JPH0344656B2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a slip resistance measuring device.

(Prior Art) The trailer method and the portable tester method are widely used as methods for measuring the slip resistance of a road surface.

The trailer method is a method in which the brakes are applied to wheels traveling at a fairly high speed, and the force required to tow the wheels, which are normally completely locked, is measured, and the slip resistance is determined from this. This method has the disadvantage that it is not possible to measure while the vehicle is running at low speed or stopped because it requires the wheels to run at high speed.

The portable tester method is a method in which a slider attached to a pendulum measures the contact friction resistance with the road surface during pendulum motion, and calculates the sliding resistance from this. According to this method, in order to make accurate measurements, it is necessary to precisely adjust the vertical installation of the main body and the length of the slider's contact with the road surface, and these adjustments must be made every time the installation is moved. The disadvantage is that it is not possible to perform accurate movement measurements.

(Problems to be Solved by the Invention) An object of the present invention is to enable continuous measurement of the slip resistance of a surface such as a road surface even when moving at low speed or stopping.

(Means for solving the problem) The present invention maintains a constant rotational speed regardless of fluctuations in the applied torque, and the excitation current changes proportionally to fluctuations in the torque. The driving wheel is rotated, and the rotating sliding wheel is caused to slide on the surface to be tested, and from the torque generated when rotating while sliding in this way,
It is characterized by measuring the slip resistance of the surface to be tested.

When a sliding wheel is brought into contact with a surface to be tested under a constant load, the torque generated in the sliding wheel is proportional to the sliding resistance of the surface to be tested. Therefore, by measuring the torque, the slip resistance can be determined. The torque is proportional to the excitation current of the DC motor rotating the sliding wheel. Therefore, by measuring this excitation current,
Slip resistance is required.

The present invention is also characterized in that the sliding wheel is brought into contact with and pressurized intermittently against the surface to be tested. If this is measured on a wet test surface, if contact pressure is continued continuously, the liquid between the test surface and the sliding ring will be removed immediately and the state will become close to dry, or The situation becomes unstable. In this case, it is no longer possible to expect measurements that correspond to the actual condition of the surface under test. However, if the contact is made intermittently as described above, there will be a period of no contact, during which the wet state will be restored, making it possible to perform measurements with excellent reproducibility.

Further, the present invention is characterized in that a sliding wheel, a sliding wheel motor for rotating the sliding wheel, a swinging mechanism for swinging the sliding wheel, etc. are mounted on a truck, and a movable wheel is provided on the truck. By providing movable wheels on the trolley in this way, it is possible to continuously measure the slip resistance while the trolley is running at low speed, and it is also possible to measure the slip resistance while the trolley is stopped. can also be executed.

(Example) An example of the present invention will be described with reference to the drawings.1
is a trolley, which can be moved to any desired location by means of moving wheels 2. 3 is a swing mechanism, and a load motor 4
It mainly consists of a load cell 6 having one end fixed to the rotating shaft 5, and is swingable about the rotating shaft 5 by the rotation of the load motor 4.

A support frame 7 is fixed to the free end side of the load cell 6 so as to hang therefrom.
A sliding wheel 8 and a sliding wheel motor 9 for rotating the sliding wheel 8 are installed therein. A tire made of, for example, neoprene rubber is installed on the outer surface of the sliding wheel 8, so that it comes into sliding contact with the surface to be tested.
This sliding contact is performed intermittently by the rotation of the load motor 4 described above.

The swing mechanism 3 and other components described above are mounted on the truck 1 as shown in the figure.

As can be understood from the characteristic diagrams shown in FIG. 6, the sliding wheel motor 9 maintains a constant rotational speed even if the torque changes, and when the rotational speed is set, the output and excitation current change. A type with a characteristic that increases or decreases in proportion to torque is used. Specifically, commercially available brushless DC motors are suitable.

The operation of the above configuration will be explained with reference to FIGS. 4 and 5. When the power is turned on to each circuit and motor shown in FIG. 4, the rotational torque from the load motor 4 acts on the load cell 6, and the weight of the sliding wheel 8, etc. suspended from it acts on the load cell 6 and balances it. In this attitude, the load cell 6 has zero output.

In this way, when the output of the load cell 6 is zero,
The load motor 4 is rotated forward by the load motor driver 11, and the load cell 6 is rotated in a direction to lower the sliding wheel 8 that is suspended from the load cell 6. When it lands on the surface to be tested, a set load is applied to the sliding wheel 8 and the sliding wheel motor 9. As a result, the load cell 6 outputs an output, and this output gradually increases as the load motor 4 rotates.

The output of the load cell 6 is given to a level setter 14 via an amplifier 12 and a period setter 13, where it is set to a set value P (see FIG. 5).
same as below. ) compared to When the set value P is reached, the load motor 4 is reversely rotated by the load motor driver 11 based on the output from now on.

This reversal causes the output of the load cell 6 to gradually decrease. When this becomes zero, the load motor 4 starts to stop. When the inertial rotation due to this ends and stops, the load motor 4 starts normal rotation again. Thereafter, this rocking motion of the load cell 6 is repeated.

In the process of the above operation, the peak value of the load applied to the sliding wheel 8 is constant due to the operation of the control string from the load cell 6 to the load motor 4. When the sliding wheel 8 lands on the surface to be tested, the sliding wheel 8 rotates while slipping. The friction coefficient of the surface to be tested at this time is output as the rotational torque of the drive wheel motor 9. This rotational torque is actually generated by the sliding wheel motor 9.
is proportional to the excitation current. Therefore, this excitation current may be detected by the sliding wheel motor driver 15 that rotates the sliding wheel motor 9.

As mentioned above, the load cell 6 is driven by the load motor 4.
is repeatedly oscillating, so the output of the load cell 6, that is, the load applied to the sliding wheel 8, is the fifth
As shown in the figure, it becomes a sawtooth wave. Note that t in FIG. 5 indicates the time when the sliding wheel 8 lands. Therefore, the output from the sliding wheel motor driver 15, that is, the excitation current of the sliding wheel motor 9 also becomes a sawtooth wave, which is amplified by the DC amplifier 16, and then the peak value is output from the output terminal 18 by the peak holder 17. Output. Alternatively, the peak value may be supplied to the recorder output circuit 19 and recorded by the recorder.

The friction coefficient of the surface under test is now a as shown in Figure 5.
When the friction coefficient increases from b to b, the excitation current of the sliding wheel motor 9 also increases correspondingly due to the increase in the coefficient of friction (see FIG. 5). Therefore, as shown in FIG. 5, the peak value of the excitation current, that is, the output voltage of the peak holder 17, varies from c to d.
increases to

The output voltage of this peak holder 17 corresponds to the friction coefficient of the surface to be tested, so from the output voltage of this peak holder 17, that is, the output of the output terminal 18, the friction coefficient after the change in the surface to be tested is calculated. , therefore, slip resistance is required.

It will be easily understood that when the coefficient of friction of the surface to be tested decreases, the behavior described above will be opposite.

In the configuration shown in the figure, the level P set by the level setter 14 is output from the load value output circuit 20.

In this invention, as described above, the sliding wheel 8 is made to land on the test surface intermittently. If this is not done intermittently, and if there is liquid between the surface to be tested and the sliding wheel 8, then
Either the liquid is immediately removed by the continuous sliding of the sliding wheels, resulting in a nearly dry state;
or become unstable. However, if this is done intermittently, the time necessary for the infiltrated surface to fully recover after each measurement will be given, and therefore measurements with excellent reproducibility during infiltration will be possible.

Note that this intermittent period is appropriately set by adjusting the sliding period of the load cell 6 by, for example, adjusting the rotation speed of the load motor 4 using the period setting device 13.

(Effects of the Invention) As detailed above, according to the present invention, it is possible to continuously measure the slip resistance of the surface to be tested such as a road surface even when moving at low speed or stopping. This has the advantage that measurement can be performed without impairing the wettability of the surface to be tested.

[Brief explanation of drawings]

Fig. 1 is a front view showing one embodiment of the present invention, Fig. 2 is a side view of the same, Fig. 3 is a partial perspective view, Fig. 4 is a block diagram showing the configuration of this invention, and Fig. 5 is a FIG. 6 is a time chart for explaining the operation, and is a characteristic diagram of the rotation speed, exciting current, and output car torque of the sliding wheel motor. 3... Swinging mechanism, 4... Load motor, 6... Load cell, 8... Sliding wheel, 9... Sliding wheel motor.

Claims (1)

[Claims] 1. A sliding wheel motor consisting of a sliding wheel and a DC motor that rotates the sliding wheel at a constant speed, and a sliding wheel motor that rotates the sliding wheel at a constant speed, and periodically rotates the sliding wheel until a constant load is applied to the surface to be tested by swinging and pressurizing the sliding wheel. a swinging mechanism for swinging the sliding wheel, a cart on which the sliding wheel, the sliding wheel motor, and the swinging mechanism are mounted; a movable wheel provided on the cart for making the cart freely travel; a measuring device that measures the torque generated in the sliding wheel motor when a certain load is applied to the driving wheel, and the sliding resistance of the test surface is measured from the torque measured by the measuring device. measuring device.