JPH0136564B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a torsion (rotation angle) system that detects torsion or rotation angle by utilizing the fact that when torsion (rotation angle) is applied to a mechanical vibrator, its resonance frequency changes. This relates to frequency converters. For more details,
The present invention relates to a torsion-frequency converter that can measure torque and angular acceleration with high precision.

Conventionally, accelerometers and angular accelerometers that utilize the phenomenon that when a beam with a rectangular cross section is twisted changes its section modulus, which changes the resonant frequency of the beam, have been proposed, for example, in U.S. Pat. No. 3197753,
It is publicly known from No. 3181373 and the like. However, these devices have a complex overall configuration, as they require a rectangular cross-section beam as a torsion detection means, a cross flexure structure and a separate diaphragm to support the rotating part, and a flexure separate from the beam to take on torque. It had become a thing.

Here, the present invention aims to realize a torsion-frequency converter having a simple overall configuration and high detection sensitivity.

The device according to the present invention does not utilize the principle that when a beam is twisted, its section modulus changes and the resonant frequency changes, but the device uses the torsion applied to a mechanical vibrator to
The feature is that it is converted into compressive axial force and extracted as a frequency change.

FIG. 1 is a perspective view showing an example of a device according to the present invention. In the figure, reference numeral 1 denotes a mechanical vibrator which is provided with a torsion (rotation angle θ) to be detected at one end and fixed at the other end, and is constructed symmetrically with respect to the central axis Cl. This mechanical vibrator 1 includes a central beam 11, outer beams 12 and 13 installed in parallel on both sides of the central beam 11, and coupling pieces 14 and 15 that connect the respective ends of these beams. I have it too. Here, the outer beams 12 and 13 serve to convert the applied torsion (rotation angle) into compressive axial force. Each coupling piece 14, 15 has a mounting hole 16,
17 are provided, and the central beam 11 is here attached to the connecting pieces 14, 15 via two supporting flexures 18 and 19. This support flexure constitutes an isolation means for preventing resonance vibration energy from leaking from both ends of the central beam 11 to one side of the coupling. Such a mechanical vibrator 1 is manufactured, for example, by cutting out a single plate-shaped material, or by etching a crystal plate or the like. Reference numerals 2 and 3 denote excitation means and vibration detection means for the central beam 11, which are attached to the front and back sides of the central beam 11, and PZT, for example, is used as these means. 4
is an oscillation circuit, which is coupled to the excitation means 2 and the vibration detection means 3, and constitutes a self-oscillation circuit that vibrates the mechanical vibrator 1 at its resonant frequency. 5 is a counter that counts the resonance frequency of the mechanical vibrator 1; 6 is an arithmetic circuit that inputs the signal from the counter 5; for example, a microprocessor is used. 7 is an indicator that displays the calculation results.

2 and 3 are explanatory views for explaining the operation of the mechanical vibrator shown in FIG. 1. FIG.

Now, in FIG. 2, if one end (lower side) of the mechanical vibrator 1 is fixed and the other end (upper side) is twisted by an angle θ, the outer beam portion will be twisted and shortened. Therefore, a compressive axial force is generated in the central beam portion.
In FIG. 3, the central beam 11 is transversely vibrating at a resonant frequency due to a self-oscillation oscillation loop composed of an excitation means 2, a vibration detection means 3, and an oscillation circuit 4. When the compressive axial force T is applied, this resonance frequency changes corresponding to the compressive axial force T, that is, the torsion angle θ. Therefore, by detecting this change in the resonance frequency using the counter 5 and performing a predetermined calculation, the twist angle θ can be determined.

Next, the operation when the dimensions of the mechanical vibrator 1 are determined as shown in FIG. 3 will be explained in more detail using mathematical formulas.

In FIG. 2, when the outer beams 12 and 13 are twisted by an angle θ, the lengths of the outer beams 12 and 13 become shorter, but this shrinkage amount δ
can be approximately expressed by equation (1).

δ≒L(1−cosθ′) (1) However, L: Length of central beam to connecting piece θ'=d/2L・θ (inclination angle of outer beams 12 and 13) d: Width of mechanical vibrator Furthermore, strain can be expressed by equation (2).

ε=-δ/L=1-cos θ'=-2sin ² θ'/2 (2) Here, if the tensile rigidity of the central beam 11 is K ₀ ' and the tensile rigidity of the flexure parts 18 and 19 is K ₁ , then
Of the strain ε expressed by equation (2), the portion ₀ generated in the central beam 11 can be expressed by equation (3).

ε ₀ =K ₁ /K ₀ +K ₁ =−2K ₁ /K ₀ +K ₁ sin ² θ′/2 (3) When such a strain ε occurs in the central beam 11,
This is equivalent to applying a compressive axial force T as shown in equation (4) to the central beam 11.

T=b・h・E・ε ₀ (4) Where, b: Width of the central beam 11 h: Thickness of the central beam 11 E: Longitudinal elastic modulus of the central beam 11 Fundamental mode of the central beam 11 with both ends fixed The resonance frequency f and the axial force T have a relationship as shown in equation (5).

f=f ₀ (1+KT) ^1/2 ≒ f ₀ (1+1/2KT) (5) However, f ₀ : Resonance frequency when T=O, K=l ² /4π ² IE l: Flexure of central beam 11 Length I: Second moment of area about the main axis perpendicular to the vibration direction (3), Equations (4) to (5) are as shown in Equation (6).

f=f ₀ {1-b・h・^l2 /2・4π ²・I・2K ₁ /(K ₀ +K
₁ )・sin ² θ′/2}=f ₀ {1-3/π ²・(l/h) ²
・K ₁ /(K ₀ +K ₁ )・sin ² d/4L・θ}(6) As is clear from equation (6), the resonant frequency f of the fundamental mode of the central beam 11 depends on the given rotation angle θ. It changes accordingly, and the angle θ can be determined from this resonance frequency f.

FIG. 4 is a diagram showing the relationship between torsion angle θ and resonance frequency change in the mechanical vibrator having the configuration shown in FIG. 1, with calculated values shown as solid lines and measured values shown as broken lines.

As is clear from FIG. 4, the measured values are in good agreement with the calculated values, and when θ=10° or more, the angle θ and the frequency change are almost linear, and the slope becomes large. Furthermore, the frequency change is reversed depending on the direction of twisting. Therefore, mechanical oscillator 1
By making it in a twisted state in advance and always using it with θ=10° or more, it is possible to realize a torsion-frequency converter with high detection sensitivity and the ability to determine the direction of twist.

According to the converter according to the present invention, the central beam, the flexure portion that supports the central beam, and the outer beam for applying axial force to the central beam can be configured in a plate-like integral structure, so that the configuration is simple. Moreover, a torsional frequency converter with high detection sensitivity can be realized.

FIGS. 5 and 6 are configuration diagrams showing other embodiments of the present invention.

In the embodiment shown in FIG. 5, the supporting flexure parts 18 and 19 supported on the central beam 11 have a single structure. The length and width of the supporting flexure portions 18, 19 are determined so that leakage of the resonant vibration energy of the central beam 11 from the terminals is minimized. Now, if we weaken the torsional rigidity of this flexure part,
Almost no torsion (rotation angle) occurs in the central beam, and it is possible to eliminate changes in the resonance frequency caused by twisting the central beam. That is, the resonant frequency of the center beam changes only by the compressive axial force generated in the center beam when the mechanical vibrator 1 is twisted, and the sensitivity can be increased.

The embodiment of FIG. 6 has depressions 12a, 13 near the center of the outer beams 12, 13 in the embodiment of FIG.
A is provided to adjust the torsional rigidity of the outer beams 12 and 13.

FIG. 7 and FIG. 8 are configuration diagrams showing an example of application of the mechanical vibrator according to the present invention.

The device shown in FIG. 7 is a torque meter configured by fixing one end of the mechanical vibrator 1 to the base 8 with a screw 80 and applying rotational torque to the other end.

In the principle model shown in FIG. 8, one end of the mechanical vibrator 1 is fixed to a shaft 90 to which an angular acceleration θ is applied, and a weight 92 that provides rotational inertia supported by an arm 91 is attached to the other end. This is an accelerometer. The shaft 90 is rotatably supported by a bearing 9, and the angular acceleration θ applied thereto is applied to one end of the mechanical vibrator 1, to which the arm 91 is attached, as a torsion corresponding to the angular acceleration θ. It's becoming like that.

In each of the above embodiments, it is assumed that the excitation means for exciting the central beam 11 and the vibration detection means for detecting the vibrations are coated with PZT. If the mechanical vibrator is made of a piezoelectric material such as crystal, an electromagnetic means may be used, and if the mechanical vibrator is made of a piezoelectric material such as crystal, electrodes may be attached to the mechanical vibrator to provide an excitation means and a vibration detection means. may be configured.

As described above, according to the present invention, a torsion-frequency converter having a simple overall configuration and high detection sensitivity can be realized.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the configuration of an example of the device according to the present invention, FIGS. 2 and 3 are explanatory diagrams of operation, and FIG. 4 is a line showing the relationship between torsion angle and frequency change in the device shown in FIG. 1. 5 and 6 are block diagrams showing other embodiments of the present invention, and FIGS. 7 and 8 are block diagrams showing application examples of the mechanical vibrator according to the present invention. 1... Mechanical vibrator, 11... Central beam, 12,1
3... Outer beam, 14, 15... Joining piece, 16, 1
7...Mounting hole, 18, 19...Support flexure,
2... Excitation means, 3... Vibration detection means, 4... Oscillation circuit, 5... Counter, 6... Arithmetic unit, 7...
Display.

Claims (1)

[Scope of Claims] 1. A central beam, outer beams installed in parallel on both sides of the central beam, a mechanical vibrator having coupling pieces that connect the respective ends of these beams, and vibrating the central beam. vibration detection means for detecting the vibration of the central beam, fixing one end of the mechanical vibrator and applying torsion to be converted to the other end so as to rotate about the central axis of the mechanical vibrator. Therefore, a self-excited oscillation loop including a torsion imparting means for applying a compressive axial force to the central beam, the vibration detection means, and an excitation means is provided, and a change in the resonant frequency of the central beam obtained from the self-excited oscillation loop is provided. A torsion-frequency converter that allows you to know the torsion (rotation angle). 2. The torsion-frequency converter according to claim 1, wherein both ends of the central beam are connected to the coupling pieces via flexures. 3. The torsion-frequency converter according to claim 1, wherein the other end of the mechanical vibrator is twisted by a certain rotation angle in advance.