The present invention relates to a measurement device for measuring a core temperature of a measurement target such as a living body.
Conventionally, a technique for non-invasively measuring a core temperature of a living body is known. For example, Patent Literature 1 discloses a technique for estimating a core temperature of a living body assuming a pseudo one-dimensional model in a living body B, a measuring instrument 40 including a temperature sensor and a heat flux sensor, and outdoor air.
In the technique disclosed in Patent Literature 1, a core temperature of a living body is estimated assuming a one-dimensional model of biological heat transfer illustrated in
In Patent Literature 1, a core temperature of a living body is estimated from the following relational expression (i).
Core temperature (Tbody)=Temperature (Tskin) of contact point between temperature sensor and skin+Coefficient of proportionality (Rsensor)×Heat flux (Hsignal) flowing into temperature sensor (1)
The coefficient of proportionality (Rsensor) can be generally obtained by giving a rectal temperature or an eardrum temperature measured using a sensor such as another temperature sensor as a core temperature (Tbody), and thus the core temperature of the living body can be estimated by measuring a heat flux (Hsignal) flowing into the temperature sensor.
However, in a case where a one-dimensional model is assumed as a heat transfer model of a living body as in Patent Literature 1, when heat flows into the sensor from outdoor air due to generation of wind or the like, as illustrated in
Therefore, when wind or the like is generated, the Leak Ratio increases, and the above-described one-dimensional model is no longer established for the Hsignal, and in the core temperature measurement technique of the related art, there is a problem that an erroneous core temperature is measured when wind or the like is generated around the sensor.
Embodiments of the present invention have been made to solve the above-described problems, and an object of embodiments of the present invention is to provide a measurement device capable of accurately measuring a core temperature by suppressing a change in thermal resistance between a sensor and outdoor air even when wind or the like is generated around the sensor.
In order to solve the above-described problems, there is provided a measurement device according to embodiments of the present invention including: a measuring instrument configured to measure a heat flux transported from a measurement target; a first member having a hollow structure and including the measuring instrument therein; a second member having a hollow structure and covering the first member to form an air layer between the first member and the second member; and a third member that is disposed between the first member and the second member and transports the heat flux from the measurement target outside the first member to an upper portion of the second member.
According to embodiments of the present invention, since the first member having the measuring instrument, and the second member forming the air layer between the first member and the second member, are provided, and the third member that transports the heat flux from the measurement target outside the first member to the upper portion of the second member is further provided between the first member and the second member, it is possible to provide a measurement device capable of suppressing the change in the thermal resistance between the sensor and the outdoor air and accurately measuring the core temperature even when wind is generated around the sensor.
Hereinafter, a preferred embodiment of the present invention will be described. In the following embodiment, the measurement target is a living body, and the measurement surface on which the measurement device is disposed is a surface of the skin of a living body that is the measurement target.
<Summary of Embodiments of Present Invention>
The measurement device of embodiments of the present invention includes a first member having a hollow structure and including a measuring instrument for measuring a heat flux therein, and a second member having a hollow structure and forming an air layer between the second member and the first member, and further includes a third member that transports a heat flux from a measurement target outside the first member to an upper portion of the second member between the first member and the second member.
In the measurement device of embodiments of the present invention, the third member that transports the heat flux from the measurement target to the upper portion of the second member is provided in addition to the first member having the measuring instrument that measures the heat flux and the second member forming the air layer between the first member and the second member, and accordingly, it is possible to increase the temperature of the upper portion of the measuring instrument. Therefore, even when wind is generated around the measurement device, it is possible to suppress the change in the thermal resistance between the measuring instrument and the outdoor air, suppress the leak heat flux that causes the measurement error of the core temperature, and reduce Leak Ratio. Hereinafter, a specific configuration of the measurement device of the present embodiment will be described.
<Configuration of Measurement Device>
The measurement device 1 of
In the configuration example of
The measuring instrument 40 disposed inside the first member 10 includes a temperature sensor 40a (first temperature sensor) configured to measure the temperature of skin SK as a measurement surface, and a temperature sensor 40b (second temperature sensor) disposed at a position immediately above the temperature sensor 40a to face the temperature sensor 40a. In the configuration example of
The first member 10 has a hollow structure, and the inside thereof is filled with air. The second member 20 is desirably filled with a material having high thermal resistance, and a cavity such as air can be used.
As the first member 10 and the second member 20, a material (approximately 0.1 mm) capable of reducing the thermal resistance and the thickness is desirable, and polyethylene terephthalate (PET) or the like can be used. As a material constituting the truncated third member 30 having a hollow shell structure, a material having high thermal conductivity is desirable in order to efficiently transport heat flux. For example, the third member 30 can be configured using a thin film such as aluminum or the like.
The first member 10 is disposed on the skin SK of the living body B as a measurement surface. The first member 10 has a hollow structure formed of a thin film, and can have, for example, a cylindrical outer shape. The second member 20 is disposed on the skin SK of the living body B as a measurement surface to cover the first member 10, and forms an air layer between the first member 10 and the second member 20. Similarly to the first member 10, the second member 20 has a hollow structure formed of a thin film, and can have a cylindrical outer shape. Furthermore, the outer shapes of the first member 10 and the second member 20 are not limited to the cylindrical shape, and may be, for example, a rectangular parallelepiped shape having a hollow structure.
The diameters D of the cylindrical shape of the first member 10 and the cylindrical shape of the second member 20 can be, for example, 20 mm and 30 mm, respectively. A height t of the second member 20 based on the skin SK that is a measurement surface can be, for example, approximately 6 mm. A height t of the first member 10 based on the skin SK that is a measurement surface can be, for example, approximately 3 mm.
In this manner, the air layer formed by the first member 10 and the air layer between the first member 10 and the second member 20 on the outer side thereof are formed, and the air inside each of the first member 10 and the second member 20 is configured not to move.
Furthermore, the third member 30 is disposed between the first member and the second member, the upper surface portion thereof is brought into contact with the upper surface portion of the second member 20, and accordingly, the heat flux from the living body B is transported to the upper portion of the second member outside the first member. In the example of
<Configuration of Sensor in Measuring Instrument>
The temperature sensor 40a is disposed on an inner surface of a bottom surface portion where the cylindrical first member 10 is in contact with the skin SK that is a measurement surface. On the inner surface of the upper surface portion of the first member 10, the temperature sensor 40b is disposed at a position immediately above the temperature sensor 40a to face the temperature sensor 40a. In the configuration example of
In
In the configuration example of
In
In
<Configuration Example of Third Member>
The third member 30 is a member that is disposed in the space between the first member 10 and the second member 20, transports the heat flux from the measurement target to the upper surface portion of the second member outside the first member to increase the temperature of the upper surface portion of the second member, that is, the temperature of the upper portion of the measuring instrument 4o, and thereby functions to suppress the leakage heat flux HLeak and reduce the Leak Ratio. As the configuration of the third member 30, configurations of various shapes can be adopted as long as the shape can exhibit this function.
For example, in the case of being disposed between the first member and the second member having a cylindrical shape, the third member can be configured to have a conical shape. By forming the third member in a conical shape, it is possible to transport the heat flux from the measurement target to the upper surface portion of the second member outside the first member without affecting the heat flux flowing into the measuring instrument 40. It can also be configured to have a truncated shape as shown in
Further, the configuration of the third member 30 is not limited to the conical shape or the truncated shape, and other cone shapes can be adopted. For example, when the second member 20 has a rectangular parallelepiped shape, the third member 30 can accordingly have a pyramid shape or a truncated pyramid shape. By forming the third member in a frustum shape, a larger amount of heat flux can be transported to the second member without affecting the heat flux flowing into the measuring instrument 40, and the effect of temperature rise can be enhanced.
As illustrated in
<Temperature Field and Heat Flux in Present Embodiment>
In
<Heat Equivalent Circuit of Present Embodiment>
The heat equivalent circuit of
Here, when the truncated third member 30 is sufficiently large, the end portion of the bottom surface of the truncated third member 30 is disposed at a position sufficiently away from the measuring instrument 40, and thus, the heat flux from the living body B is collected by the third member 30 on the first outer side and transported to the upper surface portion of the second member 20.
The heat flux Hplus collected and transported by the truncated third member 3o increases the temperature of the upper surface portion of the second member 20 without affecting the Hsignal, and as a result, the temperature outside the measuring instrument 40 can be increased. In the heat equivalent circuit of
The truncated third member 30 is covered with the second member 20, and the distance to the outdoor air decreases toward the vicinity of the central portion where the measuring instrument 40 is disposed, and becomes substantially 0 in the vicinity of the central portion where the measuring instrument 40 is disposed. Accordingly, the effect of suppressing the inflow of heat from the outdoor air to the sensor increases toward the vicinity of the central portion, and the effect of reducing the highest Leak Ratio can be obtained in the vicinity of the central portion where the measuring instrument 40 is disposed. As a result, it is possible to reduce the difference between the heat flux H′signal measured by the temperature sensor or the heat flux sensor and the Hsignal to be originally measured, and to reduce the measurement error.
<Comparison Result of Measurement Error>
<Effects of Present Embodiment>
According to the present embodiment, the first member 10 including the measuring instrument that measures the heat flux and the second member 20 forming the air layer between the first member 10 and the second member 20 are provided, and the third member that transports the heat flux from the measurement target outside the first member to the upper surface portion of the second member is further provided between the first member and the second member. Therefore, even when the temperature outside the measuring instrument increases due to the heat flux transported to the upper surface portion of the second member and wind is generated around the measurement device, it is possible to suppress the change in the thermal resistance between the sensor and the outdoor air, suppress the leakage heat flux that causes the measurement error, and reduce the Leak Ratio to reduce the measurement error when measuring the core temperature.
<Configuration Example of Measurement Device>
A configuration of the measurement device 1 according to the present embodiment will be described with reference to
The measurement device 1 includes, for example, the measuring instrument 40, the arithmetic circuit 50, the memory 60, the communication circuit 70 that functions as an I/F circuit with the outside, and the battery 80 that supplies power to the arithmetic circuit 50, the communication circuit 70, and the like on a sheet-like base material 90.
In the configuration example of
In the configuration example of
The memory 60 stores the information on the one-dimensional biological heat transfer model based on the above-described Equation (i) and the estimation result of the core temperature. The memory 60 can be realized by a predetermined storage area in a rewritable nonvolatile storage device (for example, a flash memory or the like) provided in the measurement system.
The communication circuit 70 outputs the time-series data of the core temperature Tc of the living body B generated by the arithmetic circuit 50 to the outside. As the communication circuit 70, when data or the like is output by wire, an output circuit to which a USB or other cables can be connected is used, but for example, a wireless communication circuit conforming to Bluetooth (registered trademark), Bluetooth Low Energy, or the like may be used.
The sheet-like base material 90 functions as a base for placing the measurement device 1 including the measuring instrument 40, the arithmetic circuit 50, the memory 60, the communication circuit 70, and the battery 80, and further includes wiring (not illustrated) for electrically connecting these elements. Assuming that the measurement device 1 is connected on the skin of a living body, it is desirable to use a deformable flexible board for the sheet-like base material 90.
In addition, an opening is provided at a part of the sheet-like base material 90, and the temperature sensor 40a and the heat flux sensor 40c included in the measuring instrument 40 are placed on the base material 90 to be in contact with the measurement surface of the skin SK of the living body B from the opening.
Here, the measurement device 1 is realized by a computer. Specifically, the arithmetic circuit 50 is realized by, for example, a processor such as a CPU or a DSP executing various data processing according to a program stored in a storage device, such as a ROM, a RAM, and a flash memory, including a memory 60 provided in the measurement device 1. The program for causing the computer to function as the measurement device 1 can be recorded on a recording medium or provided through a network.
In
<Modification of Embodiment>
Although the embodiments of the measurement device of the present invention have been described above, the present invention is not limited to the described embodiments, and various modifications that can be assumed by those skilled in the art can be made within the scope of the invention described in the claims.
This application is a national phase entry of PCT Application No. PCT/JP2020/027245, filed on Jul. 13, 2020, which application is hereby incorporated herein by reference.
Filing Document | Filing Date | Country | Kind |
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PCT/JP2020/027245 | 7/13/2020 | WO |