KR20050120931A - Linear displacement transducer with enhanced accuracy - Google Patents

Abstract

In the linear displacement sensor, the contact point of contact with the resistance is changed from the conventional contact point method to the elastic contact point method using the rotating roller made of conductive rubber material to make stable contact point, and the friction is greatly reduced to extend the life of the sensor. Extend. The present invention is a linear displacement sensor for measuring the displacement of the object by the resistance value measured by the contact point contacted between the thin film plate B of the electrical resistance value R _L formed in parallel with the thin film plate A of the zero electrical resistance value A rotational roller is physically connected to one end of the moving shaft that moves in accordance with the movement of the object, and rotates in accordance with the movement of the moving shaft, and has a conductive roller for contacting the thin film plates A and B and forming the contact points. In addition, the average value of the electrical resistance values generated from the contact points formed by the rotational movement of the rotary roller is measured by the displacement.

Description

Linear displacement transducer with enhanced accuracy}

The present invention relates to a linear displacement sensor with improved precision, and in particular, by changing the contact point in contact with the resistance in the linear displacement sensor from the conventional point contact method to the elastic contact point method using a rotating roller made of a conductive rubber material The present invention relates to a linear displacement sensor that achieves stable contact, greatly reduces friction, extends the life of the sensor, and improves precision.

In general, a resistive displacement sensor commonly referred to as a resistive displacement sensor (potentiometer) uses the principle that the electrical resistance value changes with the movement displacement when the contact point on the linear electrical resistor moves. As shown in FIG. 1, when the electrical resistance value of the linear electrical resistor 10 is R _L , the electrical resistance value R _D between the contact B and the contact C is as follows.

<Equation 1>

Where L is the total length of the linear electrical resistor 10, and D is the distance between the B and C contacts. It is assumed that the electric resistor 10 has a uniform resistance value, that is, the displacement (distance) is proportional to the low resistance if it is molded in a linear shape.

Solving <Equation 1> with respect to D is converted to <Equation 2>.

...... <Equation 2>

In Equation 2, since L and R _L are constant values, it can be concluded that R _D can be measured to measure D, that is, displacement. Linear displacement sensors using this principle are widely used in precision machining equipment such as lathes and injection molding machines that require displacement measurement.

 One of the most commonly used linear displacement sensors is GEFRAN, Italy's LTM model, which has a square cross section (not shown). The measuring length of this instrument is determined by the length of the chassis (chassis) ( 50-900mm) The moving axis of circular cross section that forms the contact point inside and outside moves to change the electrical resistance. That is, as shown in Figure 2, the measuring instrument is fixed to the object to measure the displacement of the end of the moving shaft 20 moving along the interior of the square having a cross-section after the change in the electrical resistance according to the movement of the object Measure and measure the displacement movement of the object.

Inside the exterior of the moving shaft 20 is manufactured in the form of a printed circuit board (PCB) 30, a linear resistance plate formed to contact the moving shaft 20 is fixed. As shown in FIG. 2, the movable shaft 20 is manufactured in the form of a printed circuit board (PCB) 30, and a thin film A having an electric resistance value of 0 as a pure conductor material and also a printed circuit board (PCB) 30. It is manufactured in the form of, and is configured to move while contacting through the connecting line 40, which is also a pure conductor material (electric resistance = 0) and the thin film B having an electrical resistance value of R _L as a resistance material.

Therefore, the moving shaft (20) R _D value of the <Expression 2> by a connecting line (40) contacts D, and when measuring the electrical resistance connection lines and the thin film A pure conductor zero Imran electrical resistance to between the E is formed by a moving This is measured. That is, as the moving shaft 20 moves, the connecting line 40 fixed to one end of the moving shaft 20 also moves together, thereby obtaining an R _D value proportional to the displacement of the moving shaft, and measuring up to 550 mm. In the case of LTM-550, when the moving shaft 20 is moved at intervals of several mm and the R _D value is measured, a linear relation as shown in FIG. 3 can be obtained and the D value, that is, displacement is measured from the R _D value measured using the same. Is measured.

However, such a conventional linear displacement sensor basically has a configuration in which the connecting line 40 makes contact with the thin film A and the thin film B, such that the moving shaft 20 and the connecting line 40 connected thereto are rotated (twisted). If there is a problem that the exact displacement is not measured.

      That is, since the thin film B forming the contact point with the connecting line 40 is not a pure conductor but a linear electric resistor formed in the form of a long plate, the electrical resistance value of only one point of the connecting line 40 in contact with the thin film B is measured. do. Therefore, when the moving shaft 20 is not moved in a completely parallel state with the thin film B and the moving shaft 20 is rotated (twisted) as shown in FIG. 4, the position of the contact point is a problem because the thin film A is a pure conductor. However, in the case of the thin film B, there is a problem in that the electrical resistance value measured is changed by changing the position of the contact point in contact with the connecting line 40.

In practice, since the movement axis 20 and the connecting line 40 connected thereto are rarely moved in perfect parallel with the thin films A and B during the measurement of the linear displacement meter, the rotation (or distortion) of the movement axis 20 occurs. The accuracy of displacement measurement is determined by the degree of. In order to freely move the moving shaft forward and backward, some rotational phenomena must be allowed, which causes a problem of deterioration of measurement accuracy.Therefore, the resistance material of the thin film B cannot be perfectly uniform. The problem that the resistance value is different occurs.

In addition, the connection line 40 fixed to the moving shaft 20 forms an elastic contact between the connecting line 40 and the thin film A and the thin film B by applying a constant pressure from the top to form an electrically stable contact. Movement causes unavoidable wear and shortens the life of the device.

   This is caused by the friction between two fixed solids. If the contact pressure is lowered to reduce the friction force, the contact becomes unstable, resulting in contact noise, which also leads to a decrease in measurement accuracy. As a result of measuring the value, as shown in FIG. (Correlation coefficient 0.8596). This occurs because the amount of forward and backward movement of the moving shaft 20 is too small for the amount of rotation. The minimum displacement movement amount is 1 mm as a result of calculating the average value of the correlation coefficient by repeatedly measuring the precision five times for the LTM 550 product. The correlation coefficient was 0.9987 and decreased to 0.8948 at 0.1mm.

The present invention has been invented to solve the above problems, the rotation consisting of a conductive rubber material without forming a contact line contacting the thin film formed of the pure material (electric resistance 0) and the thin film formed of the resistive material in the linear displacement sensor It is composed of rollers to improve the precision by forming the front contact point, and elastic contact is possible by the rotating roller of conductive rubber, so it forms stable contact point and the roller rotates as the moving shaft moves, so the friction is greatly reduced. It is to provide a linear displacement sensor with improved precision that can extend the service life.

The present invention for achieving the above object

In the linear displacement sensor for measuring the displacement of the object by the resistance value measured by the contact point contacted between the thin film plate B with the electrical resistance value of R _L is formed in parallel with the thin film plate A of 0,

It is physically connected to one end of the moving shaft moving in accordance with the movement of the object, the rotational movement in accordance with the movement of the moving shaft, and includes a rotating roller having a conductivity for contacting the thin film plate A and the thin film plate B to form the contact points, the rotation The average value of electrical resistance values generated from the contact points formed by the rotational movement of the roller is measured as the displacement.

In addition, the rotary roller is made of a conductive rubber material.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

6 is a conceptual diagram illustrating a structure of a linear displacement sensor having improved accuracy according to the present invention, and FIG. 7 is a measurement when a rotation (twist) phenomenon occurs when measuring the linear displacement sensor according to the present invention. 8 is a conceptual diagram illustrating the measurement result of the linear displacement sensor according to the present invention.

As shown in FIG. 6, the linear displacement sensor 100 having improved precision according to the present invention has one end fixed to an object to measure displacement, and then a movement axis at the other end of the moving shaft 110 moving according to the object movement. The rotating roller 120 that moves while rotating in accordance with the movement of the 110 is physically connected to the moving shaft 110. The rotary roller 120 is formed of a conductive rubber material having elasticity. The lower part of the rotary roller 120 is a pure conductor material, and the thin film plate A 130 having an electrical resistance value of 0 and the thin film plate B 140 having an electrical resistance value of R _L as a resistance material are formed in parallel with each other. It is formed to contact the roller 120.

That is, the thin film plate A (130) and the thin film plate B (140) is a plate manufactured in the form of a printed circuit board (PCB) by the rotating roller 120 that moves while rotating in accordance with the movement of the moving shaft 110. Is configured to contact. The thin film plate A 130 and the thin film plate B 140 which are in contact with the rotating roller 120 have a front contact point, and the average value of the electrical resistance values of the first contact point formed by contacting the rotating roller 120 is measured. do.

The rotary roller 120 of the linear displacement sensor 100 with improved precision according to the present invention is made of conductive rubber and the material is rubber so that the material has sufficient elasticity, so if the pressure is applied from above, the thin film A 130 and foil Stable elastic contact is made with the membrane B 140. In addition, since the moving shaft 110 rotates naturally as the frictional force is minimized, the friction noise is reduced and the service life is extended.

   When the effect of improving the precision of the linear displacement sensor 100 with improved precision according to the present invention is described, the present invention is fundamentally different from the method using the connection line of the conventional linear displacement sensor, since the rotating roller is cylindrical, Rather, a junction is formed. That is, when the rotary roller 120, the thin film plate A 130, and the thin film plate B 140 made of conductive rubber are in contact with each other, the contact point C and the contact point D are formed as shown in FIG. The pre-contact method in the present invention can prevent a significant decrease in precision due to the rotation (twist) phenomenon during the movement of the moving shaft 110, but how the rotation of the moving shaft will vary greatly depending on the use environment, so the effect of the contact point In order to best explain the same situation as in FIG. 7, assuming that the rotating roller 120 is in contact with the thin film plate B 140 vertically, a contact point having a shape such as “a” of FIG. The average value of the electrical resistance values formed and sensed along the front contact point becomes the actual measurement value. In this case, it is assumed that the rotating roller 120 and the physically fixed moving shaft 110 are rotated in the clockwise direction so that the contact point is rotated from "a" to "me". Since the moved contact point of "I" is rotated about the center of the contact point of "A", when considering the contact point of thin film B 140 and "I", the lower contact point of "I" is a thin film plate. Since the upper end of the contact point "B" of B 140 and the upper end of "I" moves to the right side of the thin film plate B 140 by the same distance, a rotation (or distortion) phenomenon occurs in the moving shaft 110, and thus the new contact point. The average value of the electrical resistance sensed along "I" is equal to "preceding contact point".

      That is, the change in the measured value due to the rotation of the moving shaft generated at the contact point of the linear displacement sensor 100 with improved precision according to the present invention acts in the direction to cancel, thus improving the measurement accuracy.

In order to experimentally verify the effect of the linear displacement sensor according to the present invention, a prototype is manufactured and the result of measuring the electrical resistance by moving the moving shaft 110 at intervals of 0.1 mm is shown in FIG. 8. In Figure 8 it can be seen on the graph that the linearity is significantly improved compared to the conventional point contact method (correlation coefficient 0.9991).

 Since the linear displacement sensor requires accuracy of at least 95% or more, the measurement resolution is limited to 1 mm. The conventional linear displacement sensor described above also has a measurement resolution of 1 mm. As shown in FIG. 8, 0.9987 was obtained as a result of calculating the average value of the correlation coefficient by repeating the same experiment five times. When the rotating roller was used, the measurement precision (or resolution) became 0.1 mm. This means a 10x improvement in resolution or precision when compared to conventional products using connecting lines.

Summarizing the effect of the linear displacement sensor according to the present invention, the precision (resolution) of the measurement is improved from 1mm to 0,1mm, which is 10 times higher, and the friction of the contact is eliminated by the rotating roller, so the wear phenomenon is minimized. Life is extended.

As described above, the linear displacement sensor with improved precision according to the present invention adopts a pre-contact method by a rotary roller rather than a point-contact method, thereby greatly improving accuracy, and elastic contact is possible by a rotating roller made of conductive rubber. Since the roller rotates as the moving shaft moves to form a stable contact point, the friction is greatly reduced, thereby extending the service life.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited thereto and may be improved or modified by those skilled in the art within the scope of the technical idea of the present invention.

1 is a conceptual diagram illustrating the principle of a general resistive displacement sensor.

2 is a conceptual diagram illustrating the operation of a conventional linear displacement sensor.

3 is a graph showing measurement results of a conventional linear displacement sensor.

4 is a conceptual diagram illustrating a problem in measuring a conventional linear displacement sensor.

5 is a graph showing measurement results when a rotation (twist) phenomenon occurs during measurement of a conventional linear displacement sensor.

6 is a conceptual diagram showing the structure of a linear displacement sensor with improved precision according to the present invention.

7 is a conceptual diagram illustrating measurement when a rotation (twist) phenomenon occurs during measurement of the linear displacement sensor according to the present invention.

8 is a graph showing measurement results of the linear displacement sensor according to the present invention.

<Explanation of symbols for the main parts of the drawings>

100: linear displacement sensor 110: moving axis

120: rotating roller 130, 140: thin film

Claims (2)

An electrical resistance value of zero foil late A (130) and formed parallel to the electric resistance value R _L of foil by a resistance value measured by the jeomjeop contact between the late B (140) for measuring the displacement of the object, In the linear displacement sensor, It is physically connected to one end of the moving shaft 110 that moves in accordance with the movement of the object, and rotates in accordance with the movement of the moving shaft 110, and contacts the thin film plate A 130 and the thin film plate B 140. And a rotating roller 120 having conductivity for forming the contact points, and measuring an average value of electrical resistance values generated from the contact points formed by the rotational movement of the rotation roller 120 as a displacement. Linear displacement sensor with improved precision. The linear displacement sensor of claim 1, wherein the rotary roller (120) is made of a conductive rubber material having a certain elasticity.