JPH01233301A - displacement sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a displacement sensor, and more particularly to a displacement sensor that measures length.

(Prior Art) As a part of a mechanical device, a sensor must function accurately over a long period of time in a variety of harsh and fluctuating environments; Since this leads to a decline in the functionality of mechanical devices and systems, a sensor with a simple structure, high accuracy, and reliability is desired.

As conventional displacement sensors of this type for measuring length, those shown in FIGS. 8 and 9 are known, for example.

The one shown in Fig. 8 measures displacement using strain, and both ends of the shirt (1) are rotatably supported by support metals 2.3, and a tension between the support metals 2.3 is used. A bracket 4 is provided at a predetermined portion of the bracket 4.
A second bracket 6 is fixed non-contact to the spring 5 via a spring 5, and the displacement X in the longitudinal direction when the shaft 1 rotates corresponds to the displacement of the spring 5. As a result, the displacement X of the shaft is detected by the strain gauge 7.8 provided on the bracket 6. Note that the strain gauge may be a semiconductor gauge.

On the other hand, in the case shown in FIG.
2 is wound, and the brush 13 is brought into contact with the winding resistor 12, and the position where the fixed brush 13 contacts the entire resistor changes in response to the displacement X in the longitudinal direction of the shaft 11. The voltage applied by a predetermined DC power supply 14 connected to both ends of the wire resistance 12 is measured by a voltmeter 16 connected between the fixed part 15 of the brush 13 and the e side of the DC power supply 14. That is, the winding resistance 12 corresponds to the displacement
The displacement X is detected from the voltage and current values generated in the brush 13 that divides the total resistance of the brush 13.

(Problem to be Solved by the Invention) However, in the former case, the configuration of such conventional displacement sensors is complicated because the displacement of the shaft is detected using a strain gauge or a semiconductor gauge. can be,
It is difficult to improve measurement accuracy. Furthermore, since the signal generated in the gauge is a weak changing component, there is a problem in that the cost including the amplification function is extremely high.

On the other hand, with the latter type that detects changes in resistance,
Since it was configured to include a brush (contactor), there were problems with durability and reliability due to poor contact and wear of the brush.

(Objective of the Invention) Therefore, an object of the present invention is to provide a displacement sensor that has a simple configuration, has high accuracy, and can improve durability and reliability.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the displacement sensor according to the present invention includes a sheet with a three-layer structure in which a stress-sensitive member is placed in the center and conductive members and resistor members are arranged on both sides of the stress-sensitive member; voltage applying means for applying a predetermined voltage to both ends of the resistor member; and voltage detection means for detecting the voltage generated between the resistor member and the conductive member at the end of the sheet; When stress is applied to a predetermined point on the body side, the electrical conductivity of the stress-sensitive member of the seat changes, and the voltage detected by the voltage detection means changes depending on the stress generation point of the seat.

(effect) In the present invention, an electrically conductive member, a stress sensitive member, and

A three-layered sheet made of resistor members is formed, and a predetermined voltage is applied to both ends of the resistor member. When stress is applied to a predetermined point on the resistor side of the sheet, the conductivity of the stress sensitive member changes and the voltage generated between the resistor member and the conductive member at the end of the sheet is detected by the voltage detection means. Ru. In this case, the voltage detected by the voltage detection means changes depending on the stress generation location of the sheet, and corresponds to the displacement from the edge of the sheet.

Therefore, it is possible to accurately detect displacement with a simple configuration and without impairing durability or reliability.

(Example) Hereinafter, the present invention will be explained based on the drawings.

1 to 6 are diagrams showing a first embodiment of a displacement sensor according to the present invention.

First, the configuration will be explained. In FIG. 1, 20 is a sheet. The sheet 20 has a three-layer structure in which copper foil 21 (conductive member), pressure sensitive rubber 22 (stress sensitive member), and resistor film 23 (resistor member) are bonded together as shown in the figure. The thickness of the copper foil 21 is 35 μm, and the thickness of the pressure sensitive rubber 22 is 50 μm.
The thickness of the resistor film 23 is 15 μm, and the thickness of the entire sheet is about 100 μm.

The resistor film 23 can be formed by bonding foil-like materials or by printing on the upper layer of the pressure-sensitive rubber 22. The seat) 20 is designed to flexibly deal with bending force.

In FIG. 2, the three-layer sheet 20 as described above is
One end of the sheet 20 cut into a bulk shape of IIIl is fixed with a fixing member 24, and the other end is fixed to a movable side (not shown), and the middle part of the sheet 20 is curved into a U shape as shown in the figure. I'm setting it up. Therefore, the curved portion of the seat 20 is configured to move in response to the displacement X on the movable side, that is, the curved portion of the seat 20 is configured to roll in response to relative displacement.

Electrodes A and B and copper foil 2 are placed on both ends of the resistor film 23.
An electrode C is provided at one end of 1, and electrodes A-B
In between, there is a DC power supply 25 with the A electrode on the e side and the B electrode on the ■ side.
(voltage applying means) is connected and a predetermined voltage Vcc is applied. Further, a voltmeter 26 (voltage detection means) is connected between the electrodes A and C, and the voltmeter 26 detects the potential difference generated between the copper foil 21 and the resistor film 23.

Here, in order to supplementally explain the properties of the resistor film 23 as a stress sensitive member, the resistor film 23 shown in FIG.
This will be described with reference to the load-resistance characteristic diagram of No. 3. FIG. 3 is a diagram showing a local resistance change when a load is applied to a local part of the resistor film 230. FIG. In the figure, when no load is applied, the resistance is in an insulating state with very high resistance, whereas when a load of approximately 20 g or more is applied from the outside,
It becomes a conductive state of 0Ω or less. In other words, the resistor film 23 instantaneously becomes 2 due to a slight externally applied load.
The characteristic that the resistance changes in value is used to apply it to a displacement sensor like this embodiment. The load corresponds to the stress generated in the curved portion of the sheet 20 in this embodiment.

Next, the effect will be explained.

Before explaining the operation of FIG. 2, the basic operation of this embodiment will be explained using the equivalent circuit shown in FIG. 4.5. FIG. 4 is an equivalent circuit when the sheet 20 has no curved portion and no stress is generated. In Figure 4, each point A, B, C,
V cc corresponds to the electrodes A, B, C1 DC power supply 25 and voltmeter 26 in FIG. 2, ■ is the equivalent resistance between A and B of the resistor film 23, and R is the resistor The combined resistances of the resistances of the pressure-sensitive rubber 22 and W4 foil 21 that are joined in parallel to the film 23 and the joint resistances of the joints between the members are shown. In this case, since the sheet 20 has no curved portion, point D is not shown. At this time, since the resistance of the pressure-sensitive rubber 22 is in an insulating state as described above, almost no current flows through the combined resistance R, and no voltage is detected by the voltage SK.

That is, the pressure sensitive rubber 22 is connected to the copper foil 21 and the resistor film 2.
If we use a switch that conducts between 3 and 3, since this switch is in an open state, no current will flow to the voltage needle.
The reason why the resistor film 23 is closed with sliding resistance is that the curved portion of the sheet 20 moves with respect to the displacement X.

FIG. 5 is an equivalent circuit in the case where the seat 20 has a curved portion as shown in FIG. 2 and stress is generated. In addition to FIG. 4, the figure equivalently shows the local resistance Rσ at the stress generation point and point D. Rσ is generated because stress is applied locally to the pressure sensitive rubber 220 when the sheet 20 is bent, and the local resistance becomes conductive as described above. Since the pressure sensitive rubber 22 remains insulated at the joints other than point D,
The resistance R is approximately equal to R in FIG. Therefore, the voltage VCC applied across (2) 8 is divided by the point D, and the divided voltage is detected by the voltmeter via Rσ. At this time, only the curved portion of the pressure sensitive rubber 22 is in a conductive state, that is, the switch is in a closed state, and current flows between the copper foil 21 and the resistor film 23. The above is the basic operation of FIG.

Returning to FIG. 2 again, the operation will be explained. sheet 20
When the movable side end moves in the left-right direction in the figure, its displacement
The curved portion (stress generation point) D of the sheet 20 is moved correspondingly. At this time, the resistor film 23 is electrically divided between A and B by the conductive portion 22a of the pressure sensitive rubber 22, and this division ratio also changes in accordance with the displacement X. That is,
As shown in Section 6.7, the resistor film 23 and the conductive portion 22a exhibit the same effect as sliding resistance in response to the displacement X. Therefore, the voltage VCC applied between A and B of the resistor film 23 is divided, and the divided voltage causes a current to flow from the resistor film 23 to the copper foil 21 via the conductive part 22a, and A -C is detected as a voltage corresponding to the displacement X by the voltmeter 26 connected between C and C. However, the detected displacement X is limited to a bendable range in the distance between A and B of the sheet 20, and the voltage detected corresponding to the displacement X is limited to the voltage VCC of the DC power supply 25. Such a relationship is as shown in the displacement-voltage characteristic diagram shown in FIG.

Therefore, in this embodiment, by using a sheet 20 with a three-layer structure consisting of a copper foil 21, a pressure-sensitive rubber 22, and a resistor film 23 as a displacement sensor, the configuration becomes very simple, and the displacement to be detected is can be dealt with accurately. Further, since the sheet 20 is in the form of a foil and the pressure sensitive rubber 22 has elasticity, its performance is sufficiently maintained even when repeated stress is applied, improving durability and reliability.

FIG. 7 is a diagram showing a second embodiment of the present invention.
Similarly to the first embodiment, displacement is detected as current and voltage using 0. In the figure, a roller 28 rotatably supported by a support member 27 is rolled on the upper surface of the sheet 20 to apply stress to the sheet 20, and a current and voltage corresponding to the displacement X are detected.

Therefore, the same effects as in the first embodiment can be obtained, and since the sheet 20 is extended in a plane, there is an advantage that the effective distance for detecting displacement can be longer than in the first embodiment.

(Effects) According to the present invention, a sheet with a predetermined 3N structure is formed, a stress corresponding to displacement is applied to the sheet, and a potential difference due to a change in conductivity generated in a stress-sensitive member of the sheet is detected. Displacement can be detected accurately with a simple configuration, and durability and reliability can be improved.

[Brief explanation of the drawing]

1 to 6 are diagrams showing a first embodiment of the displacement sensor according to the present invention, and FIG. 1 is a diagram showing a part of the sheet, and FIG.
Figure 3 is a load-resistance characteristic diagram of the stress-sensitive member, Figure 4 is an equivalent circuit diagram when the sheet in Figure 2 has no curved part, Figure 5 is an equivalent circuit diagram of Figure 2. A circuit diagram, FIG. 6 is a displacement-voltage characteristic diagram thereof, FIG. 7 is a configuration diagram showing a second embodiment of the displacement sensor according to the present invention, and FIGS. 8 and 9 are diagrams showing a conventional displacement sensor. FIG. 8 is a perspective view of a displacement sensor that utilizes the strain, and FIG. 9 is a perspective view of a displacement sensor that utilizes the winding resistance. 20... Sheet, 21... Copper foil (conductive member), 22...
・Pressure sensitive rubber (stress sensitive member), 23...Resistor film (resistor member), 25...DC power supply (
voltage applying means), 26... voltmeter (voltage detecting means).

Claims (1)

[Claims] A sheet having a three-layer structure with a stress-sensitive member in the center and conductive members and resistor members arranged on both sides thereof, a voltage applying means for applying a predetermined voltage to both ends of the resistor member of the sheet, and an end portion of the sheet. voltage detection means for detecting the voltage generated between the resistor member and the conductive member in the sheet, and when stress is applied to a predetermined point on the resistor side of the sheet, the conductivity of the stress-sensitive member of the sheet changes. A displacement sensor characterized in that the voltage detected by the voltage detection means changes depending on the stress generation point of the sheet.