JPH09269379A - Apparatus for detecting human body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the presence of a human body by supplying an alternating current signal from an LC oscillation circuit to a pair of electrode bodies formed at one face of an insulating substrate and detecting an oscillation frequency of the signal. SOLUTION: A sensor plate 1 has an insulating flexible thin substrate 11. A pair of electrode bodies 12, 13 are arranged side by side via a predetermined distance on one face of the substrate. When a high frequency alternating current signal is impressed from an oscillator 2 consisting of an LC oscillation circuit to the electrode bodies 12, 13, the electrode bodies 12, 13 radiate minute electromagnetic waves. An oscillation frequency at this time is determined by a C component and an L component present in the neighborhood. When a person is on a bed, the oscillation frequency is changed due to the application of a capacitance of the person, which is connected to a frequency detection circuit 3 and measured. A controller 4 recognizes the presence of the person from the change. Accordingly, the presence/absence of the person on the bed can be surely detected in a noncontact manner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a human body detection device, and more particularly, to a human body detection device which can detect the presence / absence of a human body in a non-contact manner, and is particularly suitable for a nursing bed. .

[0002]

2. Description of the Related Art As a method of detecting the presence / absence of a person on a bed, for example, a method using a sensor for detecting infrared rays emitted from a human body, or a weight detection of a piezoelectric element, a load cell, a pressure sensor, or the like is used. Also known are those that utilize changes in the capacitance between metal plates.

[0003]

However, in the infrared detection method, differential output is performed only when the human body moves,
This cannot be detected when the human body is completely stationary. On the other hand, among the weight detection methods, for example, the one that also detects the weight of the bed itself (for example, conductive rubber laid under the bed), the load of the bed is always applied, so the so-called fatigue There is a problem of deterioration over time and damage such as.

Further, in the pressure sensor which is laid on the mat and directly detects the load of the human body, not only the durability problem due to repeated getting on and off, but also the patient feels uncomfortable, and further the mat itself. It has been pointed out that there are problems such as false detections due to the change in shape.

On the other hand, the electrostatic sensor cannot be placed on the mat because it is composed of two hard metal plates having a certain thickness, and it is placed between the mat and the bed frame. However, due to the influence of the metal frame of the bed, it is difficult to obtain sensitivity even on the mat. Also, since electromagnetic waves will be carried on the metal frame,
There was a problem in that the detection level would greatly fluctuate and a malfunction would occur just by touching the metal frame with a hand or the like.

As described above, in terms of detection sensitivity, a contact type sensor placed on a mat and used is preferable,
In terms of durability and usability, a non-contact type that is placed between the mat and the bed frame is preferable, and a sensor that can satisfy both of them, that is, a non-contact type sensor with good detection sensitivity Is desired.

In recent years, beds in which the bed frame can be raised and lowered by a motor or the like are becoming widespread. Even in this type of movable bed, the reliability of reliable operation without being affected by the metal frame. There is a demand for the development of high-performance sensors.

The present invention has been made in order to meet such a demand, and its object is to be thin as a whole and to be arranged, for example, between a mat and a bed frame,
Moreover, it is an object of the present invention to provide a human body detection device capable of reliably detecting the presence / absence of a human body on a mat without being affected by the metal body even if the frame is movable.

[0009]

In order to achieve the above object, the present invention provides a sensor plate having a pair of electrode bodies formed on one surface of an electrically insulating substrate with a predetermined spacing,
An LC oscillation circuit that supplies an AC signal to the pair of electrode bodies, a frequency detection circuit that detects the oscillation frequency of the LC oscillation circuit, and the presence / absence of a human body based on the oscillation frequency detected by the frequency detection circuit. And a human body recognition means for determining.

By applying a high-frequency AC signal from the LC oscillator circuit to the pair of electrode bodies, minute electromagnetic waves are radiated from the electrode bodies. The frequency of the AC signal at this time is determined by the electrostatic capacitance (capacitor) component and / or the inductance component between the sensor plate and the bed frame. And when there is a person on the mat, the capacitor component of the human body is added to it,
The frequency will change.

That is, this human body detecting device not only captures the two electrode bodies of the sensor plate but also the metal frame of the bed itself as a part of the sensor. The state change is detected as a frequency change of the LC oscillator circuit.

In this case, the electrically insulating substrate is a flexible substrate, and at least the LC oscillating circuit is provided on the other surface side of the substrate to unitize the sensor plate so that the space between the mat and the bed frame is increased. It can be easily installed at a predetermined place of the patient without being aware of its existence by the patient.

The LC oscillating circuit does not necessarily have to be a special one, and may be, for example, the well-known Colpitts type oscillating circuit. Further, a known frequency counter may be used as the frequency detection circuit,
Because of this, the overall structure can be inexpensive.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, in order to better understand the technical idea of the present invention, embodiments thereof will be described with reference to the drawings.

As shown in FIG. 1, this human body detecting device includes a sensor plate 1, an oscillator 2 connected to the sensor plate 1, and a frequency detection circuit 3 for detecting the oscillation frequency thereof.
And a human body recognition means 4 for determining the presence / absence of a human body based on the oscillation frequency detected by the frequency detection circuit 3.

Referring also to FIG. 2, the sensor plate 1 is provided with a thin substrate 11 which is electrically insulative and preferably flexible and made of, for example, a soft synthetic resin. In this embodiment, the substrate 11 has a horizontal width W of 750 mm and a vertical width L of 160 m, as shown in the plan view of FIG.
A thin plate having a thickness m and a thickness H of 5 mm is provided, and a pair of electrode bodies (metal plates) 12 and 13 are juxtaposed on one surface of the thin plate at predetermined intervals. According to this embodiment, the width W1 of each electrode body 12, 13 is 200 mm, and the distance D between them is D.
Is 180 mm.

The oscillator 2 is composed of an LC oscillation circuit, and in this embodiment, a voltage division feedback type Colpitts type oscillation circuit is adopted. The oscillator 2 may be a Hartley type oscillation circuit other than the above, and may be a tuning coupling type, that is, any of a collector tuning type, a base tuning type, and an emitter tuning type.

From this LC oscillator circuit 2 to each electrode body 12, 1
A high-frequency AC signal is applied to 3, so that minute electromagnetic waves are radiated from the electrode bodies 12 and 13 into the air. The oscillation frequency at this time is determined by the surrounding capacitor component and inductance component, and a frequency detection circuit 3 is connected to the LC oscillation circuit 2 in order to detect the frequency.

In this embodiment, the frequency detection circuit 3 has a frequency counter 3 including a level conversion circuit 31 in the preceding stage.
2 and the count value is sent to the controller (CPU) 4 as a human body recognition means. In this embodiment, as shown in the side view of FIG.
The oscillation circuit 2 and the frequency detection circuit 3 are provided on the other surface (back surface) side of the substrate 11 to unitize the sensor plate 1. However, only the LC oscillation circuit 2 may be incorporated in the sensor plate 1, and the function of the frequency detection circuit 3 may be provided to the controller 4 side.

FIG. 3 illustrates a state in which the human body detecting device is applied to the movable bed 5. Here, it is assumed that the bed frame 6 of the movable bed 5 is provided with a head side frame 61 and a leg side frame 62 driven up and down by a motor (not shown), and a fixed frame 63 located in the middle. The sensor plate 1 is preferably arranged on the fixed frame 63. It should be noted that each of the frames 61 to 63 is made of metal and is not shown, but actually a mat is placed on the bed frame 6.

Further, FIG. 4 shows an equivalent circuit of the human body and the bed frame 6 for the sensor plate 1 and the LC oscillation circuit 2, and the operation of the present invention will be described based on this. First, when there is no person on the bed, the oscillation frequency of the LC oscillation circuit 2 is the same as the electrode bodies 12, 13 of the sensor plate 1.
Capacitance (capacitor component) C1 between them, and capacitance C between the sensor plate 1 including the LC oscillation circuit 2 and the bed frame 6
2, C3 and the inductance L0 of the bed frame 6 are determined.

Therefore, the frequency f0 at this time is

[Equation 1] It is represented by Note that L and C are constants in the LC oscillator circuit 2.

On the other hand, when a person is present on the bed, the equivalent capacitance C0 possessed by the person is added to the oscillation frequency f1 from the state where the person is not present.

[Equation 2] Therefore, the oscillation frequency is f0 as much as the equivalent capacitance C0 is added.
→ Change to f1.

When the oscillating frequency of the LC oscillating circuit 2 was actually measured, the oscillating frequency of the sensor plate 1 alone was about 21 MHz. The oscillation frequency f0 when there is no person on the bed is about 17 MHz, and after the installation on the bed frame 6, the frequency f0 (about 17 MH).
The stable oscillation was repeated in z).

In this oscillation state, when a person rides on the bed and lies down, the oscillation frequency is about 500 kHz.
To some extent. That is, in this embodiment, the oscillation frequency changes by about 500 kHz when the person is on the bed and when the person is not on the bed, and the controller 4 recognizes the presence / absence of the person based on the change. This frequency change state is illustrated in FIG. 5, and according to this, it can be recognized as “absent” at the oscillation frequency f0 and “present” at the oscillation frequency “f1”.

By the way, in the case of the movable bed 5, the oscillation frequency of the LC oscillation circuit 2 is changed by undulating the bed frame 6. FIG. 6 shows a state in which the oscillation frequency changes when a person is lying on the bed and the head side frame 61 is raised up to the position (about 30 degrees with respect to the horizontal) shown by the chain line in FIG. It is shown. According to this, when the head-side frame 61 is raised to the above-mentioned angle even when there is a person on the bed, the oscillation frequency is f1 → f2 (however, f2 <f0, as when the person leaves the bed). ).

Further, in FIG. 7, with the person lying on the bed, the head side frame 61 is raised to the position shown by the chain line in FIG. A graph of the change state of the oscillation frequency when 61 is returned to the original position indicated by the solid line is shown. According to this, LC
It can be seen that the oscillation frequency of the oscillation circuit 2 returns as f1 → f2 → f1.

In any case, even though there is a person on the bed, the oscillation frequency changes from f1 to f0, resulting in the same state as when the person got out of bed. Since the undulating speed of the bed frame is slower than the speed at which a person gets on and off the bed, the threshold value of the changing speed (rise or fall time) of the oscillation frequency is set in the controller 4 in advance. The controller 4 can discriminate whether it is due to a person getting on and off the bed frame or due to ups and downs of the bed frame.

As described above, according to the present invention, the presence / absence of a person on the bed can be detected by the oscillation frequency of the LC oscillation circuit 2. For example, as shown in FIG. The recumbent area is divided into a plurality of areas (for example, 6 areas), the sensor plate 1 is arranged in each area, and the fluctuation of the oscillation output is tracked over time, so that the movement of the patient on the bed is also monitored. can do.

Furthermore, by converting the change in frequency obtained from the sensor plate 1 into, for example, a voltage and applying it to a low-pass filter, it is possible to detect even the respiration and heart rate of the patient on the bed. Further, in this human body detection device, since the electromagnetic waves handled by the human body detection device are extremely small, the influence on the human body and pacemaker can be neglected and the device can be used safely.

Although the sensor plate 1 is installed on the fixed frame 63 in the above embodiment, it may be installed on the head side frame 61 or the leg side frame 62 depending on the case. In addition to being applicable to a movable bed, it can be applied not only to a normal bed, but further, it can be used as a non-contact type sensor such as an automatic door in an operating room of a hospital, for example. There are uses.

[0032]

As described above, according to the present invention,
Despite its simple structure, it can reliably detect the presence / absence of a person on the bed in a non-contact manner without being affected by the metal frame of the bed, and a sensor particularly suitable for a movable bed is provided. .

Further, since the sensor plate is a thin plate and can be easily unitized by incorporating a peripheral circuit such as an LC oscillating circuit, it is easy to handle and it can be inserted between the mat and the bed frame. By installing it, it can be applied to existing beds as it is.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic circuit configuration of a human body detection device according to the present invention.

2A and 2B are a plan view and a side view of a sensor plate which is a constituent element of the human body detection device.

FIG. 3 is a schematic diagram showing a state in which the sensor plate is applied to a movable bed.

FIG. 4 is an electrical equivalent circuit of the sensor plate and a human body and a bed frame.

FIG. 5 is a graph for explaining the operation of the present invention.

FIG. 6 is a graph for explaining the operation of the present invention.

FIG. 7 is a graph for explaining the operation of the present invention.

FIG. 8 is an explanatory view showing an arrangement example of the sensor plate on a bed frame.

[Explanation of symbols]

 1 Sensor Plate 11 Substrate 12, 13 Electrode Body 2 LC Oscillation Circuit 3 Frequency Detection Circuit 31 Level Conversion Circuit 32 Frequency Counter 4 Controller (CPU) 5 Movable Bed 6 Bed Frame

Claims (4)

[Claims] 1. A sensor plate having a pair of electrode bodies formed on one surface of an electrically insulating substrate with a predetermined interval,
An LC oscillation circuit that supplies an AC signal to the pair of electrode bodies, a frequency detection circuit that detects the oscillation frequency of the LC oscillation circuit, and the presence / absence of a human body based on the oscillation frequency detected by the frequency detection circuit. A human body detection device comprising: a human body recognition means for determining 2. The human body detection device according to claim 1, wherein the electrically insulating substrate is a flexible substrate, and at least the LC oscillation circuit is provided on the other surface side of the substrate. . 3. The human body detection device according to claim 1, wherein the LC oscillator circuit is a Colpitts oscillator circuit. 4. The human body detection device according to claim 1, wherein the frequency detection circuit is a frequency counter.