JPH05203510A - Method and apparatus for measuring frictional force - Google Patents

Abstract

PURPOSE:To measure frictional force readily and highly accurately by making magnetomotive force act on a movable body, which is held on the main body of a measuring device without contact, imparting vertical drag without contact, bringing the movable body into contact with the measuring surface for friction, and making the magnetomotive force act on the movable body without contact so as to impart horizontal force. CONSTITUTION:Magnetomotive force is made to act on a movable body 1, which is held in a measuring-device main body 2, and arbitrary vertical drag is imparted without contact so as to have contact with the measuring surface of friction. Magnetomotive force is made to act on the movable body 1 without contact so as to impart horizontal force, and frictional force is measured. The magnetomotive force is made to act and the movable body 1 is driven. Thus, the arbitrary magnetomotive force is generated by, e.g. adjusting the amount of the current of a magnetomotive- force generator and so on. In this way, the force, which is applied on the movable body 1, can be arbitrarily set. When driving force is imparted to the movable body 1 under the non-contact state, frictional heat is not generated. The movable body is brought into contact vertically with respect to the measuring surface. The frictional force is measured highly accurately without the fluctuation of the contact area of the movable body 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frictional force measuring method and a measuring apparatus therefor.

[0002]

2. Description of the Related Art As a conventional friction force measuring device, Japanese Patent Laid-Open No.
There is one disclosed in Japanese Patent Laid-Open No. 1-258145. This frictional force measuring device measures a frictional force (tangential force) in order to measure the sliding strength of a rotating sliding member 22 such as a magnetic disk. Specifically, as shown in FIG.
The arm member 20 having the sliding element 21 that contacts the sliding member 22 attached to one end is rotatably attached to the frame 26 by the pin 27, and the sliding member is attached by the weight 25 attached to the base end portion of the arm member 20. The structure is such that the load applied to 22 can be adjusted, and each of the above-mentioned components is rotatable in the horizontal plane by the fulcrum 24 of the frame 26. A force that blocks this turning power is applied and the force applied at that time is rubbed. The frictional force detection means 23 which detects as a force is provided.

The principle of measuring the frictional force of this frictional force measuring device will be described with reference to FIG. Here, fulcrum 5
The frictional force detection means 23 is provided at a position at a distance B from the fulcrum 5
It is assumed that the sliding element 21 is attached to the tip of the arm member 20 at a distance A from. Now, it is assumed that the rotational moment in the illustrated state is acting on the fulcrum 24, and at that time, the sliding member 2
When the vertical load Fl is applied to 2, the frictional force Ft works correspondingly in the x direction. The frictional force Ft at this time is expanded to A / B by the lever action. The frictional force Ft in the balanced state is measured by generating a reaction force Fc that balances the A / B expanded force.

[0004]

However, in the case of the above-mentioned frictional force measuring device, since the load is adjusted by the weight 25 attached to the base end portion of the arm member 20, the load, that is, the vertical drag force is arbitrary. Difficult to adjust. Further, in the case of this measuring device, frictional heat is generated because the sliding member 22 and the measuring system are integrally connected, and accurate measurement cannot be performed due to the influence of this frictional heat. Also,
There is a problem in that the area of the contact surface changes due to the load applied to the sliding element 21, which causes a measurement error. That is, there is a problem that the frictional force cannot be measured easily and with high accuracy.

The present invention has been made in view of the above points, and an object of the present invention is to provide a frictional force measuring method and a measuring apparatus therefor capable of easily and highly accurately measuring the frictional force. is there.

[0006]

According to the present invention, in order to achieve the above object, a magnetomotive force is applied to a movable body held in a non-contact state in a main body of a measuring machine so as to generate an arbitrary normal force without contact. The frictional force is measured by applying a horizontal force to the movable body in a non-contact manner by applying a magnetomotive force thereto.

When measuring the static frictional force and the static frictional coefficient, a horizontal force is applied to the movable body while the movable body is in contact with the friction measuring surface by an arbitrary vertical drag force, and this horizontal force is increased. The horizontal force at the time when the movable body starts to slide is defined as the static friction force, and the static friction coefficient may be calculated from this static friction force and the vertical drag force. Further, when measuring the dynamic friction force, the movable body also slides on the friction measurement surface by moving the measuring device main body while the movable body is in contact with the friction measurement surface by an arbitrary vertical drag force. The holding force in the moving direction of the movable body may be measured as the dynamic friction force.

Further, as a method of measuring the coefficient of dynamic friction, a method of contacting a friction measuring surface with an arbitrary vertical drag force,
It is only necessary to apply an arbitrary horizontal force to move it for an arbitrary distance, measure the time required at this time, and calculate the dynamic friction coefficient of the movable body. Further, a holding means for holding the movable body in a non-contact state in the measuring machine body so as to be movable within a specific plane, and a driving force for the movable body in the non-contact direction in a direction orthogonal to the specific plane and in a horizontal direction. Drive means to be applied, position detection means for detecting the position of the movable body within a specific plane in a non-contact manner, and control for performing constant control and variable control of the drive force of the drive means according to the detection output of this position detection means By including the means, it is possible to configure a frictional force measuring device that realizes each of the above measuring methods.

If the driving means is capable of driving the movable body in all three-dimensional directions, the frictional force can be measured in any direction regardless of the installation state of the measuring device.

[0010]

According to the present invention, an arbitrary magnetomotive force is generated by applying a magnetomotive force to the movable body by driving the movable body as described above, for example, adjusting the amount of current of the magnetomotive force generator. The force can be set arbitrarily, and by applying the driving force to the movable body in a non-contact state, frictional heat is not generated, and the movable body can be contacted perpendicularly to the measurement surface to measure the frictional force. You can do it, there is no change in the contact area of the movable body,
Highly accurate friction force measurement is possible.

[0011]

EXAMPLES Examples of the present invention will be described below. The frictional force measuring method will be described first, and then the measuring device that realizes the measuring method will be described. A method of measuring the static friction force and the static friction coefficient will be described with reference to FIGS. FIG. 1 is a schematic structure of the measuring device, and includes a movable element 1 that contacts the member X to be measured, and a measuring machine main body 2 that applies a driving force for measuring the frictional force to the movable element 1. Consists of. Here, the movable body 1 is held in contact with the inside of the measuring machine body 2, and the measuring machine body 2 can apply an arbitrary driving force in the vertical direction and the horizontal direction with respect to the measurement surface. It should be noted that a detailed description of the configuration that can be made in this way will be described in the structure of the measuring device.

At the time of this measurement, the contact pressure (normal drag force N) of the movable member 1 on the measured surface of the member to be measured X is preset. Then, the movable body 1 is brought into contact with the measurement surface by the normal force N, and the force in the radial direction (horizontal direction) is increased as shown in FIG. At this time, it is determined at the same time whether or not the movable body 1 is slipping. This determination of slippage can be detected from the relative displacement of the position of the movable body 1 shown in FIG. 3, and can be detected by the position sensor 7 and control means described later. Then, the force applied in the radial direction at the time when the slip occurs (the time when the slip starts) is defined as the static friction force F ₀ . Then, from the static friction force F ₀ and the normal force N, the static friction coefficient (μ ₀ = F ₀
/ N). The procedure for measuring the static friction force and static friction coefficient is shown in FIG.

Next, a method of measuring the dynamic friction force will be described with reference to FIGS.
It will be explained based on. Also in this measurement, FIG.
As shown in FIG. 3, the movable body 1 is brought into contact with the measurement surface with a preset vertical drag force N, and in the state where the movable body 1 is brought into contact with this vertical drag force N, as shown in FIG. The movable body 1 is slid along with the movement. Then, the holding force F in the radial direction when the movable body 1 is slipping is measured. The holding force F is defined as a dynamic friction force. The measurement procedure is shown in FIG. 5, and the measurement result is shown in FIG.

A method of measuring the coefficient of dynamic friction will be described with reference to FIGS. In this case, the movable body 1 is positioned at the end of the measuring machine body 2 as shown in FIG. 7B, and the movable body 1 is subjected to friction measurement with a preset normal force N as shown in FIG. 7C. Touch the surface. Then, a force F ₁ (shown in FIG. 9) that is equal to or greater than the static frictional force F ₀ in the radial direction is applied to the movable body 1 as shown in FIG.
It is moved as shown in (d). Here, this moving distance x ₁ is within a range in which position measurement is possible. Then, to measure the time required t ₁ of the moving distance x _1. From this measurement result, the acceleration α is calculated using the following equation (1).

X ₁ = (1/2) αt ₁ ² (1) Then, the dynamic friction coefficient μ is calculated from the obtained acceleration α using the following equation (2). mα = F ₁ −μN The measurement procedure is shown in FIG. 8 and the measurement result is shown in FIG. 9.

FIG. 10 shows a triaxial control type frictional force measuring device. In this measuring apparatus, the movable body 1 is housed in a measuring machine body 2 having a space formed from the lower surface and both side surfaces to the inside, and compressed air is passed through air inflow holes 2a formed on both sides of the measuring machine body 2. The movable body 1 is restrained in a horizontal plane with a low frictional force by flowing into the void of the measuring machine body 2. That is, the movable body 1 is held by a so-called air bearing structure.

The movable body 1 has a structure in which a DC actuator is used to control three degrees of freedom in the vertical direction, the horizontal direction and the rotation, and a voice coil motor (VCM) 3 is used as the DC actuator. The voice coil motor 3 is composed of a rectangular annular voice coil 4 and an E-shaped permanent magnet 5 fitted in the central piece 5a in a non-contact state. The voice coil 4 applies a current to the voice coil 4. The voice coil 4 is controlled to be movable in the longitudinal direction of the central piece.

In the case of this frictional force measuring device, FIG.
As shown in (a), the voice coil motors 3 are attached to both sides and the upper portion of the movable body 1, so that the three degrees of freedom in the vertical direction, the horizontal direction, and the rotation can be controlled. The voice coil motor 3 is shown in FIG.
As shown in 0 (a) and (c), the permanent magnet 5 is fixedly attached to the measuring machine body 1, and the voice coil 4 is fixed to the movable body 1. The voice coil motors 3 on both side surfaces have voice coils 4 mounted movably in the vertical direction, and the voice coil motors 3 mounted on the upper surface have voice coils 4 mounted movably in the horizontal direction. Here, the control in the vertical direction is performed by changing the amount of current supplied to the voice coil 4 of the voice coil motor 3 attached to both sides of the movable body 1, and the control in the horizontal direction is performed in the horizontal direction. This is performed by changing the amount of current supplied to the voice coil 4 of the voice coil motor 3 attached to the upper part. In addition, the vertical plane (Fig. 1
The rotation control within the plane (a) is parallel to the vertical and horizontal directions by varying the amount of current supplied to the voice coil 4 of each voice coil motor 3. Be seen.

Sensor targets 6 are attached to the respective voice coils 4, and the positions of these sensor targets 6 are detected by a position sensor 7. The output of these position sensors 7 is used to control the amount of current supplied to the voice coil 4 to freely control the position and force of the movable body 1 in three degrees of freedom. The control means of this voice coil motor 3 is shown in FIG.
As shown in, feedback control needs to be performed in consideration of the interaction of forces acting on the three voice coil motors 3. Therefore, in the present embodiment, this control means is configured by using an arithmetic processing unit composed of a microcomputer capable of high-speed matrix arithmetic processing. Energization to the voice coil 4 is performed via a current supply unit (for example, an amplifier) 12,
The output of the position sensor 7 is given to the arithmetic processing unit 11 via the interface unit 14, and the control output according to the arithmetic result is supplied to the current supply unit 12 via the interface unit 14.
Given to. The current supply unit 12 receives a power supply from the power supply unit 13 and supplies a current to the voice coil 4.

By using this frictional force measuring device, it is possible to measure the static frictional force, the static frictional coefficient, the dynamic frictional force and the dynamic frictional coefficient by executing the various frictional force measuring methods described above. Moreover, with this frictional force measuring device, the vertical drag force applied to the movable body 1 can be arbitrarily set by the control of the voice coil motor 3. Further, since the movable body 1 and the measuring device main body 2 are not in contact with each other, frictional heat is not generated and the frictional force can be measured with high accuracy. Furthermore, the vertical reaction force can be applied to the friction surface from the vertical direction regardless of the magnitude of the vertical reaction force. Therefore, the contact area of the friction force surface does not change due to the vertical reaction force, and the ideal surface contact state is obtained. The frictional force can be measured with, and from this point as well, the frictional force can be ideally measured with high accuracy. According to this frictional force measuring device, the voice coil motor 3 moves the movable body 1
Since the force applied to is proportional to the value of the current flowing through the voice coil 4, there is an advantage that the control is easy. If the measurement surface of the member to be measured X is a spherical surface or a cylindrical surface, the frictional force on the curved surface can be measured.

FIG. 12 shows the structure of another frictional force measuring device. In the case of the above-mentioned frictional force measuring device, the direct current actuator composed of the voice coil motor 3 is used. However, this frictional force measuring device uses the electromagnet device 8 and uses the attraction force of the electromagnet device 8. As in the frictional force measuring device shown in FIG. 10, vertical, horizontal, and rotational degrees of freedom are controlled. The electromagnet device 8 is formed by winding a coil 10 around a U-shaped iron core 9.

In this frictional force measuring device, a T-shaped movable body 1 is used, and the electromagnet devices 8 are arranged on the inner surfaces of the lateral sides of the movable body 1 of the measuring machine body 2 facing each other.
The electromagnet device 8 is arranged on each of the inner surfaces of the lateral pieces on the opposite sides of the upper and lower surfaces thereof. In the case of this frictional force measuring device, the control of the movable body 1 in the vertical direction is performed by controlling the magnetomotive forces of the four electromagnet devices 8 arranged vertically, and the control in the horizontal direction is performed on both sides. The electromotive force of each electromagnet device 8 is controlled, and further rotation is performed by each electromagnet device 8.
Control.

Also in the case of this frictional force measuring apparatus, the static frictional force, the static frictional coefficient, the dynamic frictional force and the dynamical frictional coefficient can be measured by using the above-mentioned various frictional force measuring methods. It has the same effect as the case. Moreover, in the case of this frictional force measuring device, since the magnetomotive force is proportional to the square of the value (I / w) obtained by dividing the current I flowing in the coil 10 by the gap w of the gap, a large output can be obtained in a small gap range. be able to. In this case, it is necessary to form the movable body 1 with a magnetic body. It is also possible to utilize the repulsive force instead of the suction force.

In the case of the above-described frictional force measuring device, the movable body 1 can be planarly controlled in posture (the frictional force can be measured linearly on the measuring surface), but the measurement is performed as shown in FIG. The structure may be such that the frictional force can be measured in any direction of the surface. FIG. 14 shows the structure of the frictional force measuring device. In this frictional force measuring device, three voice coil motors 3 are attached to the upper part of the movable body 1 at positions different by 120 degrees, and the voice coil motors 3 are positioned at intermediate positions between the attachment positions of the voice coil motors 3 and 120 A structure in which three voice coil motors 3 are attached at different positions, the upper three voice coil motors 3 perform horizontal control, and the lower three voice coil motors 3 perform vertical control. There is. Although only one permanent magnet 5 of the voice coil motor 3 is shown in FIG. 14, it goes without saying that the voice coil motor 3 is composed of the voice coil 4 and the permanent magnet 5, respectively. With this structure, control in all three-dimensional directions, that is, 6 axes (X, Y, Z, θx, θy, θz) becomes possible. The frictional force can be measured in any direction even if the 5-degree-of-freedom control other than the rotation θz of the Z axis is performed.

Further, FIG. 15 shows an improved response of the frictional force measuring device. In this frictional force measuring device, the detection arm 1b is provided so as to project horizontally from the movable body 1,
The tip of the detection arm 1b is bent downward, and a spherical friction surface 1a is formed on the tip surface. With this structure, the inertial force can be reduced.

[0026]

As described above, the present invention applies a magnetomotive force to a movable body held in a non-contact state in the measuring machine body to give an arbitrary vertical drag force in a non-contact manner to bring it into contact with a friction measurement surface. ,
The frictional force is measured by applying a magnetomotive force to the movable body in a non-contact manner to give a horizontal force. By driving the movable body by applying the magnetomotive force, for example, By generating an arbitrary magnetomotive force by adjusting the amount of current, the force applied to the movable body can be set arbitrarily, and by applying the driving force to the movable body in a non-contact state, friction heat does not occur, Moreover, the frictional force can be measured by contacting the movable body perpendicularly to the measurement surface, and the contact area of the movable body does not change, and the frictional force can be measured with high accuracy.

Further, a horizontal force is applied to the movable body in a state in which the movable body is brought into contact with the friction measuring surface by an arbitrary vertical drag force, and this horizontal force is increased so that the horizontal force at the time when the movable body starts to slide. The static friction force and the static friction coefficient are calculated from the static friction force and the normal force, so that the static friction force and the static friction coefficient can be easily and highly accurately measured. Further, by moving the measuring device body while the movable body is in contact with the friction measuring surface by an arbitrary vertical drag force, the movable body also slides on the friction measuring surface, and the holding force in the moving direction of the movable body at this time is obtained. If the dynamic friction force is measured, the dynamic friction force can be measured easily and with high accuracy.

Further, while being in contact with the friction measuring surface by an arbitrary vertical drag force, it is moved by an arbitrary horizontal force for an arbitrary distance, and the time required at this time is measured to calculate the dynamic friction coefficient of the movable body. By doing so, the dynamic friction coefficient can be measured easily and with high accuracy. Further, a holding means for holding the movable body in a non-contact state in the measuring machine body so as to be movable within a specific plane, and a driving force for the movable body in the non-contact direction in a direction orthogonal to the specific plane and in a horizontal direction. Drive means to be applied, position detection means for detecting the position of the movable body within a specific plane in a non-contact manner, and control for performing constant control and variable control of the drive force of the drive means according to the detection output of this position detection means By providing means, it is possible to realize each of the above measurement methods,
Moreover, each frictional force and friction coefficient can be measured easily and highly accurately.

Further, if the driving means is capable of driving the movable body in all three-dimensional directions, the frictional force can be measured in any direction regardless of the installation state of the measuring device.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a method of measuring a static friction force and a static friction coefficient according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a measurement procedure of the above.

FIG. 3 is an explanatory diagram of a measurement output in the above.

4 (a) and 4 (b) are explanatory views showing a method for measuring a dynamic friction force.

FIG. 5 is a flowchart showing a measurement procedure of the above.

FIG. 6 is an explanatory diagram of measurement output in the above.

7 (a) to 7 (e) are explanatory views showing a method of measuring a dynamic friction force coefficient.

FIG. 8 is a flowchart showing a measurement procedure of the above.

FIG. 9 is an explanatory diagram of measurement output in the above.

10A to 10C are respectively a front sectional view, a side sectional view, and a plan sectional view showing a frictional force measuring device.

FIG. 11 is a block diagram showing a circuit configuration of the above control circuit.

12A to 12C are respectively a front sectional view, a side sectional view, and a plan sectional view showing another frictional force measuring device.

FIG. 13 is a perspective view showing the appearance of still another frictional force measuring device.

FIG. 14 is a partially cutaway perspective view showing the structure of the above.

FIG. 15 is a perspective view in which a part of the modification example is cut away.

FIG. 16 is a perspective view showing a conventional example.

FIG. 17 is an explanatory diagram of the above measurement principle.

[Explanation of symbols]

 1 movable body 2 measuring machine body X member to be measured

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[Procedure amendment]

[Submission date] July 6, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

[0011]

EXAMPLES Examples of the present invention will be described below. The frictional force measuring method will be described first, and then the measuring device that realizes the measuring method will be described. A method of measuring the static friction force and the static friction coefficient will be described with reference to FIGS. FIG. 1 is a schematic structure of the measuring device, and includes a movable element 1 that contacts the member X to be measured, and a measuring machine main body 2 that applies a driving force for measuring the frictional force to the movable element 1. Consists of. Here, the movable body 1 is held in the measuring machine body 2 in a non- contact state, and the measuring machine body 2 can apply an arbitrary driving force to the measurement surface in the vertical direction and the horizontal direction. It is possible. It should be noted that a detailed description of the configuration that can be made in this way will be described in the structure of the measuring device.

Claims (6)

[Claims] 1. A magnetomotive force is applied to a movable body held in a non-contact state in the measuring machine body to give an arbitrary vertical drag force in a non-contact state to bring it into contact with a friction measurement surface, and the movable body is in a non-contact state. A method for measuring frictional force, which comprises measuring a frictional force by applying a horizontal force by applying a magnetomotive force. 2. A horizontal force is applied to the movable body in a state where the movable body is brought into contact with the friction measurement surface by an arbitrary vertical drag force, and the horizontal force is increased to change the horizontal force at the time when the movable body starts to slide. A method of measuring a frictional force, wherein a static frictional force is defined and a static frictional coefficient is calculated from the statical frictional force and the normal force. 3. The movable body also slides on the friction measuring surface by moving the measuring device main body in a state where the movable body is in contact with the friction measuring surface by an arbitrary vertical drag force, and in the moving direction of the movable body at this time. A frictional force measuring method for measuring a holding force as a dynamic frictional force. 4. A dynamic friction coefficient of a movable body is calculated by measuring a time required at this time by moving an arbitrary distance by applying an arbitrary horizontal force in a state of being in contact with a friction measuring surface by an arbitrary vertical drag force. Friction force measurement method. 5. A holding means for holding the movable body in a non-contact state in the measuring machine body so as to be movable within a specific plane, and non-contact with the movable body in a direction orthogonal to the specific plane and in a horizontal direction. Driving means for applying a driving force, position detecting means for detecting the position of the movable body in a specific plane in a non-contact manner, and constant control and variable control of the driving force of the driving means according to the detection output of the position detecting means. A frictional force measuring device comprising: 6. The frictional force measuring device according to claim 5, wherein the driving means is capable of driving the movable body in all three-dimensional directions.