JPS608722B2 - Feeler of minute displacement detector - Google Patents

Description

[Detailed description of the invention] The present invention relates to a feeler for a minute displacement detector.

Conventionally, there are various devices for extracting electrical signals in response to minute mechanical displacements, among which a movable electrode is arranged between a pair of fixed electrodes to form a pair of variable capacitors.
There is a device that combines these variable capacitors with oscillators and extracts the difference in the output frequencies of the two oscillators (Japanese Patent Laid-Open No. 5
3-50766). In this case, it is important that the capacitance change of the variable capacitor corresponds to the target mechanical displacement, and appropriately establishing this correspondence is the key to maximizing the displacement detection range.

The present invention has been made in view of these points, and an object of the present invention is to provide a feeler for a minute displacement detector that operates so that a change in the capacitance of a variable capacitor appropriately corresponds to a target mechanical displacement. do.

To achieve this objective, the present invention includes a rigid lever that contacts an object and pivots in accordance with the mechanical displacement of the object, and a rigid lever that has one end fixed to the rigid lever so that the end can move only in the longitudinal direction. an elastic beam that is supported by the lever and moves in a curved manner in response to the pivoting of the lever, and a pair of fixed electrodes that are provided to sandwich the elastic beam, and a pair of variable This is a feeler that converts a small mechanical displacement into an electrical change by changing the capacitance of a capacitor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A displacement detector to which the present invention is applied will be described below with reference to the accompanying drawings, and then an embodiment of the present invention will be described.

FIG. 1 shows the basic configuration of the present invention, in which Ev is a movable electrode, which cooperates with a pair of fixed electrodes Ef, Ef2 arranged in parallel to sandwich this movable electrode Ev. constitute variable capacitors C, , C2. The pair of variable capacitors C, C2 operate in opposite directions. That is,
When the movable electrode Ev swings in the direction of the arrow shown in the figure, the capacitance of one capacitor C decreases, and the capacitance of the other capacitor C2 decreases.
capacity increases. The increase or decrease in this capacitance is determined by the movable electrode Ev
and fixed electrode Ef. , Ef2. These pair of capacitors C, , C2 are connected in series with crystal oscillators xtal, , Xta12, respectively, and connected to oscillators OSC, , OSC2.

The crystal oscillators xtaL and XNE 12 may be connected in parallel with the oscillator, or these oscillators may be omitted.
The purpose of using a crystal resonator is to stabilize the oscillation frequency. The respective outputs of the oscillators OSC, OSC2 are both given to the mixer MIX, and the difference frequency signal F between the two is output from the output terminal.
d is taken out. Figures 2a and b are the movable electrodes Ev in Figure 1.
2 shows the change characteristics of the output frequencies f, etc. of each oscillator OSC, OSC2, etc. with respect to the stroke d.

That is, as the movable electrode Ev moves away from one fixed electrode Ef and approaches Ef2, the capacitor C gradually decreases and becomes C2.
increases gradually, and accordingly, the output frequencies of the oscillators OSC, . . . OSC2 also gradually increase and decrease. Figure 3 a and b are Nagoiki MI
It is an operating characteristic diagram of X, and two oscillators OSC, ,OSC
This figure shows the operation of extracting the difference between the two outputs f, , f2.

That is, although the characteristics f, and f2 shown in FIGS. 2a and b are both nonlinear, they are symmetrical to each other, so f. When ~f2 is determined, as shown in FIG. 3b, the central part is approximately straight and both ends are gently curved to form an S-shape. Therefore, by using the linear range K centered on the point p of this characteristic, it is possible to extract a frequency output that changes linearly in accordance with the stroke of the movable electrode. FIG. 4 shows an embodiment of the present invention, in which one end is pivoted so as to pivot around a fulcrum 2, and the other end pivots in response to the mechanical displacement of the object. It is a rigid lever.

An elastic beam Ev is connected to one end of this rigid lever.
is provided. The elastic beam Ev has one end fixed to the rigid beam and pivots in response to the pivoting of the rigid lever 1, while the other end is supported by a support member 3 that allows only longitudinal movement of the elastic beam Ev. There is. Support member 3
Alternatively, a wire stretched in a cross or Y shape in a direction perpendicular to the longitudinal direction of the elastic beam Ev may be used, or a guide member that can perform an equivalent function may be used. Fixed electrodes Ef, .Ef2 are provided to sandwich the elastic beam Ev, forming a pair of capacitors C, .C2 with the elastic beam Ev as a movable electrode. In this embodiment, when the rigid lever 1 pivots in response to the mechanical displacement of the object, the elastic beam Ev bends as shown by the dash-dotted line. The degree of this bending corresponds to the amount of pivoting of the rigid lever l, that is, the mechanical displacement of the object. At this time, the elastic beam Ev pulls up the joint portion with the support member 3 upward in the figure in accordance with its bending. The support member 3 allows movement of the elastic beam Ev in the longitudinal direction, but does not allow movement in a direction perpendicular to the longitudinal direction. Therefore, the degree of curvature of the elastic beam Ev always becomes an arc corresponding to the mechanical displacement of the object. Here, if no bending stress is generated in Ev, or if the stress is close to this state and the stress is small, Ev will easily respond to the displacement of the feeler at the tip, but Ev has already been bent considerably and stress occurs to a considerable extent, the stiffness of the beam itself is
Since the strain stress increases, the degree of response of Ev to the displacement of the feeler at the tip becomes smaller than in the above state.

Comparing this with the case where the end of the elastic beam is not supported at all, the response range of the elastic beam Ev to the amount of mechanical displacement of the object is expanded.

That is, if the other end of the elastic beam Ev is a free end, the amount of pivoting of the rigid lever and the amount of response of the elastic beam Ev are 1:1.
However, if the other end of the elastic beam Ev is connected to the support member, the displacement of the other end of the elastic beam Ev is restrained,
The amount of response of the elastic beam Ev is smaller than the amount of pivoting of the rigid lever 1. This makes it possible to make the curve of the f, , f2 characteristics in FIG. 3a a gentler curvature, and to widen the straight line area K as shown by the two-dot chain line in FIG. 3b. Fifth
The figure shows another processing method for the outputs of the oscillators OSC, . That is, two oscillators OSC,
, OSC2 is received by the receiver RCV and given to the mixers MIX, , MIX2 separately to obtain the local oscillation frequency U○, .
Frequency conversion is performed by mixing with L02. The two signals after frequency conversion are mixed in a mixer MIX3 to obtain a measurement signal fa. This fa can be handled in the same way as f and -f2 in the circuit of FIG. With this configuration, the following difficulties can be solved. One of the difficulties is that the oscillators OSC, ,OSC
When the output frequency difference of 2 is several K ratio, the signal interval is 0.2 to 0.
3 milliseconds, making it impossible to follow a rotating body. Second, the output frequency of the oscillators OSC, OSC2 is most easily obtained when a crystal oscillator is used. The frequency is too high when applied to a frequency-to-voltage converter to form a voltage signal. As a result of the frequency conversion, the signal interval becomes on the order of microseconds, and a measurement signal with good responsiveness and easy handling is obtained without the signal change of several KHz being buried in the error range. As described above, the present invention transmits the mechanical displacement of the object to the elastic beam via the Okayama body lever, and furthermore, the mechanical displacement of the object is transmitted to the elastic beam through the Okayama body lever. Since the end of the elastic beam opposite to the Okayama body lever is configured to be able to move only in the longitudinal direction, the feeler of the minute displacement detector can respond to the mechanical displacement of the object and can respond to a wide range of displacements. can be provided.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the basic configuration of the present invention, Figure 2 is a block diagram showing the basic configuration of the present invention.
Figures a, b and Figures 3 a and b are characteristic diagrams showing the operation of the device in Figure 1, Figure 4 is an explanatory diagram showing an embodiment of the present invention, and Figure 5 is the output of the oscillator in Figure 1. The figure which shows the other processing method of. Ev: movable electrode, Ef: fixed electrode, OSC: oscillator, MIX: mixer,
C: variable capacitor, 1: rigid beam, 2: fulcrum, 3: support member.
Crocodile l map Z diagram multiple 3 diagrams 4 diagrams multiple 5 diagrams

Claims (1)

[Claims] 1 A rigid lever that contacts an object and pivots according to the mechanical displacement of the object; one end is fixed to the rigid lever and the other end is supported so as to be movable only in the longitudinal direction, and the pivoting of the lever It is equipped with an elastic beam that bends in response to the mechanical displacement of the target object, and a pair of fixed electrodes that are provided to sandwich the elastic beam and form a pair of variable capacitors in cooperation with the elastic beam. The feeler of the minute displacement detector is configured to extract an electrical change corresponding to a minute mechanical displacement by a change in the capacitance of the variable capacitor.