JPH06323927A - Structure of temperature sensor using ultrasonic waves as temperature information transmission medium - Google Patents

Abstract

PURPOSE:To adjust the degree of the acoustic coupling between a base and a vibrating body without restricting the shape of a tuning fork-type vibrating body by a method wherein a slit is cut on the surface of the base and the interval between the bottom part of a tuning fork and the surface of the base is set to a desired value when the tuning fork is inserted into, and fixed to, the slit. CONSTITUTION:The ratio L/W of the length L of the base part of a tuning fork to the width W of a finger has an optimum value according to the acoustic impedance of an object, to be measured, on which a sensor is left or to which the sensor is fixed. In addition, when the length L of the base part becomes extremely short, the mechanical strength of the base part causes a problem. Then, a slit 5 which corresponds to the thickness of a tuning fork-type vibrating body 2 is cut on the surface of a base 1, and the tuning fork-type vibrating body 2 which is provided with a base part having a sufficient length L' is inserted into the slit and fixed by an adhesive. Then, according to the degree of its insertion, the acoustic coupling between the tuning fork-type vibrating body 2 and the base 1 can be set to a value which is suitable for a use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a wireless temperature sensor using ultrasonic waves as a temperature information transmission medium.

[0002]

2. Description of the Related Art The inventor of the present application has conventionally used an ultrasonic signal from outside to an electrodeless vibrating body sealed in a suitable capsule as a method of measuring the temperature in a container or in a living body wirelessly and without power supply. The vibration body excited by this continues vibration for a while even if the irradiation of the ultrasonic signal is interrupted, and the vibration frequency is the resonance frequency corresponding to the temperature around the vibration body. A system has been established to detect the temperature around the vibrating body by utilizing the fact that the vibration energy due to the resonance frequency is radiated as ultrasonic waves through the capsule (Japanese Patent Application No. 61-211888 / Japanese Patent Laid-Open No. 63-1988). 66427).

As shown in FIG. 2, the sensor used in the system as described above is a vibration of a piezoelectric material such as quartz or quartz, sapphire single crystal, or a metal having a small expansion coefficient such as Inconel on one end face of the metal base 1. The body 2 is fixed, covered with a cap 4, and hermetically sealed with the base 1.

The above-mentioned sensor transmits ultrasonic waves to the built-in vibrating body via the base and causes the vibration energy of the vibrating body to be radiated to the outside as ultrasonic waves via the base. It is necessary to properly select the degree of acoustic coupling with the base in accordance with the acoustic impedance of the DUT, but even if the shape of the vibrating body is the tuning fork type most suitable for the above requirements, the degree of acoustic coupling should be set to an appropriate value. There is a problem in that the shape of the vibrating body is restricted in setting.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the drawbacks of the conventional wireless temperature sensor utilizing ultrasonic waves as described above, and specially limits the shape of the tuning fork type vibrator incorporated in the sensor. An object of the present invention is to provide a wireless temperature sensor that uses an ultrasonic wave as a temperature information transmission medium that can adjust the degree of acoustic coupling between the base and the vibrating body without using the ultrasonic wave.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, a temperature sensor according to the present invention cuts a slit corresponding to the thickness of the base of a tuning fork on a base surface on which a tuning fork type vibrator is to be fixed, and the slit has a base of the tuning fork. When inserting and fixing, the gap between the bottom of the fork of the tuning fork and the surface of the base is set to a desired value.

[0007]

The present invention will be described in detail below with reference to the embodiments shown in the drawings.

FIG. 1 (a) is a view for explaining the parameters that influence the acoustic coupling between the base 1 of the temperature sensor according to the present invention and the tuning fork type vibrator 2 fixed to the base 1. This sensor is as described above. The vibrating body 2 receives excitation energy by ultrasonic waves through the base 1 that fixes the vibrating body 2, and emits ultrasonic waves having a resonance frequency corresponding to the environmental temperature where the vibrating body 2 is placed through the base. It is necessary that the vibrating body and the base are appropriately acoustically coupled, in other words, the vibration energy of the vibrating body should be appropriately leaked from the base.

From the above point of view, if the vibrating body utilizes bending vibration of a rod cantilevered on the base, the amount of vibration energy leaks from the supporting portion is large (that is, the Q of vibration is low), but it seems to be convenient. Has a defect that it is difficult to control the degree of acoustic coupling.

On the other hand, the tuning fork type vibrator is a vibrator having substantially no vibration energy leakage by adjusting the length L of the base of the tuning fork as shown in FIG. Used) to those that produce the required acoustic coupling.

According to the experiments conducted by the inventor of the present application, the ratio L / W of the length L of the base portion and the width W of the finger of the tuning fork is optimal depending on the acoustic impedance of the temperature-measured object on which the sensor is left or fixed. There is a value, for example, L / W ≈ 3 when this sensor is left or fixed on a hard object such as metal, and L / W when it is relatively soft such as resin. <3
When suspending with a thread in a fluid such as liquid or gas, L
It has been found that the transmission of vibration energy is good when / W <2.

Therefore, it is desirable to preset the value of L / W for each application, but when L / W is 3 or less, the length L of the vibrating body base becomes extremely small and the mechanical strength of the base becomes a problem.

Therefore, as shown in FIG. 1 (b), a tuning fork type vibrator having a slit 5 corresponding to the thickness of the vibrator 2 or 2'is cut on the surface of the base 1 and having a base having a sufficient length L '. By fixing by insertion (with the adhesive 3), the acoustic coupling between the vibrating body and the base can be set to a value suitable for the application depending on the degree of insertion.

[0014]

Since the present invention is configured as described above, it is possible to adjust the degree of acoustic coupling between the vibrating body of the sensor and the base fixing the vibrating body of the sensor by an extremely simple method. The sensitivity of the wireless temperature sensor used as the temperature information transmission medium is adapted to the property of the temperature-measuring object, and there is a remarkable effect in measuring the temperature with good sensitivity.

[Brief description of drawings]

1A is a diagram for explaining the principle of the present invention, and FIG. 1B is a sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a wireless temperature sensor utilizing ultrasonic waves, which has been studied conventionally.

[Explanation of symbols]

1 ... Base, 2 ... Tuning fork type vibrator, 4 ... Cap,
5: Slit

Claims (1)

[Claims] 1. An electrodeless vibrator which is excited by an ultrasonic wave signal from the outside and continues to vibrate at a resonance frequency corresponding to the ambient temperature for a while even if the transmission of the excitation signal is stopped is enclosed in a metal case. In a temperature sensor, a slit corresponding to the thickness of a tuning fork type vibration body base is provided on a vibration body fixing surface of a base forming a part of the metal case, and the base of the tuning fork type vibration body is inserted into the slit. While fixing
The degree of acoustic coupling between the vibrating body and the base can be adjusted to a desired value by appropriately adjusting the distance between the bottom of the fork of the tuning fork type vibrating body and the surface of the base. Structure of a temperature sensor using ultrasonic waves as a temperature information transmission medium.