JPS6111638Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a heat flow sensor, and particularly to a wafer type heat flow sensor.

A heat flow sensor measures the heat flow density that radiates heat from the surface of an object to the atmosphere, or measures the heat flow density that diffuses within the object. In the former measurement, the heat flow sensor is used in close contact with the surface of the object to be measured, and in the latter measurement, it is used embedded in the object to be measured. Furthermore, the wafer-type heat flow sensor measures the heat flow density from the temperature difference between the front and back surfaces of a wafer-shaped (thin plate-shaped) thermal resistor in the above-described heat flow sensor. That is, as shown in FIG. 1, the wafer-type heat flow sensor is equipped with a wafer-shaped thermal resistor 1, a temperature measuring element 2, etc., and the temperature difference between both surfaces ΔT=T ₁ − due to the heat flow density indicated by the arrow. T ₂ is measured by the temperature measuring element 2, and the heat flow density is detected based on this measured amount.

Incidentally, in such a wafer-type heat flow sensor, it is preferable to make the thickness small relative to the effective area of the sensor so that it can be ignored. This is because, as the thickness of the sensor increases, errors occur due to the deviation angle between the direction of the heat flow leaking from the side wall of the sensor and the direction of the heat flow being measured, and the direction of the sensor's normal vector n (Fig. 1). This is because it will be put away. In other words, the physical quantity to be detected is a one-dimensional component of heat flow density in a predetermined direction, for example, the component in the normal direction to the surface of the object to be measured, whereas the sensor itself has a finite thickness, so the measurement is difficult. It becomes two-dimensional. Therefore, it is preferable to make the finite thickness negligible as much as possible.

In addition, if the thickness of the heat flow sensor is large, the disturbance to the heat flow to be measured will be large, and if the sensor is used in close contact with the surface of the object to be measured, the state of gas convection will change significantly depending on the presence or absence of the sensor.
The value (heat flow density) under conditions different from the heat flow density in the situation you want to know will be obtained. Therefore,
In order to measure the ideal heat flow density, the sensor needs to be thin.

By the way, there are two points that have been the bottleneck in reducing the thickness of conventional sensors. The first problem is the thermal conductance of the thermal resistor. In other words, thermal conductance is the average thermal conductivity of a thermal resistor divided by its thickness, so the thinner the thermal resistor is, the larger the thermal conductance becomes. The temperature difference between both sides of the resistor becomes small. That is, the sensitivity of the heat flow sensor decreases, and in some cases, a stable amplifier with a high amplification factor is required to obtain a sufficient detection output. This is not desirable because of the high level of technology and high cost of the electric circuit section.

The second problem is mechanical strength. That is,
Hard thermally resistant materials generally have high thermal conductivity, and therefore detection sensitivity cannot be sufficiently increased with a thickness that seems reasonable based on the above description. On the other hand, materials with low thermal conductivity, such as asbestos, foamed polyurethane, and foamed polystyrene, are soft and brittle, so if they are used as thermal resistors and their thickness is reduced, they can be used as heat flow sensors. It was not possible to obtain sufficient strength for practical use.

This idea was devised against the above background, and its purpose is to provide a thin wafer-type heat flow sensor that has no problems in terms of sensitivity and mechanical strength. .

In order to achieve this purpose, this invention makes a wafer-shaped thermal resistor material hard, and forms one or more through holes in the thermal resistor along the thickness direction of the thermal resistor. I have to.

Examples of this invention will be described below. FIG. 2 shows a first embodiment of this invention. In FIG. 2, the heat flow sensor of the first embodiment includes a wafer-shaped thermal resistor (hereinafter referred to as wafer) 11, a thermopile 12, a thermocouple 13, a covering material 14, and an electric circuit section 15.

The wafer 11 is made of a hard heat-resistant material such as silicone, glass fiber composite, epoxy resin, polyimide, polyamide, Bakelite, etc., and its thickness is thinner, for example, 0.5 mm, compared to conventional similar materials. It is configured. and,
The increase in thermal conductance due to such thinning is compensated for by lowering the apparent thermal conductivity of the wafer 11. That is, the wafer 11 has through holes 1 along its thickness direction.
6 (see Figure 3) are formed (second
(omitted in the figure). And, for example, the thermal conductivity of silicone, glass fiber composite is about 0.2
The thermal conductivity of air is approximately 0.022 kcal/mh°C, which is one order of magnitude lower. Therefore, the thermal conductivity of the wafer 11 is suppressed to be smaller than that of a single wafer by the area occupied by the air layer of the through hole 16, and the apparent thermal conductivity is reduced. I would like to add that the silicone and glass fiber composite materials used here are useful for maintaining mechanical strength and structure as a heat resistor, and the increase in heat resistance is intended to be achieved by the size of the air holes. I have it too. Note that the through holes 16 may be formed in a regular arrangement as shown in FIG. 3 or 4, respectively, or may be formed in a random arrangement as shown in FIG. .

The thermopile 12 is for extracting the temperature difference between both sides of the wafer 11 as thermoelectromotive force.
That is, the hot junction 18 of the thermopile 12 is arranged on one side of the wafer 11, and the cold junction 17 is arranged on the other side. Further, the thermocouple 13 is used to correct the value (sensitivity) since the sensitivity of the heat flow sensor changes depending on the temperature, and its hot junction 19 is attached to one surface of the wafer 11. A covering material 14 is fixed to both surfaces of the wafer 11 so as to cover the thermopile 12 and thermocouple 13.

The electric circuit section 15 generates an output according to the heat flow density based on the outputs of the thermopile 12 and the thermocouple 13, and further displays the heat flow density value.

With the above configuration, when the heat flow sensor is set in a heat flow, a temperature difference occurs between both surfaces of the wafer 11, and a detection output is generated from the thermopile 12 in response to this. Then, this detection output and thermocouple 1
Based on the correction output of No. 3, an output corresponding to the heat flow density is generated from the electric circuit section 15.

In this embodiment, although the thickness of the wafer 11 is reduced, the apparent thermal conductivity is reduced due to the presence of the through holes. Sensitivity can be maintained. Moreover, since the wafer 11 is made of a strong and hard heat resistor material, the mechanical strength can be sufficiently increased.

In the above embodiments, the thermopile 12 was used to detect the temperature difference between both sides of the wafer 11, but as shown in FIG. Good too. Note that in FIG. 6, parts corresponding to those in FIG. 2 are given corresponding numbers, and their explanations are omitted.

Next, a second embodiment of this invention will be described. 7 and 8 show a second embodiment. 7 and 8, the heat flow sensor of the second embodiment consists of a substrate (thermal resistor) 21, a thermistor 22, and a covering material 23. In FIG. A through hole 24 having a sufficiently larger area than the thermistor 22 is formed in the center of the substrate 21 . The covering material 23 covers both sides of the substrate 21, and thereby closes the through hole 24 of the substrate 21 and blocks the internal air layer from the outside air. Therefore, the air layer inside the through hole 24 (which has a thermal conductivity of about 0.022 kcal/mh°C) can be used as it is as a thermal resistor.

The thermistor 22 is arranged at both opening positions of the through hole 24, and can detect the temperature difference between those positions. This detection output is the lead 2
5 to an electric circuit section (not shown).

In this embodiment, the air layer inside the through hole 24 is used as a thermal resistor, so even if the substrate 21 is made thinner and the air layer becomes thinner, it is not necessary because the thermal conductivity of air is poor. Thermal conductance is sufficient to obtain a suitable detection output. Furthermore, if the substrate 21 is made of a material with high mechanical strength, no problem will arise in terms of strength even if the substrate 21 is made thin.

Note that the size of the thermistor 22 used here is about 3 mm square, and therefore the size of the through hole 24 is 6 to 7 mmφ.

Further, in this embodiment, the thermistor 22 is used as the temperature measuring element, but it is clear that a temperature measuring resistor or a thermopile may be used instead.

As explained above, in this invention, the wafer-shaped thermal resistor material is made hard, and one or more through holes are formed in the thermal resistor along the thickness direction of the thermal resistor. . As a result, even if the thermal resistor is made sufficiently thin, its thermal conductance can be kept sufficiently small, and no problems arise in terms of mechanical strength. Therefore, it is possible to realize a thin wafer-type heat flow sensor that is robust, sensitive, and practical.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view schematically showing a conventional wafer-type heat flow sensor, FIG. 2 is a side view showing a first embodiment of this invention, and FIGS.
6 is a side view showing a modification of the first embodiment, and FIGS. 7 and 8 show a second embodiment of the invention, and FIG. 7 is a cross-sectional view. figure,
FIG. 8 is an exploded perspective view. 11... Hard thin wafer-shaped thermoplastic antibody (wafer), 12... Thermopile, 13... Thermocouple,
14... Covering material, 15... Electric circuit section, 16...
Through hole, 17...cold junction, 18...hot junction, 20
...Resistance temperature detector, 21... Hard thin thermal resistor (substrate), 22... Thermistor, 24... Through hole.

Claims (1)

[Claims for Utility Model Registration] (1) A wafer-shaped thermal resistor, a temperature measuring element that is provided on both sides of the thermal resistor and detects a temperature difference between the two sides, and a temperature measuring element that uses the thermal resistor as a temperature measuring element. In a heat flow sensor consisting of a covering material that covers the same, and an electric circuit section that calculates and displays heat flow density based on the output of the temperature measuring element, the thermal resistor is formed into a hard thin wafer shape, and the thermal resistor is A heat flow sensor characterized by having a through hole penetrating between the front and back surfaces in order to increase the thermal resistance between the front and back surfaces. (2) A utility model registration request in which the temperature measuring element is a thermopile in which contacts are distributed on the front and back surfaces of a thermal resistor, and the through holes are a plurality of through holes provided in the area where the contacts are distributed. A heat flow sensor according to scope 1. (3) Scope of Utility Model Registration Claim 1, where the temperature measuring element is a temperature measuring resistor or a thermistor, and the through holes are a plurality of through holes provided mainly in the temperature measuring region of the temperature measuring resistor or thermistor. The heat flow sensor described. (4) The heat flow sensor according to claim 1, wherein the temperature measuring element is a thermistor, and the through hole is a single through hole that is substantially centered around the thermistor and is sufficiently large for the thermistor.