JP2010223682A - Noncontact type temperature sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a noncontact type temperature sensor with which temperature can be correctly detect even when direct sunlight shines on, by a simple constitution. <P>SOLUTION: The noncontact type temperature sensor 10 is composed of a far-infrared ray receiving part 11 which is disposed inside a transparent plate material and detects far-infrared rays radiated from the transparent plate material, and an operation circuit 13 which computes a detected temperature, based on a detection signal from the far-infrared ray receiving part. The noncontact type temperature sensor 10 is so constituted that it includes a solar radiation sensor 12 which is disposed adjacently to the far-infrared ray receiving part and has almost the same directional characteristics as the receiving part, an amplifying circuit 14 which computes the amount of solar radiation, based on a detection signal from the solar radiation sensor, and a control circuit 15 which outputs a corrected temperature, based on the detected temperature from the operation circuit and the amount of solar radiation from the amplifying circuit. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a non-contact temperature sensor that detects the temperature of a transparent plate such as glass.

Conventionally, a contact temperature sensor and a non-contact temperature sensor are known as methods for detecting the temperature of a glass such as a windshield of an automobile.
The contact-type temperature sensor is directly attached to the glass whose temperature is to be detected, such as a humidity sensor according to Patent Document 1 and a temperature sensor in a vehicle air conditioner.
For this reason, the temperature sensor can be seen from the outside of the glass, and the appearance looks worse. Further, since the temperature sensor is directly attached to the glass, stress acts on the temperature sensor.

On the other hand, the non-contact type temperature sensor 1 as a temperature sensor that does not affect the glass is configured as shown in FIG. 8, for example.
In FIG. 8, the non-contact temperature sensor 1 is configured as a far-infrared sensor arranged inside the glass 2 whose temperature is to be detected.
That is, the non-contact temperature sensor 1 is composed of a far-infrared light receiving unit 3 disposed inside the glass 2 and an arithmetic circuit 4 in more detail.
The far-infrared light receiving unit 3 and the arithmetic circuit 4 are mounted on a circuit board 5.

The far-infrared light receiving unit 3 has a known configuration, detects far-infrared rays emitted from the glass 2, and outputs a detection signal.
Similarly, the arithmetic circuit 4 has a known configuration, performs an operation based on the detection signal from the far-infrared light receiving unit 3, and calculates and outputs a detected temperature To.

The non-contact temperature sensor 1 having such a configuration operates as follows.
First, the far-infrared ray L1 radiated from the glass 2 corresponding to the temperature of the glass 2 enters the far-infrared light receiving unit 3.
As a result, the far-infrared light receiving unit 3 outputs a detection signal corresponding to the intensity of the far-infrared light to the arithmetic circuit 4.

In response to this, the arithmetic circuit 4 performs an operation based on the detection signal from the arithmetic circuit 4, calculates the temperature, that is, the temperature of the far-infrared light receiving unit 3, and the measured temperature of the glass 2, and detects the detected temperature. Output as To.
Thereby, the temperature of the glass 2 can be detected.

In Patent Document 2, a far-infrared detector and a near-infrared detector, a CPU that detects a human body in a monitoring area based on detection signals from these detectors, a temperature sensor that detects an ambient environmental temperature, and a CPU And a temperature setting unit that gives a reference set temperature to the CPU, the CPU operates with the detection signals of both detectors valid when the environmental temperature detected by the temperature sensor is lower than the reference temperature, and the environmental temperature becomes the reference temperature. An infrared human body detection device is disclosed that operates with only the detection signal from the near-infrared detector being valid if it exceeds the limit.
According to such an infrared human body detection device, the human body is not affected by the temperature of the monitoring area, that is, there is no detection failure in summer, and it is not erroneously detected due to snowfall, snow accumulation, or other disturbance light. Can be detected accurately.

JP 2008-094380 A JP-A-10-239450

By the way, in non-contact type temperature sensor 1 mentioned above, when detecting the temperature of the glass which faced the outdoors, such as the windshield of a car, and the window of a house, when sunlight hits the light-receiving part of a far-infrared sensor directly, The measurement temperature To includes a high error.
That is, most of the far infrared rays contained in the sunlight L are reflected or absorbed when passing through the glass, but a part of the far infrared rays L2 are transmitted and enter the far infrared sensor.

Therefore, in addition to the far infrared ray L1 radiated from the glass whose temperature is to be measured, the far infrared ray L2 that passes through the glass is incident on the far infrared sensor. Thereby, the incident light quantity (L1 + L2) of the far infrared rays to the far infrared sensor increases.
For this reason, the detection temperature To calculated by the arithmetic circuit 4 becomes higher, and a higher error is generated by the amount of incident light of the far infrared ray L2 that passes through the glass.

On the other hand, in the infrared human body detection device according to Patent Document 2, when the environmental temperature exceeds the reference temperature, the detection signal from the far infrared detector is invalidated, thereby canceling the detection signal from the near infrared detector. A human body is detected only by the detection signal.
Here, for example, when the ambient temperature is high such as being exposed to direct sunlight, the human body is detected only by the detection signal from the near-infrared detector, that is, by the change of the near-infrared ray. Therefore, the human body can be detected easily and reliably by detecting near infrared rays, but far infrared rays are not detected at all, and therefore, it is unsuitable for detecting temperature, for example.

  In view of the above, an object of the present invention is to provide a non-contact temperature sensor that can accurately detect a temperature even when exposed to direct sunlight with a simple configuration.

  According to the first aspect of the present invention, the object is to provide a far-infrared light receiving unit that is disposed inside the transparent plate and detects far-infrared rays emitted from the transparent plate, and a detection signal from the far-infrared light receiving unit. And a non-contact temperature sensor comprising a calculation circuit for calculating a detected temperature, and being arranged adjacent to the far-infrared light receiving unit and having substantially the same directivity as the far-infrared light receiving unit A correction temperature is calculated and output based on a sensor, an amplification circuit that amplifies a detection signal from the solar radiation sensor to generate a solar radiation amount, a detected temperature from the arithmetic circuit, and a solar radiation amount from the amplifier circuit And a non-contact temperature sensor characterized in that it comprises a control circuit.

In the first aspect, a far infrared ray receiving unit disposed inside a transparent plate material such as glass detects far infrared rays emitted from the transparent plate material. And based on the detection signal from this far-infrared light-receiving part, the said arithmetic circuit calculates detected temperature.
Here, when the direct infrared light hits the far-infrared light receiving part through the transparent plate material, the solar radiation sensor detects the sunlight. And based on the detection signal from this solar radiation sensor, the said amplifier circuit produces | generates the solar radiation amount.
Accordingly, the control circuit refers to the amount of solar radiation from the amplifier circuit, corrects the detected temperature from the arithmetic circuit, and outputs the corrected temperature as a corrected temperature.

Therefore, even if the far-infrared light receiving unit is exposed to direct sunlight through the transparent plate material and the far-infrared light receiving unit also detects far-infrared light by direct sunlight, the addition of far-infrared light by the direct sunlight is It is corrected based on the amount of solar radiation.
As a result, even if the far-infrared light receiving unit is exposed to direct sunlight through the transparent plate material, the control circuit calculates and outputs a true detected temperature that is not affected by direct sunlight.
Thus, according to the non-contact temperature sensor according to the present invention, even if the far-infrared light receiving unit is exposed to direct sunlight, the temperature of the transparent plate material is accurately measured by the far infrared rays radiated from the transparent plate material. be able to.

The non-contact type temperature sensor according to the second aspect of the present invention is the non-contact type temperature sensor according to the first aspect, wherein the control circuit corresponds to the amount of solar radiation from the amplifier circuit, The correction temperature is generated by correcting the detected temperature.
In the second aspect, the detected temperature is corrected in accordance with the amount of solar radiation of direct sunlight, whereby an accurate detected temperature (corrected temperature) is obtained.

The non-contact temperature sensor according to a third aspect of the present invention is the non-contact temperature sensor according to the first or second aspect, wherein the solar radiation sensor is a near infrared sensor.
In this third aspect, the solar radiation sensor outputs a detection signal corresponding to the amount of solar radiation by receiving a near infrared component in direct sunlight. Here, the wavelength of this near infrared ray component is different from that of the far infrared ray emitted from the transparent plate material. Accordingly, it is possible to calculate an accurate amount of solar radiation, and furthermore, the detected temperature is corrected with high accuracy, and a more accurate detected temperature (corrected temperature) can be obtained.

Thus, according to the non-contact temperature sensor of the present invention, even if the far-infrared light receiving unit is exposed to direct sunlight through the transparent plate material, only the amount of solar radiation by this direct sunlight is obtained by the solar sensor and the amplification circuit. Generated.
Thereby, the said control circuit correct | amends the detection temperature calculated by the said far-infrared light-receiving part and the calculating circuit based on this solar radiation amount. Therefore, since the influence of direct sunlight can be eliminated and an accurate detected temperature (corrected temperature) can be generated, the exact temperature of the transparent plate can be measured even when exposed to direct sunlight.

  As described above, according to the present invention, it is possible to provide a non-contact temperature sensor with a simple configuration that can accurately detect a temperature even when exposed to direct sunlight.

It is a block diagram which shows the structure of one Embodiment of the non-contact-type temperature sensor by this invention. It is a schematic perspective view which shows the far-infrared light-receiving part and solar radiation sensor in the non-contact-type temperature sensor of FIG. It is the schematic which shows the example of the installation of the far-infrared light-receiving part and solar radiation sensor of FIG. It is a graph which shows the radiant energy characteristic of the far infrared rays from a windshield, and the light reception sensitivity characteristic by the solar radiation sensor of FIG. It is a graph which shows the temperature detection error according to temperature by the far infrared rays light-receiving part of FIG. It is a graph which shows the approximate inclination in the temperature detection error according to temperature of FIG. It is a graph which shows the temperature detection error according to temperature after correction | amendment by the control circuit in the non-contact-type temperature sensor of FIG. It is the schematic which shows the structure of an example of the conventional non-contact-type temperature sensor.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. 1 to 7.
The embodiments described below are preferable specific examples of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention particularly limits the present invention in the following description. As long as there is no description of the effect, it is not restricted to these aspects.

FIG. 1 shows a configuration of an embodiment of a non-contact temperature sensor according to the present invention.
In FIG. 1, the non-contact temperature sensor 10 includes a far-infrared light receiving unit 11, a solar radiation sensor 12, an arithmetic circuit 13, an amplifier circuit 14, and a control circuit 15.

The far-infrared light receiving unit 11 is composed of, for example, a far-infrared sensor having a known configuration, like the far-infrared light receiving unit 3 in the conventional non-contact temperature sensor 1 shown in FIG. It is arrange | positioned inside the windshield (after-mentioned).
Thereby, the far-infrared light-receiving part 11 receives the far-infrared L1 radiated | emitted from a windshield, and outputs the detection signal according to the light quantity.

The solar radiation sensor 12 is composed of a near-infrared sensor having substantially the same directivity as the far-infrared light receiving unit 11, for example, a photodiode.
And the said solar radiation sensor 12 is arrange | positioned adjacent to the far-infrared light-receiving part 11 mentioned above.
Thereby, the said solar radiation sensor 12 has a low sensitivity with respect to the far infrared rays L1 radiated | emitted from glass, and has a high sensitivity with respect to the direct sunlight which permeate | transmits and injects through glass.

As shown in FIG. 2, the far-infrared light receiving unit 11 and the solar radiation sensor 12 are integrally configured as a light receiving unit 16.
The light receiving unit 16, that is, the far-infrared light receiving unit 11 and the solar radiation sensor 12 are installed inside the windshield 21 of the automobile 20, for example, in the vicinity of the windshield 21 in the illustrated case, as shown in FIG. It is arranged on the ment panel 22.

Here, the radiant energy characteristic of the windshield 21 and the light receiving sensitivity characteristic of the solar radiation sensor 12 are as shown in the graph of FIG.
That is, the radiant energy characteristics of the windshield 21 in FIG. 4 are indicated by reference sign A1 (glass temperature −20 ° C.), reference sign A2 (glass temperature 0 ° C.), reference sign A3 (glass temperature 20 ° C.), reference sign A4 (glass temperature 40 ° C.). ), A5 (glass temperature 60 ° C.), A6 (glass temperature 80 ° C.), A7 (glass temperature 100 ° C.), A8 (glass temperature 120 ° C.), a high energy value in the far infrared region. It can be seen that it has an energy value corresponding to the glass temperature.

In addition, the light reception sensitivity characteristic of the solar radiation sensor 12 has sensitivity in the near infrared region as indicated by a symbol B in FIG. 4, and the wavelength is completely different from the radiant energy characteristic of the windshield 21.
Thereby, the solar radiation sensor 12 can detect only the direct sunlight (sunlight) without being affected by the far infrared rays emitted from the windshield 21.

  Similar to the arithmetic circuit 4 in the conventional non-contact temperature sensor 1 shown in FIG. 8, the arithmetic circuit 13 calculates based on the detection signal from the far-infrared light receiving unit 11 to calculate the detected temperature To. To do.

  The amplification circuit 14 amplifies the detection signal from the solar radiation sensor 12 to generate the solar radiation amount Is.

  Based on the detected temperature To from the arithmetic circuit 13 and the amount of solar radiation Is from the amplifier circuit 14, the control circuit 15 calculates and outputs a correction temperature Dt2 that eliminates the influence of direct sunlight, that is, the glass temperature Tg.

The correction calculation of the detected temperature To by the control circuit 15 will be described below.
That is, in general, between the radiant energy E of the black body and the thermodynamic temperature T,
(Equation 1) E = σT ⁴ (Stephan-Boltzmann radiation law)
Holds.
Therefore, the energy radiated from the windshield 21 to be temperature-measured is Eg, the far-infrared light energy passing through the windshield 21 that is an error is Es, the true glass temperature is Tg, and the temperature detection error due to sunlight is If Ts,
(Equation 2) Eg + Es = σ (Tg + Ts) ⁴
It becomes.
Solving this equation for the temperature detection error Ts,
(Equation 3) Ts = {(Eg + Es) / σ} ⁻⁴ −Tg
It becomes.
According to this formula, when the glass temperature Tg is −20 ° C., 0 ° C., 20 ° C., 40 ° C., 60 ° C., 80 ° C., 100 ° C., the signs A1, A2, A3, A4, A5 in the graph of FIG. It is expressed as shown by A6 and A7.
When the slope of the temperature detection error Ts for each temperature is obtained from the graph of FIG. 5, it can be seen that the temperature detection error Ts is larger as the glass temperature Tg is lower, as shown in FIG.

In order to linearly approximate the graph of FIG. 6, the correction coefficient β for correcting the temperature detection error Ts is:
(Equation 4) β = aTo ² −bTo + c (To is the detected temperature, a, b, c are constants)
Is required.
Therefore, using this correction coefficient β, from the detected temperature To obtained from the far-infrared light receiving unit 11 and the arithmetic circuit 13, the true glass temperature Tg is
(Equation 5) Tg = To−β × Is (Is is the amount of solar radiation)
Is obtained.

The non-contact temperature sensor 10 according to the present invention is configured as described above and operates as follows.
That is, the far-infrared light receiving unit 11 disposed inside the windshield 21 of the automobile 20 receives far-infrared radiation emitted from the windshield 21 and outputs a detection signal to the arithmetic circuit 13.
On the other hand, the solar radiation sensor 12 receives direct sunlight that is transmitted through the windshield 21 and outputs a detection signal to the amplifier circuit 14.

  Thereby, the arithmetic circuit 13 calculates the detection temperature To based on the detection signal from the far-infrared light receiving unit 11, and the amplification circuit 14 amplifies the detection signal from the solar sensor 12 to generate the solar radiation amount Is. To do.

  Then, the control circuit 15 calculates the true glass temperature (corrected temperature) Tg by performing the calculation according to the above formula 5 based on the glass temperature To from the calculation circuit 13 and the solar radiation amount Is from the amplification circuit 14. .

In this way, with respect to the true correction temperature Tg output from the control circuit 15, the influence of direct sunlight is almost completely eliminated with respect to the temperature detection error Ts at each temperature, as indicated by the symbol A in the graph of FIG. Will be.
Therefore, according to the non-contact temperature sensor 10 according to the present invention, even if the far-infrared light receiving unit 11 is exposed to direct sunlight through the windshield 21 of the automobile 20, it is not affected by the direct sunlight. It becomes possible to measure the true glass temperature (that is, the correction temperature) Tg.

  Thus, according to the present invention, it is possible to provide an extremely excellent non-contact type temperature sensor that can accurately detect the temperature even with direct sunlight by a simple configuration. it can.

  In the above-described embodiment, a photodiode is used as the near-infrared sensor that constitutes the solar radiation sensor 12. However, the present invention is not limited to this. Obviously, a near-infrared sensor having sensitivity only to sunlight may be used.

  Moreover, in embodiment mentioned above, although the case of the windshield 21 of the motor vehicle 20 was demonstrated as a transparent board | plate material which should detect temperature, if it is transparent board | plate materials, such as not only this but glass used outdoors, a building It may be a non-contact temperature sensor for measuring the temperature of the window glass or the like.

  Furthermore, in the above-described embodiment, the case of glass has been described as the transparent plate material whose temperature is to be detected. However, the present invention is not limited thereto, and is not a contact type for measuring the temperature of a transparent plate material such as plastic other than glass. It may be a temperature sensor.

DESCRIPTION OF SYMBOLS 10 Non-contact-type temperature sensor 11 Far-infrared light-receiving part 12 Solar radiation sensor 13 Arithmetic circuit 14 Amplification circuit 15 Control circuit 16 Light-receiving unit 20 Car 21 Windshield 22 Instrument panel

Claims (3)

A far-infrared light receiving unit that is disposed inside the transparent plate and detects far-infrared rays emitted from the transparent plate, and an arithmetic circuit that calculates a detection temperature based on a detection signal from the far-infrared light receiving unit. A non-contact temperature sensor,
Furthermore, a solar radiation sensor that is arranged adjacent to the far-infrared light receiving section and has substantially the same directivity as the far-infrared light receiving section, and an amplification circuit that amplifies a detection signal from the solar radiation sensor and generates a solar radiation amount And a control circuit that calculates and outputs a correction temperature based on the detected temperature from the arithmetic circuit and the amount of solar radiation from the amplifier circuit.   2. The non-contact temperature according to claim 1, wherein the control circuit generates a corrected temperature by correcting the detected temperature from the arithmetic circuit in accordance with the amount of solar radiation from the amplifier circuit. Sensor. The non-contact type temperature sensor according to claim 1, wherein the solar radiation sensor is a near infrared sensor.

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