing the test surface. There is also a proposal for a measuring apparatus in which a test piece is fixed to a rotating body and pressed against a test surface to obtain a friction coefficient. However, the friction coefficient that can be measured from these devices is a friction coefficient with a constant slip ratio, and there is a problem that the relationship between the slip ratio and the friction coefficient when the slip ratio is changed cannot be obtained.
[0003]
Regarding the relationship between the slip ratio and the friction coefficient, even if the rubber is the same, the friction coefficient is greatly different if the slip ratio is different. Therefore, especially in automobile tires, in order to facilitate the development of tires with excellent braking performance, a portable type that can be measured on the actual road surface where the relationship between the slip ratio and the friction coefficient is to be measured at the stage of the test piece. A proposal of a friction coefficient measuring device has been strongly desired.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a portable friction coefficient measuring apparatus capable of measuring a relationship between a slip ratio and a friction coefficient on an actual road surface to be measured at the stage of a test piece.
[0005]
[Means for Solving the Problems]
In the present invention for achieving the above object, the first drive motor is installed at the center of the standing frame so that the drive shaft hangs downward, and the rotating body is fixed to the lower end of the drive shaft. A rubber test piece support shaft having a horizontal axis as a rotation axis is horizontally disposed on the rotating body so that a tip support portion protrudes from the rotating body in a radial direction of the rotating body, and a rear end of the support shaft is rotated. It is connected to a second drive motor installed on the body via a driving force measuring means.
[0006]
In this way, the rotating body is attached to the lower end portion of the driving shaft of the first driving motor, and the rubber test piece supporting shaft is installed on the rotating body so that it can be rotated to the second driving motor via the driving force measuring means. Therefore, the rubber test piece mounted on the tip support portion of the rubber test piece support shaft can be rotated by the second drive motor, while the rotating body provided with the support shaft for supporting the test piece by the first drive motor is provided. Since it can rotate, by adjusting the rotational speed of both drive motors, it can roll on the road surface while generating a desired slip on the test piece. Therefore, it is possible to measure the friction coefficient of the rubber test piece according to the slip ratio using the driving force detected by the driving force measuring means.
[0007]
Also, a rotating body is attached to the lower end portion of the drive shaft of the first drive motor installed on the frame, and the rubber test piece support shaft is connected to the second drive motor installed on the rotary body via the driving force measuring means. Therefore, since the apparatus can be simplified and reduced in size, it can be carried and measurement can be performed by moving on the road surface to be actually measured.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
1 and 2 show an example of a friction coefficient measuring apparatus according to the present invention. In this measuring apparatus, a first drive motor 2 is installed at an upper central portion of a standing frame 1 and its drive shaft 2a faces downward. It comes to be drooped. A central portion of a disk-shaped rotating body 3 having an upper and lower surface in a horizontal direction is fixed to a lower end portion of the drive shaft 2a.
[0009]
On one side of the rotating body 3, a second drive motor 4 that rotates a rubber test piece X formed in a disk shape, a torque detector 5 that detects the torque of the rubber test piece X, and a rubber at the tip A rubber test piece support shaft 6 that supports the test piece X is provided. The rear end of the rotary shaft 5a of the torque detector 5 is connected to the tip of the drive shaft 4a of the second drive motor 4 extending in the radial direction of the rotary body 3 via the coupling 7, and passes through the torque detector 5. The tip of the extending rotary shaft 5a is also used as a rubber test piece support shaft 6. The support shaft 6 extends horizontally in the radial direction of the rotating body 3, and is horizontally provided so that the tip support portion 8 protrudes from the rotating body 3. A rubber test piece X is detachably fixed to the tip support portion 8 by a nut N.
[0010]
According to the measuring device as described above, the rubber test piece X attached to the tip support portion 8 is rotated by the second drive motor 4, and the rotating body 3 on which the test piece X is placed by the first drive motor 2. Can rotate. Therefore, by adjusting the rotational speeds of the drive motors 2 and 4, the rubber test piece X can be rolled on the road surface R while causing a desired slip. Therefore, the friction coefficient of the rubber test piece according to the slip ratio can be easily measured using the torque 検 出 detected by the torque detector 5.
[0011]
That is, the driving force F is calculated from the torque 検 出 (= F × r: r is the radius of the test piece) detected by the torque detector 5. If F is the rolling resistance RR when the slip ratio = 0, the friction coefficient μ can be obtained from the equation μ = (F−RR) / W. However, W is the weight of the rubber test piece X in a state where it is mounted on the tip support portion 8. This weight W is measured with a platform scale installed on the road surface before the friction test. The slip ratio can be obtained from the equation (Vt−Vr) / Vt, where Vt is the rotational speed of the rubber specimen X and Vr is the rotational speed of the rotating body 3. However, the slip ratio = 0 when Vt = Vr. Therefore, if the slip ratio and the driving force F corresponding to the slip ratio are obtained, the friction coefficient at each slip ratio is calculated from the above equation, and the relationship between the slip ratio and the friction coefficient can be obtained. FIG. 3 shows an example in which the relationship between the slip ratio and the friction coefficient is measured.
[0012]
Further, the rotating body 3 is attached to the first driving motor 2 installed on the frame body 1, and the rubber test piece support shaft 6 is connected to the second driving motor 4 installed on the rotating body 3 via the torque detector 5. Therefore, the device can be simplified, downsized, and portable. Therefore, it becomes easy to measure by moving on the road surface to be actually measured.
[0013]
FIG. 4 shows another example of the friction coefficient measuring apparatus of the present invention. In this embodiment, in the embodiment described above, a balance for attaching a balance piece Y having the same shape as the test piece X to the position P on the rotating body 3 on the side opposite to the side where the rubber test piece support shaft 6 is provided. A single support shaft 9 is installed. The balance piece support shaft 9 is horizontally attached to the upright support pieces 10 and 10 and is rotatable about the horizontal direction. Further, the rotary body 3 is provided in the radial direction, and the tip support portion 9 a protrudes from the rotary body 3. In this way, by installing the balance piece support shaft 9 on the opposite side and attaching the balance piece Y to the tip support portion 9a at the time of measurement, in addition to the above-described effects, it is possible to carry out balance travel with the two left and right rotating pieces. The burden applied to the drive shaft 2a that supports the rotating body 3 can be reduced.
[0014]
In the present invention, the rotating body 3 is formed in a disk shape in the above embodiment, but instead, it is formed in a rectangular plate shape as shown in FIG. A rubber test piece support shaft 6 may be attached, and the rotating body 3 is preferably substantially point-symmetrical in plan view with respect to the center of rotation.
Further, it is preferable that the balance weight K is detachably mounted at the position P of the rotating body 3 on the side opposite to the side where the support shaft 6 is provided. Uneven lateral shake of the drive shaft 2a can be suppressed.
[0015]
In the above embodiment, the torque detector 5 is used to measure the driving force F. However, if the driving force F can be measured, another driving force measuring means may be used.
The present invention can be suitably used for measuring the relationship between the slip ratio and the friction coefficient at the stage of the rubber test piece, but in addition to this, the actually produced pneumatic tire is used as the test piece. Can also be used.
[0016]
【The invention's effect】
As described above, in the present invention, the first drive motor is installed at the center of the standing frame so that the drive shaft hangs downward, and the rotating body is fixed to the lower end of the drive shaft. A rubber test piece support shaft having a horizontal axis as a rotation axis is disposed on the rotating body so that a tip support portion projects from the rotating body in a radial direction of the rotating body, and a rear end of the support shaft is disposed on the rotating body. Since the two drive motors are connected to each other through the driving force measuring means, it is possible to roll the rubber test piece on the road surface while generating any slip, so that the slip ratio-friction coefficient Since the relationship can be easily measured and carried, measurement on the actual road surface to be measured becomes possible.
[Brief description of the drawings]
FIG. 1 is a front view showing an example of a friction coefficient measuring apparatus according to the present invention.
FIG. 2 is a view taken in the direction of arrows AA in FIG.
FIG. 3A is a graph showing an example of a relationship between slip ratio and friction coefficient on a dry paved road surface, and FIG. 3B is a graph showing an example of a relationship between slip ratio and friction coefficient on a wet paved road surface.
FIG. 4 is a front view showing another example of the friction coefficient measuring apparatus according to the present invention.
FIG. 5 is a plan view showing another example of a rotating body provided with a second drive motor, a torque detector, and a rubber test piece support shaft in the friction coefficient measuring apparatus of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Frame 2 1st drive motor 2a Drive shaft 3 Rotating body 4 2nd drive motor 5 Torque detector (drive force measuring means)
6 rubber test piece support shaft 8 tip support portion 9 balance piece support shaft 9a tip support portion K balance weight P opposite position R road surface X rubber test piece Y balance piece

Claims (5)

The first drive motor is installed in the center of the standing frame so that the drive shaft hangs downward, the rotary body is fixed to the lower end of the drive shaft, and the rotary body rotates in the horizontal direction. A rubber test piece support shaft serving as a shaft is laid horizontally so that a tip support portion protrudes from the rotating body in a radial direction of the rotating body, and a rear end of the supporting shaft is mounted on a second driving motor installed on the rotating body. A friction coefficient measuring device connected via a driving force measuring means. At the position opposite to the side where the test piece support shaft is installed on the rotating body, a rotatable balance piece supporting shaft with the horizontal direction as an axis protrudes from the rotating body in the radial direction of the rotating body. The friction coefficient measuring device according to claim 1, which is installed horizontally. The friction coefficient measuring device according to claim 1 or 2, wherein the rotating body has a substantially point-symmetric shape in plan view with respect to the center of rotation. The friction coefficient measuring apparatus according to claim 3, wherein the rotating body has a disk shape or a rectangular plate shape. The friction coefficient measuring device according to claim 3 or 4, wherein a balance weight is attached to a position of the rotating body opposite to a side where the rubber test piece support shaft is installed.

Images