JPH0333327B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to cardiocardiography, which measures minute vibrations on the body surface of the apex of the heart, neck, radius, etc., which occur as the heart and blood vessels expand and contract. Regarding converters.

[Summary of the Invention] The present invention provides a cardiogram transducer for measuring minute vibrations on the surface of a body, in which a magnetic field generating element is fixedly disposed within a shield case, and a strip-shaped amorphous ferromagnetic thin strip is placed at a distance from the magnetic field generating element. Place the obi,
A detection coil having the amorphous ferromagnetic ribbon as its magnetic core, a circuit for detecting its self-inductance, and a detection coil fixed to the end of the amorphous ferromagnetic ribbon near the magnetic field generating element and attached to the body surface. A sensing chip that is brought into contact with each other directly or via an intermediate member is provided, and changes in the magnetic field applied to the detection coil due to changes in the relative distance between the magnetic field generating element and the amorphous ferromagnetic ribbon are detected by the self-inductance of the coil. By converting and detecting changes in the body surface, minute vibrations on the body surface can be measured without applying pressure to the measurement site and without requiring special skill.

[Prior Art] Conventionally, in clinical diagnosis of heart or blood vessel diseases, in addition to electrocardiograms, apical pulsatograms, which measure vibrations of the chest wall based on myocardial activity, and jugular venous waves, which measure vascular pulsations, have been used. The cardiac diagram is used. This cardiocardiogram is said to be an effective means for diagnosing valvular heart disease, congenital heart disease, carotid artery stenosis, etc., which are difficult to diagnose with an electrocardiogram.

Conventionally, as a cardiogram transducer for detecting such minute displacements, for example, an air conduction microphone, an acceleration transducer using a piezoelectric element, or a Perrotte type pressure pulse wave transducer have been used. Among these, air conduction microphones convert body surface vibrations into sound pressure and detect them, and are also used as heartbeat microphones.

[Problems to be Solved by the Invention] However, in the case of an acceleration type transducer using an air conduction type microphone, such a conventional cardiocardiogram transducer cannot measure vibrations on the body surface. In order to do this, the microphone mounting opening had to be pressed against and in close contact with the measurement site on the body surface in an optimal manner, and its use required skill and had poor operability.

In addition, in the case of the Perotste type pressure pulse wave transducer that uses a piezoelectric element, it is easier to operate than the air conduction type, but it detects minute vibrations on the body surface because it presses the measurement site. The problem was that it was difficult to do so.

This invention aims to solve these problems.

[Means for solving the problem] Therefore, the cardiac diagnostic converter according to this invention has the following features:
A magnetic field generating element that is fixedly placed in a shield case and generates a constant magnetic field, a strip-shaped amorphous ferromagnetic thin strip that is placed in the shield case at a distance from the magnetic field generating element, and the amorphous ferromagnetic material. A detection coil whose magnetic core is a body ribbon;
A circuit that detects the self-inductance of the coil by flowing a constant minute alternating current through the coil, and a circuit that is fixed to the end of the amorphous ferromagnetic thin strip near the magnetic field generating element, and are attached directly to the body surface or attached to an intermediate member. and a sensing chip made of a non-magnetic material that is brought into contact with the magnetic field generating element through the amorphous ferromagnetic thin strip. The displacement of the body surface is detected by converting it into a change and detecting it.

[Operation] According to the cardiac converter configured in this way,
When the body surface is displaced, the amorphous ferromagnetic ribbon is displaced via the sensing chip that comes into contact with it.
When the relative distance between the magnetic field generating element and the amorphous ferromagnetic ribbon changes, the magnetic field applied by the magnetic field generating element to the coil whose magnetic core is the amorphous ferromagnetic ribbon changes, but this is caused by Displacement on the body surface is measured by converting it into a change in inductance and detecting it, so it can be detected with a minute current, which requires special skill to detect stable displacement without hysteresis loss. It can be operated with good operability.

[Example] Hereinafter, an example of the present invention will be described based on the accompanying drawings.

FIG. 1 is a schematic diagram showing an example of the present invention.

First, to explain its configuration, this cardiac diagram converter is fixedly arranged via a magnet installation stand 21 on the upper wall surface 1a of a shield case 1 made of permalloy (magnetic material), for example, and is exposed to a certain magnetic field. A small magnet 6, which is a magnetic field generating element that generates a
A detection coil 3 (hereinafter simply referred to as coil 3) is an inductance element whose magnetic core is the amorphous ferromagnetic thin strip 2, and a detection method in which a constant minute alternating current is passed through the coil 3 to detect its self-inductance. A non-magnetic material is fixed to the circuit 4 and the end 2a of the amorphous ferromagnetic thin ribbon 2 closer to the small magnet 6, for example with adhesive, and brings the lower end contact surface 20a into direct contact with the body surface 5. The sensing chip 20 converts changes in the magnetic field applied to the coil 3 due to changes in the relative distance between the small magnet 6 and the amorphous ferromagnetic ribbon 2 into changes in the self-inductance of the coil 3 and detects the changes. , minute displacements or vibrations of the body surface 5 in the direction of arrow A in FIG. 1 are measured.

The small magnet 6 is, for example, a Ba magnet with a diameter of 3 mm and a thickness of 1.5 mm.
- It is a disk-shaped magnet formed of a ferrite plastic magnet, and the amorphous ferromagnetic thin ribbon 2 is a high magnetic permeability material with zero magnetostriction and a coercive force Hc of about 0.02 oersteds at a frequency of 1 KHz, for example. As shown in FIG. 2, it has a rectangular shape with a width of 0.5 mm, a thickness of 30 μm, and a total length lr of 10 mm, and is attached to a backing film 8 made of, for example, a celluloid board with an adhesive.

Then, the amorphous ferromagnetic ribbon 2 is
For example, it is fitted into the vertical groove 9a of a coil installation base 9 formed of a non-magnetic material such as aluminum and is bonded together, and the horizontal groove 9 formed on the coil installation base 9
In b, as shown in Fig. 3, an amorphous ferromagnetic thin ribbon 2 is inserted into the inside, and a bobbin 7 on which a coil 3 is wound, for example, with a coil length of 4 mm and a number of turns N = 150, is inserted into the outer periphery. It is hardened and fixed with adhesive 11.

This coil installation stand 9 is fixedly installed with a locking groove 9c formed on the lower surface placed on the upper part of an annular pedestal 12, and the front end 2a of the amorphous ferromagnetic thin ribbon 2
The position shown in FIG. 1 is located approximately at the center opening of the pedestal 12, and is arranged to receive the applied magnetic field of the small magnet 6 most easily.

Moreover, both ends 3 of the coil 3 are placed on the pedestal 12.
A lead wire 13 is provided for connecting the wires a and 3b to the detection circuit 4 for detecting self-inductance, and the two conductor portions 13a and 13b are fixed on the pedestal 12, and one end is connected to the coil 3, respectively. Connection terminals 14a, 1 connected to both ends 3a, 3b
4b.

Then, the shield case 1 is placed from above so as to cover the amorphous ferromagnetic thin strip 2, the pedestal 12, etc., and the shield case 1 is made of the same magnetic material as the shield case 1 from the bottom side, and the outer periphery of the lower surface is covered with the shield case 1. A disk-shaped shield plate 15 to which an annular cover member 24 is attached with an adhesive or the like is fixed to magnetically shield the amorphous ferromagnetic ribbon 2 and the like inside.

The detection circuit 4 is located outside the shield case 1, and as shown in FIG.
A small alternating current for detection of about i=1mA is connected to the resistor 1.
A constant current AC power supply 17 that flows through the coil 3 via the
and a detection amplifier 1 that detects, amplifies and rectifies the voltage at the connection point between the resistor 16 and the coil 3, that is, the voltage V _L generated between both ends 3a and 3b of the coil 3.
8 and a filter 19 for smoothing the output of the coil 3.
Detect the self-inductance L of .

V _L =jωLi L=V _L /jωi Next, the operation of this embodiment configured as described above will be explained.

The self-inductance L of the coil 3 according to this embodiment is proportional to the magnetic permeability μ of the amorphous ferromagnetic ribbon 2 used as the magnetic core. When there is no external magnetic field, the magnetic permeability μ is given by the initial magnetic permeability μi, but when there is an external magnetic field, the magnetic permeability μ is the point on the magnetization curve that corresponds to the external magnetic field (hereinafter referred to as the operating point).
It is necessary to use the reversible magnetic permeability μrev at .

Since the reversible magnetic permeability μrev monotonically decreases as the external magnetic field increases, as the amorphous ferromagnetic ribbon 2 serving as the magnetic core approaches saturation, the reversible magnetic permeability μrev approaches 1 accordingly.

Therefore, when the amorphous ferromagnetic ribbon 2 approaches the small magnet 6, the self-inductance L of the coil 3 gradually decreases as shown in FIG. As the distance x decreases, the amorphous ferromagnetic ribbon 2 approaches saturation, and the self-inductance L of the coil 3 approaches the value of the inductance of the air core.

Furthermore, the magnetic field from the small magnet 6 increases rapidly as the distance x becomes smaller, but since the reversible magnetic permeability μrev of the magnetic core decreases as the magnetic core approaches saturation, the nonlinearity of the magnetic field is canceled out, and the distance x Since a region (linear detection region indicated by the width a in FIG. 5) in which the self-inductance L is proportional to the current value appears, minute vibrations on the body surface 5 can be measured by using this region.

FIG. 6 is a diagram showing the results of actually measuring the pulsation of the radial artery using the cardiogram converter according to the present invention.

During this measurement, the conversion diagram for the cardiac diagram should be
The sensing chip 20 is only brought into contact with the measurement site, and the weight of the transducer is only added to the circumference of the measurement site via the support member 24, so the sensing chip 20 only lightly contacts the measurement site. The measurement site on the body surface 5 is not compressed by the weight of the transducer, and pulsations on the body surface as shown in FIG. 6 can be faithfully and accurately detected.

As shown in FIG. 7, in this machine diagram converter, for example, when the small magnet 6 is fixed on the film 10 stretched over the opening 15a of the shield plate 15 forming the lower shield case, If the distance between the small magnet 6 and the bottom inner circumference 15b of the shield plate 15 is too short, the magnetic flux from the small magnet 6 will pass through the shield plate 15, so that the magnetic flux entering the amorphous ferromagnetic ribbon 2 will be relatively On the other hand, if the shield plate 15 is too far away, the shielding effect decreases and noise easily enters, so the size and positional relationship of the small magnet 6 and the shield plate 15 are restricted. Although there were some problems, the cardiac diagram converter according to the present invention has a small magnet 6 fixed to the upper wall surface 1a inside the shield case 1, so it is free from such restrictions and has good magnetic flux efficiency. Strong against noise.

FIG. 8 shows a sensing chip 20 mounted on the upper surface of the film 10 adhered to the backing member 24 on the lower surface of the shield plate.
Another embodiment is shown in which the lower end of is fixed, and parts corresponding to those in FIG. 1 are given the same reference numerals.

The film 10, which is an intermediate member, has a thickness of, for example,
It is a circular polyimide film with a diameter of 25 μm, and its circular outer circumferential portion is adhered to the backing member 24 attached to the outer circumferential portion of the lower surface of the shield plate 15 with an adhesive or the like, and stretched over the opening 15a, and the center of the polyimide film is At the top, one end is a front end portion 2 of an amorphous ferromagnetic thin ribbon 2.
The contact surface 20a on the lower end side of the sensing chip 20 fixed to the contact surface 20a is fixed by adhesive or the like.

In this way, the sensing chip 20 is not directly touched from the outside, so handling becomes easier.

Even with this structure, the vibration to be measured on the body surface 5 is as small as 10 μm, so the vibration can be faithfully detected as a change in self-inductance.

FIG. 9 shows a further different embodiment in which the film according to the embodiment shown in FIG. 8 is provided with a convex portion in contact with the body surface at the center, and parts corresponding to those in FIGS. 1 and 8 are designated by the same reference numerals. It is attached.

In this embodiment, a film 10' having a protrusion 10a formed in the center is bonded to the upper surface of the shield plate 15 with the outer circumference thereof with the protrusion 10a facing downward.
A sensing chip 20' is fixed to the back side of the convex portion 10a, and the lower surface of the convex portion 10a is adhered to the body surface 5. In this way, the length (height) of the sensing chip 20' can be shortened, and the amount of tilting of the sensing chip 20' relative to the film 10' can be reduced, so that assembly work can be facilitated.

It should be noted that the linear detection area and the detection sensitivity shown in FIG.
By shortening the total length lr (Fig. 2) of As a result, a large demagnetizing field is generated inside the amorphous ferromagnetic ribbon 2 in the opposite direction to the external magnetic field from the small magnet 6.
The linear detection area similarly moves toward the smaller distance x.

Furthermore, the linear detection area and detection sensitivity cannot be changed by changing the composition of the amorphous ferromagnetic ribbon, its annealing (heat treatment) method, the size of the small magnet, or even by applying a bias magnetic field. can.

As described above, in the cardiogram converter according to the present invention, the self-inductance of the coil is proportional to the magnetic permeability μ of the magnetic core material of the coil, and this permeability μ
Note that when an external magnetic field exists, is proportional to the reversible magnetic permeability μrev at the operating point on the AC magnetization curve, and the self-inductance of the detection coil according to this reversible magnetic permeability μrev can be expressed as By detecting each time, it is possible to measure changes in the external magnetic field, that is, minute displacements of the body surface that the sensing chip is in contact with, either directly or through a film.

Therefore, instead of passing a large alternating current through the coil and causing the magnetic flux fluctuations that would cause the magnetic core to swing to the saturation region on the magnetization curve as in the past, by passing a small alternating current, the magnetic core can be displaced in a non-saturated manner. By simply applying a small magnetic flux fluctuation within a linear detection region, the reversible magnetic permeability μrev at the operating point, that is, the self-inductance of the coil, can be detected from the voltage across both terminals of the coil.

Therefore, the alternating current flowing through the inductance detection coil can be as small as 1 mA or less, so there is little hysteresis loss and the operating point is always stable, and the coil does not require a large magnetomotive force. It can be easily manufactured because it can be wound using a bobbin instead of directly around the magnetic core.

[Effects of the Invention] As explained above, in the cardiogram transducer according to the present invention, when the body surface is displaced, the relative distance between the magnetic field generating element and the amorphous ferromagnetic ribbon changes via the sensing chip. In this way, changes in the magnetic field applied to the detection coil due to changes in the relative distance are converted into changes in the coil's self-inductance for detection, so it operates with a minute current and has no hysteresis loss. Stable displacement detection of a point can be performed.

Furthermore, the simple structure makes it easy to manufacture, and the magnetic field generating element is fixed inside the shield case and housed integrally within the converter, making it resistant to external noise, offering high sensitivity and excellent operability. It can be easily operated without requiring any special skill, and since the sensing chip is simply brought into contact with the measurement site, there is no pressure on the measurement site.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, FIG. 2 is an enlarged perspective view showing the installed part of the amorphous ferromagnetic thin ribbon, and FIG. 3 is a centering diagram of FIG. Fig. 4 is a circuit diagram showing an example of a circuit for detecting self-inductance, and Fig. 5 is an exploded perspective view showing the structure of the main part of a transducer for cardiac monitoring according to the present invention. FIG. 6 is a diagram showing the relationship between the distance x and the self-inductance L of the detection coil. FIG. Figure 7 is a schematic configuration diagram similar to Figure 1 to explain the problems that occur when a small magnet is fixed on a film stretched over the opening of the shield plate, and Figure 8 is a diagram showing the support member on the lower surface of the shield plate. 9 is a schematic configuration diagram similar to FIG. 1 showing another embodiment in which the lower end surface of the sensing chip is fixed to the upper surface of the film adhered to the film, and FIG. FIG. 3 is a schematic configuration diagram showing still another embodiment in which a portion is provided. 1... Shield case, 2... Amorphous ferromagnetic ribbon, 3... Detection coil, 4... Detection circuit, 5... Body surface, 6... Small magnet (magnetic field generating element), 10, 10' ...Film (intermediate member), 1
5... Shield plate, 15a... Opening, 20,2
0'...Sensing chip.

Claims (1)

[Scope of Claims] 1. A magnetic field generating element that is fixedly disposed within a shielding case and generates a constant magnetic field, and a strip-shaped amorphous ferromagnetic thin strip disposed within the shielding case at a distance from the magnetic field generating element. a detection coil having the amorphous ferromagnetic ribbon as a magnetic core;
A circuit for detecting the self-inductance of the coil by passing a constant minute alternating current through the coil; and a sensing chip made of a non-magnetic material that is brought into contact with the magnetic field generating element through the amorphous ferromagnetic thin strip. A transducer for cardiac imaging, characterized in that it detects displacement of the body surface by converting it into a change and detecting it. 2. The cardiocardiogram converter according to claim 1, wherein the intermediate member is a film stretched over the opening of the shield case.