JPH052256B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a load converter that converts a load into an electrical signal.

BACKGROUND ART Conventionally, load converters as shown in FIGS. 3 and 4 have been known.

Figure 3 shows a strain gauge 3 in a strain body 2 with a roberval mechanism made by drilling a hole 1 in a metal block.
A to 3d are pasted, and the strain gauges 3a to 3d are pasted.
3d is connected to a bridge circuit and the amount of displacement of the strain body 2 is detected by strain gauges 3a to 3d, thereby obtaining an output voltage according to the load G between the output terminals of this bridge circuit. In FIG. 3, 4 is the fixed side of the strain body 2, and 5 is the movable side of the strain body 2.

Figure 4 shows a load transducer using a mechanical vibrator 6 such as a crystal oscillator, tuning fork, or ceramic piezoelectric element. A load G is applied to the vibrator 6 through the oscillator 8, and the detection circuit 9 detects the amount of deviation Δ of the oscillation frequency of the feedback amplifier 7 due to the load G.
is detected by the detection circuit 9, and the detected deviation amount Δ of the detection circuit 9 is used as a load signal.

Problems to be Solved by the Invention In the conventional load transducer as shown in Fig. 3, a ram 8 or the like is used as in the case of Fig. 4 which uses a vibrator (usually with an oscillation frequency on the order of several kilohertz). Although it is possible to make a load transducer for large loads without any problems, it is difficult to obtain high resolution as in the case of FIG. 4 due to the effects of strain gauge adhesion. In a load transducer using a mechanical vibrator 6 as shown in Fig. 3, the vibrator 6 is the vibrating part.
Since the vibrator itself needs to support the load, it is necessary to increase the strength of the vibrator 6 in order to directly receive the large load. However, increasing the strength lowers the vibration (resonance) frequency and increases resolution. Furthermore, since the drive energy also increases, the oscillation circuit etc. becomes large-scale.On the other hand, in order to obtain high resolution, increasing the frequency reduces the strength and cannot directly receive large loads, so a complex ram system is required. becomes.

SUMMARY OF THE INVENTION An object of the present invention is to provide a load transducer that can directly receive a large load without using a lever or the like, and that can provide a resolution higher than that of a conventional crystal oscillator type load transducer.

Means for Solving the Problems The load converter of the present invention includes a cavity resonant housing whose internal cavity shape deforms in response to a load, and a coupler provided on the internal input side of the cavity resonant housing with a constant frequency. an oscillator that applies a burst wave, and a decay time measuring circuit that measures the time required for the output signal of the coupler provided on the internal output side of the cavity resonant housing to decay;
The present invention is characterized in that the output signal of the decay time measuring circuit is a weighed value signal corresponding to the load.

Effect According to this configuration, when a load is applied to the cavity resonant housing, its internal shape is deformed according to the load value,
The Q of the cavity resonant housing changes in accordance with this deformation.
When a burst wave, that is, a certain amount of energy is applied to the cavity resonator, the attenuation rate of the burst wave is Q
is inversely proportional to. Therefore, by measuring the attenuation rate (attenuation time) of the burst wave, it is possible to detect a change in Q, that is, a load value, and the attenuation time measuring circuit detects this change in Q and uses it as a weighted value signal.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 shows a vertical cross-sectional view of a sealed cavity resonant case 10 and its peripheral circuit. The cavity resonant housing 10 is placed on the fixed side 11,
The load G is supported via the cavity resonant housing 10. Hairpin coils 12 and 13 as couplers are provided at appropriate positions in the cavity resonant housing 10, and a burst wave F ₁ (FIG. 2a) generated by an oscillator 14 is applied to the coil 12. . coil 1
3 is connected to a decay time measuring circuit 15.

With this configuration, the cavity resonant housing 10 is not deformed in the unloaded state where no load G is applied, so the burst wave F ₁ applied to the coil 12 is transmitted to the coil 13 as shown in FIG. 2b. A damped wave F ₂ whose attenuation changes as follows is induced. Let t ₀ be the decay time of the damped wave F ₂ under no load.

When a load G acts, the part on which the load G acts elastically deforms inward as shown by the imaginary line _A in FIG. In this case, even if the same burst wave F ₁ is applied, the attenuated wave 1 shown in FIG. 3b is generated in the coil 13.
6 occurs, a time _{t 1} shorter than time t 0 is detected via the decay time measurement circuit 15, and the difference between times t ₀ and t ₁ is a function of the load G.

Therefore, by measuring the degree of change in the decay time of Δ via the decay time measurement circuit 15, the magnitude of the load G can be determined. Here, the cavity resonant housing 10 can be easily constructed to withstand a large load by processing a metal block in the same manner as the cell body 2 shown in FIG.

Furthermore, since the resonant frequency of the cavity resonant housing 10 having a practical size and shape is on the order of several hundred MHz to several GHz, the oscillation frequency of the oscillator 14 is set to the cavity resonant housing 10.
The resonant frequency can be on the order of several hundred MHz to several GHz, and the amount of change in the time _t1 relative to the amount of change in the load acting on the cavity resonant housing 10 is large. Therefore, higher resolution can be expected compared to conventional systems that use a crystal oscillator 6 and handle oscillation frequencies on the order of several KHz.

In addition, as a means for quantitatively measuring the internal shape change that the cavity resonant housing 10 undergoes due to the load G, the coils 12 and 13 are connected to a feedback amplifier 17 as shown in FIG.
The feedback amplifier 17 is oscillated at the resonant frequency of the cavity resonant case 10, and the detection circuit 18 detects the amount of deviation Δ of the oscillation frequency of the feedback amplifier 17 from the fundamental resonant frequency ₀ . Although it is possible to know the load G from _the amount of change in You can expect more stable load conversion than the configuration shown in the figure.

In each of the above embodiments, a coaxial type cavity resonant housing 10 is used as an example, but similar effects can be expected if the cavity resonant housing 10 has a resonant frequency that changes depending on the applied load.

Effects of the Invention As explained above, the load converter of the present invention supports a load with a cavity resonant housing, and uses a burst wave to measure the degree of elastic deformation of the cavity resonant housing whose cavity shape changes according to the load value. Since the oscillator that generates the oscillator and the decay time measurement circuit detect the change in Q of the cavity resonant housing, the cavity resonant housing can be made strong enough to withstand large loads, making it possible to use a ramrod like in the case of conventional crystal oscillation systems. Moreover, since the fundamental oscillation frequency is high, on the order of several hundred megahertz to several gigahertz, it is possible to obtain a weight value signal with higher resolution than the crystal oscillation method.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the load transducer of the present invention, Fig. 2 is an input/output waveform diagram of Fig. 1, Figs. 3 and 4 are block diagrams of conventional load transducers, respectively, and Fig. 5 is a diagram of the present invention. FIG. 2 is a configuration diagram for explaining the effectiveness of the invention. DESCRIPTION OF SYMBOLS 10... Cavity resonance housing, 12, 13... Hairpin coil [coupler], 14... Oscillator, 15... Decay time measurement circuit.

Claims (1)

[Claims] 1. A cavity resonant housing whose internal cavity shape deforms under load; an oscillator that applies a burst wave of a constant frequency to a coupler provided on the internal input side of the cavity resonant housing; A load converter that is provided with a decay time measurement circuit that measures the time required for decay of an output signal of a coupler provided on an internal output side, and uses an output signal of the decay time measurement circuit as a weighted value signal corresponding to the load.