JP2516747B2 - Ultrasonic temperature / pressure sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a temperature or pressure sensor, and particularly to an ultrasonic wave temperature / pressure suitable for measuring the temperature or pressure in a living body by using ultrasonic waves as a signal transmission medium. Regarding sensors.

(Prior Art) In recent years, in order to measure the temperature or pressure of each part in the living body for the purpose of biology, medical research or cancer treatment in particular, a non-power source sensor embedded in the living body for a long time and measurement in vitro. A method has been proposed in which measurement is performed without a wired connection to the instrument.

As the temperature measurement or pressure measurement method as described above, an antenna
A sensor in which a crystal oscillator and an ultrasonic transducer are connected to a coil is surgically implanted at a desired position in the living body, and electromagnetic energy of a required frequency is irradiated from outside the living body to oscillate the energy through the antenna coil. There is a method of observing the ultrasonic wave generated from the outside of the body by controlling the ultrasonic transducer with the electric current given to the child when the vibrator resonates with it (see Japanese Patent Application No. 60-021542). A temperature or pressure sensor and a pickup device for detecting ultrasonic waves emitted from the sensor from outside the body are generally shown in FIG. 2 (a).

That is, in the figure, X is a crystal oscillator having a series resonance point in the vicinity of 8 MHz, and an antenna coil L ₁ and an ultrasonic transducer SW are connected to form a closed loop with the crystal oscillator and embedded as a sensor in a required part in the living body. Along with the sensor, an antenna coil L ₂ is located on the surface of the living body, and a transmitter comprising a variable frequency oscillator 1 and a frequency meter 2 for generating an electromagnetic wave near 8 MHz, an ultrasonic microphone 3, a high frequency amplifier 4, and a level meter. A measuring system is composed of a receiving unit composed of 6 or the like.

In the measurement, the output of the variable frequency oscillator 1 is applied to the above-mentioned sensor via the antenna coil L ₂ connected thereto, and the ultrasonic wave oscillated by the sensor is received by the microphone 3 and the electric signal thereof is sent to the high-frequency amplifier 4. At the point where the oscillation frequency of the variable frequency oscillator 1 is changed while being amplified to a required level and then monitored by the level meter 6, the resonance frequency of the crystal oscillator of the sensor is detected at the point where the reading of the level meter becomes maximum. It is possible (see FIG. 2 (c)).

Therefore, if the relationship between the resonance frequency of the crystal unit X incorporated in the above-described sensor and the temperature or pressure is known, the temperature or pressure in the living body can be accurately measured.

Further, the structure of the in-vivo implantable sensor used for such measurement has been generally the one shown in FIG. 2 (b).

However, since the sensor having such a configuration uses a small antenna coil, it is difficult to increase the receiving sensitivity thereof, and there is a defect that the number of components is large and the sensor cannot be miniaturized.

Furthermore, since it uses electromagnetic waves, it often causes adverse effects and interference with other electronic devices.

(Object of the Invention) The present invention has been made in order to eliminate the defects of the conventional ultrasonic sensor as described above, and has the function of changing the resonance frequency by temperature or pressure and the function of the ultrasonic transducer. It is an object of the present invention to provide a piezoelectric or mechanical oscillator that can also serve as a piezoelectric element.

(Summary of the Invention) Since a mechanical oscillator represented by a conventional crystal oscillator has a resonance sharpness Q value as large as possible, it is necessary to reduce leakage of acoustic energy from a support portion, which is a main cause of deterioration of the Q value. While it was common to select the part with the smallest vibration displacement as the support part, the vibrator according to the present invention transmits and receives ultrasonic waves by transmitting a part of its acoustic energy to the container through the support part. It was designed to do.

(Examples of the Invention) The present invention will be described in detail below based on illustrated examples. FIG. 1A is a structural diagram of a sensor showing an embodiment of the present invention. In the figure, the ratio H / D between the base height (H) and the base bottom portion (D) of the tuning fork type crystal unit 7 is set to about 3 or less. By doing so, a part of the acoustic energy can be transmitted to the container 9 via the holding portion 8 of the vibrator 7.

FIG. 2B is a diagram of the experimental results showing the relationship between the H / D and the leakage energy, and a required excitation electrode is electrically provided on the vibrator 7 of the sensor shown in FIG. 1A. Excitation was performed and the acoustic leakage energy was measured with a microphone.

From the above experimental results, the sensor configured as shown in FIG. 1 (a) excites the vibrator 7 by applying ultrasonic energy from the outside, transmits the acoustic energy to the container 9, and holds the container 8 or the container. It will be appreciated that it is possible to re-emit the ultrasonic waves via 9, in which case the transducer 7 does not require electrodes.

In addition, in the above-described embodiment, the case where no electrode is attached to the vibrator 7 is shown, but it is also possible to attach an electrode to the vibrator.
As shown in the figure, if the antenna coils are connected in series so as to form a closed loop by attaching electrodes to the vibrator, a high frequency current is generated in the antenna coil by applying electromagnetic energy from the outside, and the electric signal thereof is It is possible to apply the vibration to the electrode to excite the vibrator, leak the vibration of the vibrator to the holding portion or the container, and receive the ultrasonic energy by the microphone and take it out.

FIG. 3 is an application of the ultrasonic leak type sensor 10 in which the measuring system of FIG. 2 is used as it is, and only the sensor is a vibrator 7 shown in FIG.

By doing so, the ultrasonic transducer and the temperature sensor are integrated and the size can be reduced, which is particularly suitable for an implantable sensor for measuring the temperature in the living body.

Further, when the vibrator 7 is used as a simple mechanical vibrator without attaching an electrode, ultrasonic waves are radiated from the ultrasonic transducer 11 for both transmission and reception to the sensor 12 as shown in FIG. If it substantially matches the resonance frequency of, the ultrasonic energy that is strongly re-radiated is caught by the ultrasonic transducer 11 for both transmission and reception, and the level meter 16 passes it through the gate circuit 13, the RF amplifier 14, and the filter 15. Measure the strength, adjust the variable frequency oscillator 17 so that the strength is maximized, and adjust the frequency counter.
Measure the frequency at 18.

The output of the variable frequency oscillator 17 is applied to the transmitting / receiving ultrasonic transducer 11 through another gate circuit 19 to change the oscillation frequency thereof, so that the temperature of the temperature sensor 12 can be changed from the value of the frequency counter 18 to a certain temperature. Since the resonance frequency can be known, its temperature can be known.

Reference numeral 20 is a control circuit for intermittently opening and closing the output of the variable frequency oscillator 17 by opening and closing the gate circuit 19 and controlling the gate circuit 13 so that the output is not directly input to the RF amplifier 14. .

Although only the tuning fork type crystal oscillator has been described above as the oscillator of the sensor, the present invention can use oscillators of other types.

For example, as shown in FIG. 5, a longitudinal vibrating crystal oscillator 21 is used, and the equivalent length l of the support portion 22 integrally extending from both nodes of the oscillator 21 is selected so as not to be λ / 4. By slightly breaking the left and right balance including 22, the required vibration energy can be emitted from the container 9 via the holding portion 8.

The shape of the ultrasonic wave receiving surface of the container 9 is shown in FIG. 6 (a).
Alternatively, the divergence of the ultrasonic beam can be controlled by forming the convex 23 lens shape or the concave 24 lens as in (b).

Although the case where the sensor according to the present invention is used as a temperature sensor has been described above, the present invention is not limited to this, and the container is replaced with a bellows or a diaphragm, and a vibrator having a double-supported structure is used. Then, it can be used as a pressure sensor.

(Advantages of the Invention) Since the present invention is configured as described above, the crystal unit having temperature or pressure information simultaneously has the function of an ultrasonic transducer, so that the sensor can be miniaturized. Especially when it is applied to a measurement system that receives and transmits ultrasonic waves, it does not require a small antenna coil, resulting in good sensitivity. When using this as an in-vivo temperature / pressure sensor, the sensor container is made of titanium or the like. Hyperthermia of cancer because it can be used for a long time without the problem of deterioration of characteristics due to penetration of body fluid compared to the conventional sensor which needs to be formed only with biocompatible metal and needs to wrap the antenna coil part with plastic etc. It exhibits a remarkable effect when used in temperature measurement systems such as.

[Brief description of drawings]

FIG. 1 (a) is a sectional view showing an embodiment of the sensor according to the present invention, FIG. 1 (b) is a diagram showing experimental results showing the degree of energy leakage, and FIG. 2 (a) is a conventional temperature measurement. FIG. 3B is a block diagram showing the configuration of the system, FIG. 2B is a schematic diagram showing the configuration of the sensor, FIG. 3C is a diagram showing the resonance characteristics of the sensor, and FIGS. 3 and 4 are sensors according to the present invention. FIG. 5 is a block diagram showing an embodiment of different temperature measurement systems utilizing the same, FIG. 5 is a sectional view showing another embodiment of the sensor according to the present invention, and FIGS. It is an external view which shows a different Example of the sensor container which concerns on invention. 7,21 …… Piezoelectric or mechanical oscillator, 9 …… Sealed container, 23,24 ……
Lenticular cross section.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area A61B 8/08 A61B 8/08 G01K 1/02 G01K 1/02 Z 7/32 7/32 D G01L 1/10 G01L 1/10 A 11/04 11/00 C

Claims (4)

(57) [Claims] 1. A piezoelectric or mechanical oscillator whose resonance frequency changes in response to temperature or pressure fluctuations is enclosed in a sealed container, and a part of mechanical vibration energy of the piezoelectric or mechanical oscillator is propagated to the sealed container. An ultrasonic temperature / pressure sensor characterized in that ultrasonic vibration can be transmitted and received through the hermetically sealed container. 2. A piezoelectric vibrator, the resonance frequency of which changes in response to a change in temperature or pressure, is provided with an electrode, and the ratio H / D of the base height (H) and the base bottom portion (D) of the piezoelectric vibrator is 3. The following tuning fork type vibrator is caused to propagate a part of the vibration energy of the vibrator to the hermetically-sealed container by enclosing the tuning-fork-type vibrator in a state where the bottom part thereof is in contact with the holding part, An ultrasonic temperature / pressure sensor characterized by enabling transmission and reception of ultrasonic vibrations. 3. A hermetically sealed container in which a part of a support portion integrally extending from both nodes of a longitudinally vibrating crystal unit whose resonance frequency changes in accordance with a change in temperature or pressure is in contact with a holding portion. By so doing, the equivalent length l of the supporting portion is selected so as not to be λ / 4 so that a part of the vibration energy of the vibrator is propagated to the sealed container, and ultrasonic vibration is transmitted and received through the sealed container. Ultrasonic temperature / pressure sensor characterized by enabling 4. An ultrasonic temperature according to claim 1, wherein one end surface of the piezoelectric or mechanical oscillator enclosure has a lens-shaped cross section. / Pressure sensor.