JPH0347699B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a friction coefficient measuring device that can be effectively used for comparatively measuring the surface roughness of a large number of products. be.

[Prior Art] When two objects are in contact, a frictional force is inevitably generated between them along the tangential direction of the contact surfaces. This frictional force not only depends on the state of the surfaces of the two objects that are in contact with each other, but also depends on the pressure force between the two objects, that is, the drag force that acts in the normal direction.

Therefore, determining the frictional force in relation to the above-mentioned drag force, that is, determining the friction coefficient expressed as the ratio of the drag force to the frictional force, is very important in understanding the contact state of objects.

Comparatively measuring the friction coefficients of a number of objects with respect to one reference surface is also effective for detecting the surface properties, characteristics, etc. of those objects.

Conventionally, in order to obtain this friction coefficient, the above-mentioned drag force and frictional force were each measured separately, and the coefficient was calculated from these measured values. Therefore, there was a problem that the coefficient of friction could not be measured directly and easily.

[Problems to be Solved by the Invention] A technical problem of the present invention is to provide a measuring device that can directly and easily measure the coefficient of friction at a contact surface with an object.

[Means for Solving the Problems] In order to solve the above problems, a friction coefficient measuring device of the present invention includes a flat elastic spacer and a surface pressure sensor that sandwiches the spacer from both sides, and the surface pressure sensor An elastic spacer is fixed on the support through one of the two surface pressure sensors, and the surface of the other surface pressure sensor is used as the contact surface against the object, and the center of gravity of the force acting on those surface pressure sensors is measured. It is constructed by attaching means.

[Function] The friction coefficient measuring device having the above configuration is supported by a support body, presses the surface pressure sensor on the surface and the object against each other, and at the same time applies a force in the tangential direction of the contact surface with the object. By applying a , the coefficient of friction can be determined from the deviation of their center of gravity positions. In other words, due to the positional deviation between the point of action of the drag force acting between the object and the surface pressure sensor and the point of action of the drag force acting between the other surface pressure sensor and the support, the thickness of the measuring device itself In consideration of this, it is possible to measure the coefficient of friction between the surface of the surface pressure sensor, which is a reference surface, and the object.

[Effects of the Invention] According to the present invention, an extremely simple and inexpensive measuring device for measuring the friction coefficient of an object can be provided.

[Example] Before describing the example of the present invention, the principle underlying the present invention will be described.

In FIGS. 1 and 2, 1 is a support to which a friction coefficient measuring device is attached, and 2 is a surface pressure sensor 4.
A flat elastic spacer is fixed to the support 1 through a plate-shaped elastic spacer, and 3 and 4 are surface pressure sensors that are attached to sandwich the elastic spacer 2 from both sides. The surface of the sensor 3 is used as a contact surface against the object 5.

Therefore, the friction coefficient measuring device is fixed on the support 1, and the friction coefficient of the object 5 is measured with the surface of the surface pressure sensor 4 as a reference.

In this device, when the object 5 and the surface pressure sensor 3 are not pressed against each other, the elastic spacer 2 is in the state shown by the chain line in FIG. 2.

When the object 5 and the surface pressure sensor 3 are brought into pressure contact with each other and a drag force N ₁ is applied between them and a frictional force F ₁ is applied at the same time, the elastic spacer 2 is moved as shown in FIG. The state shown by the chain line is deformed as shown by the solid line, and a drag force N ₂ equal to the drag force N 1 and a friction force F ₁ are generated between the _surface pressure sensor 4 and the support 1 as well.
A frictional force F ₂ equal to .

The point of action B of the above drag force N ₂ and friction force F ₂ is the drag force
With respect to the point of action A of N ₁ and frictional force F ₁ , drag forces N ₁ and N ₂
is shifted by a distance l in a direction perpendicular to the direction of action of. The distance l is determined from the moment balance condition as follows: l=h·F ₁ /N ₁ (1) where h: the thickness of the elastic spacer 2 and the surface pressure sensors 3 and 4. Since F ₁ /N ₁ in this equation is the coefficient of friction, if the thickness h is kept constant, the coefficient of friction can be determined by determining the distance l.

Note that the thickness h is such that the pressing force between the object 5 and the surface pressure sensor 3 is not so large, and the influence of the amount of deformation due to the pressing is greater than the measurement accuracy of the coordinate values of the point of force application, which will be explained below. Since it is relatively small, it can be considered constant.

Therefore, in order to find the above distance l, drag force N ₁ ,
It is necessary to measure the coordinate values of the application points A and B of N ₂ , and by measuring this with the surface pressure sensors 3 and 4, the coefficient of friction F ₁ /N ₁ can be determined.

The present invention measures the coefficient of friction based on the above principle, and examples thereof will be specifically described below.

In the friction coefficient measuring device shown in FIGS. 1 and 2, the elastic spacer 2 is deformed by the action of forces from two opposing surfaces, and is made of any material such as sponge. can be used.

In addition, the coordinate values of the points of action A and B of the drag forces N ₁ and N ₂ are sent to the surface pressure sensors 3 and 4 that sandwich the upper and lower surfaces of the elastic spacer 2 . A means (detection circuit) is attached to detect the position of the center of gravity (pressure).

Detecting the center of gravity position of surface pressure using such a surface pressure sensor is a conventionally known technique, and in the present invention, these known surface pressure detection means can be used. An example will be explained with reference to FIG.

The surface pressure sensor shown in the figure consists of a first layer of sheet resistor 11 made of a flexible material with high conductivity, and pressure-sensitive conductive rubber whose conductance changes approximately linearly under the action of external pressure. Second layer pressure sensitive plate 12
and a third layer of sheet resistor 13 formed of the same material as the first layer of sheet resistor 11, and these are basically square shaped. The first layer of the sheet resistor 11 has electrodes 15 and 1 on a pair of opposite sides in the x direction.
6, and electrodes 17, 1 are provided on a pair of opposite sides in the y direction perpendicular to the x direction on the third layer sheet resistor 13.
There are 8. Substantially the same configuration is adopted even when the surface has a planar or curved shape other than a square.

Surface pressure sensors 3 and 4 having such a configuration
are the electrodes 15 at both ends of the first layer sheet resistor 11,
A voltage +a is applied to each of the electrodes 16 through the resistor R, and the electrodes 1 at both ends of the third layer sheet resistor 13
The voltages V _A and V _B of the electrodes 15 and 16 and the voltages of the electrodes 17 and 18 when a force acts on the surface pressure sensor are Take out the voltages V _C and V _D.

FIG. 4 shows a circuit configuration for determining the sum of the surface pressures, that is, the drag force N ₁ =N ₂ and the coordinates (,) of the center of gravity, based on the voltages of the respective electrodes. , ₁₆ are input to the subtraction circuits 21, 22, 23, and the voltage +a applied to the electrodes 15, 16 via the resistor R is input to the subtraction circuits 21 _, 23. By guiding the outputs a-V _A and a-V _B from 21 and 23 to the addition circuit 24, the sum of the surface pressures applied to the surface pressure sensor, that is, the drag force N ₁ =N ₂ , is calculated as N ₁ =N ₂ = k ₀ (2a−V _A −V _B ) …(2) (where k ₀ is a constant) is obtained from the output of the adder circuit 24, and further,
The output from the addition circuit 24 and the output from the subtraction circuit 22 are input to the division circuit 25, and the coordinate value of the center of gravity position (,) is calculated as follows: =k ₁ V _A −V _B /2a−V _A −V _B ...(3) (However, k ₁ is a constant).

Also, regarding the other coordinate values y at the center of gravity position (,), using the circuit configuration that is substantially the same as in Fig. 4 above, =k ₂ V _C −V _D /2a+V _C +V _D …(4) (However, k ₂ is a constant).

In this case, the denominator (2a + V _C +
Similarly to (2a-V _A -V _B ) in equation (2), V _D ) also corresponds to the drag force applied to the surface pressure sensor, and therefore, N ₁ = N ₂ = k ₀ (2a-V _A - The total surface pressure can be determined as V _B ) = k ₀ (2a + V _C + V _D ).

The measuring device having the above structure supports the surface pressure sensor 3 and the object 5 on the surface by pressing them against each other, and at the same time applies force in the tangential direction of the contact surface with the object to create friction. When a force is generated, the center of gravity of the force acting on the surface pressure sensors 3 and 4 on the upper and lower surfaces of the elastic spacer 2, that is, the coordinate values of the application points A and B in FIG. ，
4, and the deviation between these two coordinate values, that is, the positional deviation corresponding to the distance l in FIG. 2 can be measured.

Therefore, the coefficient of friction of the contact surface with the object can be determined from the deviation of the coordinate values and the thickness h in FIG. 2.

Note that by using the surface pressure sensor configured as described above, the contact force acting thereon and the contact position can be measured at the same time.

[Brief explanation of drawings]

FIG. 1 is a perspective view schematically showing an embodiment of the present invention;
Figure 2 is an explanatory diagram for explaining the measurement principle.
FIG. 3 is a perspective view of the surface pressure sensor, and FIG. 4 is a configuration diagram of an arithmetic circuit connected thereto. DESCRIPTION OF SYMBOLS 1... Support body, 2... Elastic body spacer, 3, 4... Surface pressure sensor, 5... Target object.

Claims (1)

[Claims] 1 Equipped with a flat elastic spacer and a surface pressure sensor that sandwiches it from both image sides, the elastic spacer is fixed on a support via one of the surface pressure sensors, and the surface of the other surface pressure sensor is 1. A friction coefficient measuring device, characterized in that a contact surface is used as a contact surface against an object, and a means for measuring the position of the center of gravity of a force acting on the surface pressure sensor is attached to the surface pressure sensor.