JPH0357206Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention is a cardiac sensor that detects as an electrical signal the change in inductance of the coil element of the sensor body in response to the displacement of a magnet fixed to the human skin. The present invention relates to an engagement structure between a holder attached via a membrane and a sensor body.

(Prior Art) Conventionally, cardiac sensors that detect chest wall vibrations or blood vessel site vibrations that occur with myocardial activity have been used that have semiconductor pressure sensing elements or piezoelectric elements. This conventional method involves manually pressing a sensor onto the carotid artery and femoral artery, and analyzing the signal waveform (cardiac diagram) in response to pressure changes caused by myocardial activity, or comparing the cardiac diagram with an electrocardiogram. Based on this, he diagnosed arteriosclerosis, various valvular diseases, etc. However, since the output signal of cardiac sensors using semiconductor pressure sensing elements or piezoelectric elements changes when the sensor is pressed against the skin, testing requires skill.

Cardiac sensors shown in FIGS. 5 to 9 have been developed to solve this drawback.
As shown in FIG. 5, this cardiac sensor has a magnet 3 attached to a part of the skin 1 corresponding to an artery 2 such as the carotid artery.
It is attached by adhering the adhesive thin film 4 covering this to the skin 1. A separate sensor body 6 is attached to the thin film 4 and magnet 3.
The magnet 3 is set in the bottom recess 8 of the outer case 7.
A shield case 9 made of non-magnetic metal is fitted, and an even number of coil elements 12 each having a winding 11 around a magnetic wire 10 are inserted in the shield case 9 radially and circumferentially as shown in FIG. The resin 13 is arranged at equal intervals (that is, so that the elements 12 facing each other across the center are in point-symmetrical positions).
It accommodates an element stand 14 molded with a mold and a substrate 16 provided with a signal processing circuit 15 for processing output signals of the group of elements 12, and a lead wire 17 is connected to the signal processing circuit 15 to be drawn to the outside. .

As shown in FIG. 6, the connection of the winding 11 of the element 12 is divided into the solid line a and the dotted line b for each element 12, and the solid line a is connected to one of the DC power sources. The poles, for example, the positive electrode common terminal 18 side are connected to the outer end of each winding 11, and the negative electrode terminal 19 side is connected to the inner end of each winding 11, so that they are connected in series, and the connection indicated by dotted line b is
On the contrary, they are connected in series so that the positive electrode common terminal 18 side is connected to the inner end of the winding 11 and the negative electrode terminal 19 side is connected to the outer end of the winding 11.

The sum of the inductances of the two sets of elements 12 connected by these lines a and b differs depending on the position of the magnet 3. That is, as shown in FIG. 7, the magnetic flux Bφ generated in the element 12 by the current flowing through the line b and the magnetic flux Mφ caused by the magnet
However, with respect to the magnetic flux Aφ generated in the element 12 due to the current flowing through the wire a, the magnetic flux Mφ caused by the magnet 3 is biased in the forward direction, and the magnetic wire 10 is saturated, resulting in a difference in inductance. Note that, for example, the winding 11 connected to the wire b
If the winding direction of the magnetic wire 10 is reversed,
A current is passed through line b in the opposite direction to that shown.

As a circuit for detecting the difference in inductance depending on the position of the magnet 3, for example, a circuit as shown in FIG. 8 is used. That is, a winding group 11a connected to the wire a and a winding group 1 connected to the wire b.
One end of 1b is commonly connected to the power terminal 18 side,
The other ends are connected to the collectors of transistors 21 and 22, respectively, and the emitters of transistors 21 and 22 are connected to the other ends (ground) of the electrodes via resistors 25 and 26, respectively, and the bases of one of transistors 21 and 22 are connected to the other transistor 22,
By connecting the collector of transistor 21 to the collector of transistor 2 through parallel circuits 24 and 23 consisting of a capacitor and a resistor, an astable multivibrator is constructed.
The difference between the emitter voltages of magnets 1 and 22 is converted into a DC voltage by a high-cut filter (integrator circuit) 27, and the DC voltage is amplified by an amplifier circuit 28 to obtain an output voltage from an output terminal 29. The relationship between the position and the output voltage from the output terminal 29 is as shown in FIG. In other words, the closer the magnet is to the element 12, the higher the operating frequency of the multivibrator (for example, configured to vary in the range of 60kHz to 500kHz) and the higher the emitter voltage. L1 is uniquely determined
The linear region of ~L2 is designed to fall within the operating range of the magnet 3. Also, magnet 3 and element 1
The position No. 2 (operating point) is set at approximately the midpoint of the linear region of sensitivity, as shown in FIG. Furthermore, the responsiveness of the sensor can be changed by changing the time constant of the high-cut filter 27, and the time constant is determined by the frequency of change in the signal to be measured.

A sensor consisting of such radially arranged elements 12 cancels out the disturbance magnetic field, and the magnet 3
This has the advantage that the effects of uneven magnetization can also be canceled out.

Note that since there is also a correlation between the distance of the magnet 3 and the operating frequency of the multivibrator, it is possible to obtain a signal corresponding to the operating frequency as a signal indicating the distance, but the signal processing circuit 15 is complicated.

(Problem that the invention aims to solve) The cardiac sensor that detects changes in inductance due to the movement of the magnet 3 as changes in electrical signals requires less skill than conventional sensors that detect pressure, etc. Although it has the advantage of not requiring
There was also a problem in that the sensor body 6 had to be held manually for about two minutes at most during the measurement.

In order to solve these problems, the present inventors fixed a stretchable film 43 to a ring-shaped holder 38 and fixed a magnet 3 to the upper surface of the film 43, as shown in FIG. , a rising piece 40 is provided around the holder 43, a recess 40x is provided at the same height on the inner surface of each rising piece 40, and the sensor body 6 is provided with a recess 40x.
However, the sensor main body 6 is detachably attached to the holder 38 by elastically fitting the projection 6a provided around the recess 40x into the recess 40x.
However, if the pressing force of the sensor body 6 against the holder 38 is too large, the protrusion 6a will pass through the recess 40x and the sensor body 6 will be tilted as shown by the two-dot chain line a, and the pressing force will be biased. If the sensor main body 6 is not mounted horizontally on the holder 38, the distance of the element 12 to the magnet 3 may change, which may cause problems in that proper measurement may not be possible. In particular, when measuring the femoral artery, the holder 38
It is difficult to visually see the mounting location of the sensor body 6, and the sensor body 6 is often not properly mounted on the holder 38.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a cardiac sensor that detects as an electrical signal the change in inductance of the coil element of the sensor body in response to the displacement of a magnet fixed to the human skin. , a projection is provided on the top surface of the bottom plate of the ring-shaped holder to which the magnet is attached via a stretchable film, and supports the center body by contacting the bottom surface of the center body, and a plurality of rising pieces are provided around the holder. , a locking protrusion protruding inward is provided on the rising piece, a protrusion is provided around the case of the sensor body to be engaged with the locking protrusion, and the protrusion of the case and the It is characterized in that at least one of the locking surfaces of the locking protrusion is formed into an inclined surface that presses the center body toward the holder.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. In Figures 1 to 3, 3
0 is a sensor body, and 38 is a resin holder to which the magnet 3 is attached with the following structure. Holder 38
A plurality of (preferably 4 or more, 8 in the illustrated example) are arranged around the ring-shaped bottom plate portion 39.
A rising piece 40 is provided, and a locking protrusion 40a protruding inward is formed on the top of each rising piece 40 to lock a protrusion 32a formed around the resin case 32 of the sensor main body 30. ing. As shown in FIG. 2, the upper and lower surfaces b, c of the projection 40a and the upper and lower surfaces d, e of the locking projection 40a are formed into inclined surfaces (tapered shapes).

Further, on the upper surface of the bottom plate portion 39 of the holder 38, three or more (eight in the illustrated example) protrusions 41 are formed to abut and support the bottom surface of the case 32. The projection 41 does not have a rod shape as in the embodiment, but may be a cylindrical projection formed concentrically on the holder 38. Further, on the lower surface of the bottom plate portion 39,
A stretchable film 43 made of nonwoven fabric, a resin film, or the like is fixed with an adhesive 42, and a magnet 3 is fixed with an adhesive 44 at the center of the upper surface of the stretchable film 43.
These films 43 and magnets 3 may be fixed by heat welding. Further, an adhesive 45 is applied to the lower surface of the membrane 3, that is, the surface facing the skin of the human body, and the coated surface is covered with a release paper 46. It has a tongue piece 46a to facilitate peeling.

As shown in FIG. 3, the sensor main body 30 of this embodiment has an even number of elements 12 each having a winding 11 wound around a magnetic gland 10 on one side of the substrate 16, that is, the surface facing the magnet 3. , as described above, are arranged radially and at equal intervals in the circumferential direction so that the elements facing each other across the center are point symmetrical and molded with resin 47, thereby preventing relative movement of the element 12 with respect to the substrate 16. In addition, the signal processing circuit 15 of the element 12 is provided on the opposite side of the board 16, and the signal processing circuit 15 is covered with a shield case 31 made of a non-magnetic material such as brass or aluminum. The lead wire 17 connected to the signal processing circuit 15 is pulled out from the case 32, and the element 12, the substrate 16, and the shield case 31 are integrated with resin, thereby forming the sensor body 30 and achieving a thinner design. ing. Further, a lead wire accommodating portion 48 through which the lead wire 17 is passed is formed on the upper surface of the case 32 to protrude upward and extend in the radial direction.
As shown in FIG.
0 to facilitate gripping, and the sensor body 30
This contributes to the miniaturization of the product and reduces costs.

The sensor of this embodiment is manufactured by holding the tongue piece 46a of the release paper 46 shown in FIG. 1 and peeling off the membrane.
3 is exposed, and the holder 38 is adhered to the skin together with the membrane 43 so that the magnet 3 is positioned above the artery (carotid artery, femoral artery, etc.) 2, and the sensor body 30 is attached to the holder 38. Fit and measure. At this time, the bottom surface of the case 32 is
1, the protrusion 32a around the case 32 is elastically engaged with the engagement protrusion 40a of the rising piece 40, so that the magnet 3 is brought into contact with the element 1.
2, and as the skin 1 in that area protrudes and retracts as the artery 2 moves, the magnet 3 follows and operates, and the signal processing circuit 15 causes the magnet 3 to move according to the principle described above. An output corresponding to the position is outputted to a measuring device (not shown) via the lead wire 17.

Further, as shown in FIG. 2, the upper and lower surfaces b, c of the protrusion 32a on the outer periphery of the case 32 and the upper and lower surfaces d, e of the locking protrusion 40a of the rising piece 40 are formed as inclined surfaces, so that the sensor The main body 30 can be easily attached to and detached from the holder 38. In addition, when the two are engaged, the elasticity of the rising piece 40 causes the protrusion 32a to be pressed by the locking protrusion 40a in the direction of inclination indicated by F1.
The bottom surface of is pressed against the protrusion 41 and is supported under the reaction force of F2.

As shown in FIG.
8, the locking surfaces of the protrusion 32a and the locking protrusion 40a do not need to be both sloped surfaces, and as shown in FIG.
As shown in FIG.
Alternatively, as shown in B, only the upper and lower surfaces b and c of the protrusion 32a of the case 32 may be formed as inclined surfaces.

(Effects of the invention) As described above, in the present invention, the center body is supported by bringing the magnet into contact with the bottom surface of the center body on the top surface of the bottom plate of the ring-shaped holder attached via the elastic film. a plurality of rising pieces are provided around the holder, a locking protrusion protruding inward is provided on the rising piece, and a locking protrusion is provided around the case of the sensor body to engage with the locking protrusion. A locking protrusion is provided, and the locking surface of at least one of the case protrusion and the locking protrusion is formed into an inclined surface that presses the center body toward the holder. The center body is held in the holder with the sensor body always pressed against the protrusion, so the center body is not pushed too far into the holder, and there is insufficient pushing force to ensure that the sensor body is properly attached. The position of the sensor body relative to the holder, that is, the reference position of the sensor body relative to the magnet, is kept constant even when the cardiac sensor is installed in a location that is difficult to see, such as when measuring the femoral artery. and measurements can always be made accurately.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an embodiment of the present invention with the holder and sensor main body separated, Fig. 2 is a sectional view showing the structure of the holder, sensor main body, and engaging portion of the embodiment, and Fig. 3 4A and 4B are sectional views showing other examples of the engagement structure according to the present invention; FIG. The figure is a sectional view showing a conventional cardiac sensor, FIG. 6 is a plan view showing the arrangement of elements of a conventional cardiac sensor, FIG. 7 is an explanatory diagram of the operation of the element, and FIG. 8 is a signal processing circuit of the element. A circuit diagram showing an example, FIG. 9 is a relationship diagram between the distance of the magnet and the output voltage of the signal processing circuit,
FIG. 10 is a side sectional view illustrating the problems of the conventional structure.

Claims (1)

[Scope of utility model registration request] In a cardiac sensor that detects as an electrical signal the change in inductance of the coil element of the sensor body in response to the displacement of a magnet fixed to the human skin, the center body a protrusion that supports the center body by abutting on the bottom surface of the center body;
A plurality of rising pieces are provided around the holder, and a locking protrusion that protrudes inward is provided on the rising piece, and a protrusion that is locked to the locking protrusion is provided around the case of the sensor body. An engagement structure for a cardiac sensor body and a holder, characterized in that a locking surface of at least one of the protrusion of the case and the locking protrusion is formed into an inclined surface that presses the center body toward the holder. .