JP2006292438A - Temperature detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive temperature detection device having excellent responsiveness and accuracy of temperature detection. <P>SOLUTION: In this temperature detection device 10, a temperature detection element 11 is equipped in a casing 110 with a substrate 120, the first optical system 131, the second optical system 132, the first Si photodiode 141, the second Si photodiode 142 and a signal processing part 150. The signal processing part 150 inputs a current signal output from each of the Si photodiodes 141, 142, outputs a voltage signal having a value corresponding to the value of the current signal, and includes a sensitivity adjusting means for adjusting the relationship of an output voltage value with an input current value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a temperature detection device that detects the temperature of an object to be measured based on thermal radiation radiated from the object to be measured.

  Various temperature detection devices are known. For example, in addition to a contact temperature detection device including a temperature detection element such as a thermocouple or a thermistor, a non-contact temperature detection device is also known. The contact-type temperature detection device is provided with the temperature detection element in direct contact with the measurement object, and it is assumed that the temperature detection element has the same temperature as the measurement object. The response is poor. On the other hand, the non-contact type temperature detecting device detects the temperature of the measurement object based on the thermal radiation radiated from the measurement object, and the light receiving element that receives the thermal radiation contacts the measurement object. Therefore, the response to the temperature change of the measurement object is good.

  As described in Patent Document 1, the non-contact type temperature detection device is, for example, a cooking heater device including an electric heating unit that heats an object to be heated (such as a pan or a frying pan). Used when detecting. In the cooking heater device described in this document, an object to be heated is placed on a top plate made of heat-resistant tempered glass, and a magnetic field generating coil and a temperature detection device are provided under the top plate. When a high-frequency alternating current flows through the magnetic field generating coil, an induced current flows through the object to be heated by electromagnetic induction, and the object to be heated itself generates heat. And based on the thermal radiation radiated | emitted from the to-be-heated to-be-heated object, the temperature of a to-be-heated object is detected by the temperature detection apparatus.

  Thus, by using a non-contact type temperature detection device in the cooking heater device, temperature detection can be performed with high responsiveness to the temperature change of the object to be heated, which is the measurement object, and as a result, the temperature can be detected at high speed. Since the temperature of the heated object can be electrically controlled, for example, when the content of the object to be heated is tempura oil, ignition of the tempura oil can be prevented.

In addition, such a non-contact type temperature detecting device generally includes two light receiving elements as described in Patent Document 1. That is, in a black body, which is a virtual object that radiates thermal radiation most efficiently, the wavelength dependence and temperature dependence of thermal radiation follow Planck's equation. On the other hand, the heat radiation from the object to be heated which is an actual object is smaller than the heat radiation from the black body, and the emissivity (ratio to the heat radiation from the black body) differs depending on the material of the object to be heated. Therefore, by detecting the thermal radiation at each of the two wavelengths by the two light receiving elements having different spectral sensitivity characteristics by the wavelength selection filter, the influence due to the difference in emissivity of the object to be heated is reduced, and the temperature The measurement accuracy is improved. Patent Document 1 exemplifies InGaAs (indium gallium arsenide), PbS (lead sulfide), PbSe (lead selenide), and the like as light receiving elements included in the temperature detection device.
JP 2003-109736 A

  Although the contact-type temperature detection device is inexpensive, the temperature measurement response is poor. On the other hand, the non-contact type temperature detection device as described in Patent Document 1 is expensive because it uses InGaAs or the like as a light receiving element, although it has good temperature measurement responsiveness. Although it is desired to realize a temperature detection device with good temperature response and low cost, such a device is not known at present.

  A Si photodiode is known as an inexpensive light receiving element. However, compared with InGaAs photodiodes, Si photodiodes are less sensitive to thermal radiation detection, and when used for temperature detection at several hundred degrees Celsius, there are large variations in temperature detection between individuals, and temperature detection accuracy is poor. Therefore, it has not been conventionally used in a non-contact type temperature detecting device.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an inexpensive temperature detection device with excellent temperature response and accuracy.

  A temperature detection device according to the present invention is a temperature detection device that detects the temperature of an object to be measured based on thermal radiation radiated from the object to be measured, and (1) has a first spectral sensitivity characteristic. A first Si photodiode that outputs a current signal having a value corresponding to the amount of incident thermal radiation based on the first spectral sensitivity characteristic; and (2) a second spectral sensitivity characteristic different from the first spectral sensitivity characteristic. A second Si photodiode that outputs a current signal having a value corresponding to the amount of incident thermal radiation based on the second spectral sensitivity characteristic; and (3) a current signal output from the first Si photodiode is input, and this current signal is input. A first signal processing circuit that outputs a voltage signal of a value corresponding to the value of (4), and (4) a current signal output from the second Si photodiode is input, and a voltage signal of a value corresponding to the value of this current signal is output A second signal processing circuit It is characterized by. Further, the first signal processing circuit includes a first sensitivity adjusting unit that adjusts a relationship between the output voltage value and the input current value, and the second signal processing circuit is a second signal that adjusts the relationship between the output voltage value and the input current value. It includes a sensitivity adjusting means. In addition, the temperature detection device according to the present invention preferably further includes a calculation unit that obtains the temperature of the measurement object based on the value of the voltage signal output from each of the first signal processing circuit and the second signal processing circuit. is there.

  In the temperature detection device according to the present invention, the thermal radiation radiated from the measurement object is incident on the first Si photodiode and the second Si photodiode having different spectral sensitivity characteristics. The current signal output from the first Si photodiode has a value corresponding to the first spectral sensitivity characteristic of the first Si photodiode, and is input to the first signal processing circuit and converted into a voltage signal. The current signal output from the second Si photodiode has a value corresponding to the second spectral sensitivity characteristic of the second Si photodiode, and is input to the second signal processing circuit and converted into a voltage signal. . At this time, in the first signal processing circuit, the relationship of the output voltage value to the input current value (that is, the temperature detection sensitivity) is adjusted by the first sensitivity adjusting means, and the output voltage value relative to the input current value in the second signal processing circuit. (Ie, temperature detection sensitivity) is adjusted by the second sensitivity adjusting means. Then, based on the value of the voltage signal output from each of the first signal processing circuit and the second signal processing circuit, the temperature of the measurement object is obtained in the calculation unit. Therefore, the temperature detection device according to the present invention is non-contact type and can detect the temperature with good responsiveness, and is inexpensive because the Si photodiode is used as the light receiving element. Since the processing circuit includes the first sensitivity adjustment unit and the second signal processing circuit includes the second sensitivity adjustment unit, the accuracy of temperature detection is improved.

  The first signal processing circuit includes: a first current-voltage conversion circuit that converts an input current signal into a voltage signal; a first amplification circuit that amplifies and outputs a voltage signal output from the first current-voltage conversion circuit; Preferably, the first sensitivity adjusting means includes means for adjusting the amplification factor of the first amplifier circuit. The second signal processing circuit includes a second current-voltage conversion circuit that converts the input current signal into a voltage signal, and a second amplification that amplifies and outputs the voltage signal output from the second current-voltage conversion circuit. It is preferable to include a circuit and means for adjusting the amplification factor of the second amplifier circuit as the second sensitivity adjusting means. In this case, in each of the first signal processing circuit and the second signal processing circuit, the current signal output from the corresponding Si photodiode is converted into a voltage signal by the current-voltage conversion circuit, and the voltage signal is amplified by the amplifier circuit. Is output. The temperature detection sensitivity can be adjusted by adjusting the amplification factor of the amplifier circuit.

  In the temperature detection device according to the present invention, the first Si photodiode and the second Si photodiode have different light detection regions, and heat radiation radiated from a certain range on the surface of the measurement object is guided to the first Si photodiode. It is preferable to further include one optical system and a second optical system that guides thermal radiation radiated from the predetermined range to the second Si photodiode. In this case, thermal radiation radiated from a certain range of the surface of the measurement object is guided to each of the first Si photodiode and the second Si photodiode by the corresponding optical system, so that the temperature of the measurement object can be accurately determined. Can be detected.

  The first Si photodiode and the second Si photodiode may be separate from each other, but are preferably formed on a common Si substrate. In the latter case, it is preferable that the temperature detection device further includes an optical system that guides the thermal radiation radiated from a certain range of the surface of the measurement object to the first Si photodiode and the second Si photodiode. Since it can be assembled as the same package, it is easy to assemble and can be made small.

  The temperature detection device according to the present invention has a light detection region in which the first Si photodiode and the second Si photodiode overlap each other, and heat radiation radiated from a certain range of the surface of the measurement object is transmitted to the first Si photodiode and the second Si photodiode. It is preferable to further include an optical system that leads to the photodiode. In this case, since the optical system can be assembled coaxially, the apparatus can be easily assembled.

  The first Si photodiode and the second Si photodiode may be separate from each other, but are preferably arranged on a common circuit board. In the latter case, it is preferable that the temperature detection device further includes an optical system that guides the thermal radiation radiated from a certain range of the surface of the measurement object to the first Si photodiode and the second Si photodiode. Since it can be assembled as the same package, it is easy to assemble and can be made small.

  Since the temperature detection device according to the present invention is a non-contact type, it can detect the temperature with good responsiveness and is inexpensive because it uses a Si photodiode as the light receiving element. Further, since each of the first signal processing circuit and the second signal processing circuit includes a sensitivity adjustment unit, the accuracy of temperature detection is improved.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a cross-sectional view of a main part of a cooking heater device 1 including a temperature detection device 10 according to the present embodiment. The cooking heater device 1 includes a temperature detection device 10, a top plate 20, a magnetic field generating coil 30, and a power supply circuit 40, and heats an object to be heated 2 (for example, a pan or a frying pan) placed on the top plate 20. Then, the thing in the to-be-heated material 2 is heated and cooked.

  The temperature detection device 10, the magnetic field generation coil 30, and the power supply circuit 40 are disposed below the top plate 20. When a high-frequency alternating current supplied from the power supply circuit 40 flows to the magnetic field generating coil 30, an induced current flows to the bottom of the object to be heated 2 due to electromagnetic induction by the magnetic field lines M generated from the magnetic field generating coil 30. The heated object 2 generates heat due to the electric resistance of 2. Then, the heat radiation radiated from the heated object 2 that has generated heat passes through the window portion 21 provided on the top plate 20 and reaches the temperature detection element 11 of the temperature detection device 10, and is heated by the temperature detection device 10. The temperature of the object 2 is detected. The position where the window portion 21 and the temperature detecting element 11 are provided may be on the center line of the magnetic field generating coil 30 or may be in the vicinity where the conducting wire of the magnetic field generating coil 30 deviates from the center line. Good.

  The temperature detection device 10 includes a temperature detection element 11 and a calculation unit 12. The temperature detection element 11 is disposed below the window portion 21 of the top plate 20, receives heat radiation radiated from the bottom of the heated object 2 to be measured and transmitted through the window portion 21, and the light reception result is received. The voltage signal to be expressed is output to the calculation unit 12. The calculation unit 12 receives the voltage signal output from the temperature detection element 11 and obtains the temperature of the object to be heated 2 based on the value of the voltage signal. When calculating the temperature of the object to be heated 2 from the input voltage value in the calculation unit 12, the relationship between the two measured and stored in advance is referred to.

  Moreover, the calculating part 12 controls the power supply circuit 40 based on the calculated | required temperature. For example, when the calculation unit 12 determines that the obtained temperature exceeds a predetermined temperature, the calculation unit 12 adjusts the magnitude of the alternating current supplied from the power supply circuit 40 to the magnetic field generating coil 30, or generates a magnetic field. The supply of alternating current to the coil 30 is stopped. The calculation unit 12 may display the obtained temperature on a display unit (not shown), or generate a warning when determining that the obtained temperature exceeds a predetermined temperature. May be.

  FIG. 2 is a cross-sectional view of the temperature detection element 11 of the temperature detection apparatus 10 according to the present embodiment. The temperature detection device 10 includes a substrate 120, a first optical system 131, a second optical system 132, a first Si photodiode 141, a second Si photodiode 142, and a signal processing unit 150 in a housing 110 in the temperature detection element 11. Prepare. A first Si photodiode 141 and a second Si photodiode 142 are fixed to the upper surface of the substrate 120 (the surface on the heated object 2 side). A first optical system 131 and a second optical system 132 are disposed above the substrate 120. A signal processing unit 150 is provided on the lower surface of the substrate 120.

  The first optical system 131 guides thermal radiation radiated from a certain range at the bottom of the object to be heated 2 to the first Si photodiode 141. Similarly, the second optical system 132 guides thermal radiation radiated from a certain range at the bottom of the object to be heated 2 to the second Si photodiode 142. Each of the first optical system 131 and the second optical system 132 is specifically a convex lens, and guides heat radiation radiated from a common fixed range at the bottom of the object to be heated 2 to the corresponding Si photodiode. . Therefore, it is preferable that the optical axes of the first optical system 131 and the second optical system 132 are inclined by a predetermined angle with respect to the vertical line of the top plate 20.

  The first Si photodiode 141 has a first spectral sensitivity characteristic, and outputs a current signal having a value corresponding to the incident amount of thermal radiation based on the first spectral sensitivity characteristic. The second Si photodiode 142 has a second spectral sensitivity characteristic, and outputs a current signal having a value corresponding to the incident amount of thermal radiation based on the second spectral sensitivity characteristic. The first spectral sensitivity characteristic of the first Si photodiode 141 and the second spectral sensitivity characteristic of the second Si photodiode 142 are different from each other. In order to make the spectral sensitivity characteristics of the two Si photodiodes 141 and 142 different from each other, a wavelength selection filter may be provided in front of the light receiving surface of each Si photodiode. The depths may be different from each other.

  The signal processing unit 150 provided on the lower surface of the substrate 120 is electrically connected to each of the Si photodiodes 141 and 142 provided on the upper surface of the substrate 120 by through electrodes provided on the substrate 120. The signal processing unit 150 receives current signals output from the Si photodiodes 141 and 142, and outputs voltage signals having values corresponding to the values of the current signals.

  The board 120 further includes a connector (not shown) for sending the voltage signal output from the signal processing unit 150 to the arithmetic unit 12, and a screw hole (not shown) for fixing the board 120 to the housing 110. Is provided.

  The casing 110 is preferably made of a material having high thermal conductivity (for example, Al die cast). Since the Si photodiodes 141 and 142 and the signal processing unit 150 are housed in the casing 110 made of a material having a high thermal conductivity in this manner, these temperatures become substantially equal, and temperature correction described later is performed. Convenient above.

  FIG. 3 is a configuration diagram of the signal processing unit 150 of the temperature detection device 10 according to the present embodiment. The signal processing unit 150 includes a first signal processing circuit 151 and a second signal processing circuit 152. The first signal processing circuit 151 receives the current signal output from the first Si photodiode 141 and outputs a voltage signal having a value corresponding to the value of the current signal. The first signal processing circuit 151 receives the current signal output from the first Si photodiode 141. A current-voltage conversion circuit that converts the current signal into a voltage signal, and an amplification circuit that amplifies and outputs the voltage signal output from the current-voltage conversion circuit. Similarly, the second signal processing circuit 152 receives the current signal output from the second Si photodiode 142 and outputs a voltage signal having a value corresponding to the value of the current signal. The second Si photodiode A current-voltage conversion circuit that converts the current signal input from 142 into a voltage signal, and an amplification circuit that amplifies and outputs the voltage signal output from the current-voltage conversion circuit.

  Each of the first signal processing circuit 151 and the second signal processing circuit 152 includes a sensitivity adjustment unit that adjusts the relationship of the output voltage value with respect to the input current value. Specifically, as the sensitivity adjustment unit, the amplification of each amplifier circuit It is preferred to include means for adjusting the rate.

  The first signal processing circuit 151 includes first temperature correction means for correcting fluctuations in the first spectral sensitivity characteristic due to temperature changes of the first Si photodiode 141. Specifically, the first temperature correction means. The amplifier circuit preferably includes a resistor whose resistance value varies with temperature. Similarly, the second signal processing circuit 152 includes a second temperature correction unit that corrects the variation in the second spectral sensitivity characteristic due to the temperature change of the second Si photodiode 142, and specifically, this second temperature correction. As a means, the amplifier circuit preferably includes a resistor whose resistance value varies with temperature.

  FIG. 4 is a circuit diagram of the first signal processing circuit 151 of the temperature detection device 10 according to the present embodiment. In the following, the circuit configuration of the first signal processing circuit 151 will be described, but the circuit configuration of the second signal processing circuit 152 is the same. The first signal processing circuit 151 includes a current-voltage conversion circuit 161, a low-pass filter 162, an amplifier circuit 163, and a low-pass filter 164.

The current-voltage conversion circuit 161 receives the current signal output from the first Si photodiode 141, converts the current signal into a voltage signal, and outputs the voltage signal to the low-pass filter 162. The current-voltage conversion circuit 161 includes an amplifier A ₁ , a resistor R _1, and a capacitive element C ₁ . The non-inverting input terminal of the amplifier A ₁ is grounded, and the inverting input terminal of the amplifier A ₁ is connected to the first Si photodiode 141. The resistor R ₁ and the capacitive element C ₁ are connected in parallel to each other and provided between the inverting input terminal and the output terminal of the amplifier A ₁ .

Low pass filter 162 includes a resistor _{R 2} and capacitor element _{C 2.} One end of the resistor R ₂ is connected to the output terminal of the amplifier A ₁ of the current-voltage conversion circuit 161. The other end of the resistor R ₂ is connected to the non-inverting input terminal of the amplifier A ₃ of the amplifier circuit 163. Capacitive element C ₂ is provided between the other end of the resistor R ₂ and the constant voltage point.

The amplifier circuit 163 receives the voltage signal output from the current-voltage conversion circuit 161 and passed through the low-pass filter 162, amplifies the voltage signal, and outputs the amplified voltage signal to the low-pass filter 164. The amplifier circuit 163 includes an amplifier A ₃ , resistors R _{31 to} R _33, and a capacitive element C ₃ . The resistor R ₃₂ and the resistor R ₃₃ are connected in series, and the resistors R ₃₂ and R ₃₃ and the capacitive element C ₃ are connected in parallel to each other, and the inverting input terminal and the output terminal of the amplifier A ₃ are connected to each other. It is provided between. Resistor R ₃₁ is provided between the inverting input terminal of the amplifier A ₃ and constant voltage point.

Resistor R ₃₁ is a heat-sensitive resistor whose resistance value changes with temperature, a large resistance value higher temperatures. The resistor R ₃₂ has a fixed resistance value. The resistor R ₃₃ has a variable resistance value. When the resistance value of the resistor _{R 31} represents a _{R 31,} the resistance value of the resistor _{R 32} represents a _{R 32,} also the resistance value of the resistor _{R 33} and is represented as _{R 33,} the amplification factor of the amplifier circuit 163 G is represented by the following formula (1).

G = 1 + (R ₃₂ + R ₃₃ ) / R ₃₁ (1)

The resistor R ₃₃ can adjust the amplification factor G of the amplifier circuit 163 by adjusting its resistance value, and thus can function as the sensitivity adjusting means described above. Further, the resistor R ₃₁ is the resistance value with temperature changes, thereby, it is possible to correct the gain G of the amplifier circuit 163 may act as a temperature compensation means described above.

Low pass filter 164 includes a resistor _{R 4} and the capacitor _{C 4.} One end of the resistor R ₄ is connected to the output terminal of the amplifier A ₃ of the amplifier circuit 163. The other end of the resistor R ₃ is connected to the calculation unit 12. Capacitive element C ₄ is provided between the other end and the ground potential of the resistor R _4.

Resistor R ₀₁ and resistor R ₀₂ are connected in series. One end of the resistor R ₀₁ is the power supply voltage Vcc is applied, one end of the resistor R ₀₂ is grounded. A capacitive element C ₀ is provided in parallel with the resistor R ₀₂ . The connection point between the resistor R ₀₁ and the resistor R ₀₂ is a constant voltage obtained by dividing the power supply voltage Vcc, is connected to one end of the capacitive element C ₂ of the low-pass filter 162, and is connected to the resistance of the amplifier circuit 163. with one end of the vessel _{R 31} are connected. The power supply voltage Vcc, for example, is supplied from the arithmetic unit 12 via the connector on the board 120 of the temperature detecting element 11, also it is applied to the capacitor C ₂ and a resistor R ₃₁ each end through a low pass filter The The power supply voltage Vcc is also supplied to each of the amplifier A ₁ of the current-voltage conversion circuit 161 and the amplifier A ₃ of the amplifier circuit 163.

An example of specific characteristic values of each element included in the first signal processing circuit 151 is as follows. Current - resistance value of the resistor _{R 1} included in the voltage conversion circuit 161 is 22Emuomega, capacitance of the capacitor _{C 1} is 10 pF. Resistance value of the resistor _{R 2} that is included in the low-pass filter 162 is a 10 k.OMEGA, capacitance of the capacitor _{C 2} is 0.1ĩF. Resistance value of the resistor _{R 31} included in the amplifier circuit 163 is 1 k [Omega, resistor resistance of _{R 32} is 22Keiomega, maximum resistance value of the resistor _{R 33} is 100 k.OMEGA, the capacitance of the capacitor _{C 3} Is 0.1 μF. The resistance value of the resistor _{R 4} contained in the low-pass filter 164 is 1.8Keiomega, capacitance of the capacitor _{C 4} is 0.1ĩF. The resistance value of the resistor R ₀₁ is 43 kΩ, the resistance value of the resistor R ₀₂ is 10 kΩ, and the capacitance value of the capacitive element C ₀ is 0.1 μF.

  FIG. 5 is a diagram illustrating an example of a cross section of the first Si photodiode 141 and the second Si photodiode 142 of the temperature detection device 10 according to the present embodiment.

  In the example shown in FIG. 5A, the p region 211 and the p region 212 are formed on the n region 210. Each region is made of a Si semiconductor. The p region 211 is formed deeper than the p region 212. The first Si photodiode 141 includes a pn junction between the n region 210 and the p region 211. The second Si photodiode 142 includes a pn junction between the n region 210 and the p region 212. The thermal radiation radiated from the heated object is in the infrared region with a wavelength of about 1 μm to several μm, and short wavelength infrared light is more easily absorbed by the Si semiconductor than the long wavelength. Therefore, the first Si photodiode 141 having a relatively deep pn junction generates charges in response to heat radiation having a relatively long wavelength, whereas the second Si photodiode 142 having a relatively shallow pn junction is Charges are generated in response to heat radiation with a relatively short wavelength. As described above, the first spectral sensitivity characteristic of the first Si photodiode 141 and the second spectral sensitivity characteristic of the second Si photodiode 142 are different from each other by making the depths of the pn junctions different from each other. Become.

In the example shown in FIG. 5B, the p region 221 and the p region 222 are formed on the n region 220, and the n ⁺ region 223 is provided between the n region 220 and the p region 222. Each region is made of a Si semiconductor. The depth of the p region 221 is approximately the same as the depth of the p region 222. The first Si photodiode 141 includes a pn junction between the n region 220 and the p region 221. The second Si photodiode 142 includes a pn junction between the n ⁺ region 223 and the p region 222. The pn junction of the second Si photodiode 142 is formed at a position shallower than the pn junction of the first Si photodiode 141 by providing the n ⁺ region 223. Therefore, the first Si photodiode 141 having a relatively deep pn junction generates charges in response to heat radiation having a relatively long wavelength, whereas the second Si photodiode 142 having a relatively shallow pn junction is Charges are generated in response to heat radiation with a relatively short wavelength. Thus, by providing the n ⁺ region 223 on one side, the first spectral sensitivity characteristic of the first Si photodiode 141 and the second spectral sensitivity characteristic of the second Si photodiode 142 become different from each other.

In the example shown in FIG. 5C, an n ⁺ region 231 is formed so as to be embedded in the p region 230, and an n ⁺ region 232 is formed on the p region 230. Each region is made of a Si semiconductor. The first Si photodiode 141 includes a pn junction between the p region 230 and the n ⁺ region 231. The second Si photodiode 142 includes a pn junction between the p region 230 and the n ⁺ region 232. When heat radiation enters the n ⁺ region 232 from above, the second Si photodiode 142 having a relatively shallow pn junction generates charges in response to heat radiation having a relatively short wavelength, whereas the pn junction The first Si photodiode 141 having a relatively deep depth generates charges in response to heat radiation having a relatively long wavelength that has been transmitted therethrough. As described above, when the two junctions have a laminated structure, the first spectral sensitivity characteristic of the first Si photodiode 141 and the second spectral sensitivity characteristic of the second Si photodiode 142 are different from each other. .

  In the example shown in FIG. 5D, an n region 241 is provided on the p region 240, and a p region 242 is provided on the n region 241. The first Si photodiode 141 includes a pn junction between the p region 240 and the n region 241. The second Si photodiode 142 includes a pn junction between the p region 242 and the n region 241. The pn junction of the second Si photodiode 142 is formed at a shallower position than the pn junction of the first Si photodiode 141. Therefore, the first Si photodiode 141 having a relatively deep pn junction generates charges in response to heat radiation having a relatively long wavelength, whereas the second Si photodiode 142 having a relatively shallow pn junction is Charges are generated in response to heat radiation with a relatively short wavelength. As described above, the first spectral sensitivity characteristic of the first Si photodiode 141 and the second spectral sensitivity characteristic of the second Si photodiode 142 are different from each other by changing the depth of the pn junction. .

  In the examples shown in FIGS. 5A and 5B, the two Si photodiodes 141 and 142 are arranged side by side as shown in FIG. Have. On the other hand, in the example shown in FIGS. 5C and 5D, the two Si photodiodes 141 and 142 are arranged vertically and overlap each other, unlike the one shown in FIG. Therefore, it is only necessary to provide one optical system that guides the heat radiation radiated from a certain range of the surface of the object to be heated 2 to the Si photodiodes 141 and 142. In addition, it is preferable that the two Si photodiodes 141 and 142 are formed on a common Si substrate as in the examples shown in FIGS. 5A and 5B in terms of miniaturization. However, they may be separate from each other. It is also preferable that the two Si photodiodes 141 and 142 are formed on a common circuit board.

FIG. 6 is a diagram showing black body radiation characteristics, Si photodiode sensitivity characteristics, and InGaAs photodiode sensitivity characteristics. In this figure, as black body radiation characteristics, black body radiation characteristics M _{1 at} a temperature of 538K, black body radiation characteristics M _{2 at} a temperature of 573K, black body radiation characteristics M _{3 at} a temperature of 598K, and temperature blackbody radiation characteristic _{M 4} in the case of 623K is shown. As the sensitivity characteristic of the Si photodiode, Si photodiode sensitivity characteristics S ₁ of the type S _1, and the sensitivity characteristics S ₂ of Si photodiode type S ₂ having different spectral sensitivity characteristics of a type S ₁ is shown Has been. Further, as the sensitivity characteristic of the InGaAs photodiode, the sensitivity characteristics _{G 1} of InGaAs photodiode type _{G 1,} and the sensitivity characteristic of the InGaAs photodiode type _{G 2} having different spectral sensitivity characteristics of a type _{G 1 G 2} It is shown.

  As described above, black body radiation is thermal radiation from a black body, which is a virtual object that radiates thermal radiation most efficiently, and the wavelength dependence and temperature dependence of the thermal radiation follow Planck's equation. On the other hand, the heat radiation from the object to be heated, which is an actual object, is smaller than the heat radiation from the black body, and the emissivity (ratio to the heat radiation from the black body) depends on the material of the object to be heated 2 as the measurement object. ) Is different. Therefore, by detecting the thermal radiation at each of the two wavelengths by the two light receiving elements, the influence due to the difference in the emissivity of the object to be heated is reduced to improve the accuracy of temperature measurement.

In the case where InGaAs photodiodes of type G ₁ and G ₂ are used as the two light receiving elements, the heat radiation from the object to be heated 2 that is the measurement object is compared in the wavelength range in which these InGaAs photodiodes are sensitive. Therefore, the temperature of the object to be heated 2 can be detected with high sensitivity. However, a temperature detection device using an InGaAs photodiode can detect thermal radiation with high sensitivity, but is expensive.

Compared with this, when the Si photodiodes of types S ₁ and S ₂ are used as the Si photodiodes 141 and 142, the object to be measured is near the wavelength at which the sensitivity of these Si photodiodes peaks. The heat radiation from a certain heated object 2 is extremely small, and it is extremely difficult to detect the temperature of the heated object 2. Therefore, when a Si photodiode is used, there is a certain amount of heat radiation from the object to be heated 2 at a wavelength longer than this peak wavelength, not near the wavelength at which the light receiving sensitivity of the Si photodiode reaches a peak. detecting the thermal radiation with the light receiving sensitivity wavelength (around 1.1μm from the vicinity of the peak wavelength 840nm type _{S 2).}

  However, in general, the spectral sensitivity characteristics of the Si photodiode have a large variation between individuals and a large temperature dependency. FIG. 7 is a graph showing an example of the wavelength dependence of the temperature coefficient of the spectral sensitivity characteristic of the Si photodiode. As shown in this figure, the temperature dependence of the spectral sensitivity characteristic of the Si photodiode is large in the vicinity of the wavelength of the thermal radiation to be detected.

Therefore, in the present embodiment, as described above, each of the first signal processing circuit 151 and the second signal processing circuit 152 includes sensitivity adjustment means for adjusting the relationship of the output voltage value with respect to the input current value. The sensitivity adjusting means includes means for adjusting the amplification factor of each amplifier circuit (resistor R ₃₃ having a variable resistance value). Further, each of the first signal processing circuit 151 and the second signal processing circuit 152 includes a temperature correction unit that corrects a change in spectral sensitivity characteristic due to a temperature change of the corresponding Si photodiode. the resistor R ₃₁ whose resistance value changes with temperature as the temperature compensation means includes amplifier circuit.

  Thus, since the temperature detection apparatus 10 according to the present embodiment is a non-contact type using a Si photodiode, the temperature detection responsiveness is excellent and inexpensive. Even if there is a large variation in temperature detection between individual Si photodiodes, the temperature detection device 10 can detect temperature by the first signal processing circuit 151 and the second signal processing circuit 152 including sensitivity adjustment means. Improves accuracy. Furthermore, even if the temperature dependence of the spectral sensitivity characteristic of the Si photodiode is large, the temperature detection device 10 has this feature because each of the first signal processing circuit 151 and the second signal processing circuit 152 includes temperature correction means. However, the accuracy of temperature detection is improved.

It is principal part sectional drawing of the cooking heater apparatus 1 provided with the temperature detection apparatus 10 which concerns on this embodiment. It is sectional drawing of the temperature detection element 11 of the temperature detection apparatus 10 which concerns on this embodiment. It is a block diagram of the signal processing part 150 of the temperature detection apparatus 10 which concerns on this embodiment. 3 is a circuit diagram of a first signal processing circuit 151 of the temperature detection device 10 according to the present embodiment. FIG. It is a figure which shows the example of the cross section of the 1st Si photodiode 141 and the 2nd Si photodiode 142 of the temperature detection apparatus 10 which concerns on this embodiment. It is a figure which shows the black body radiation | emission characteristic, the sensitivity characteristic of Si photodiode, and the sensitivity characteristic of an InGaAs photodiode. It is a graph which shows an example of the wavelength dependence of the temperature coefficient of the spectral sensitivity characteristic of Si photodiode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Cooking heater apparatus, 2 ... Heated object, 10 ... Temperature detection apparatus, 11 ... Temperature detection element, 12 ... Operation part, 20 ... Top plate, 21 ... Window part, 30 ... Magnetic field generation coil, 40 ... Power supply circuit, 110 DESCRIPTION OF SYMBOLS ... Housing | casing 120 ... Board | substrate 131 ... 1st optical system, 132 ... 2nd optical system, 141 ... 1st Si photodiode, 142 ... 2nd Si photodiode, 150 ... Signal processing part, 151 ... 1st signal processing circuit, 152: second signal processing circuit, 161: current-voltage conversion circuit, 162: low-pass filter, 163: amplifier circuit, 164: low-pass filter

Claims (7)

A temperature detection device that detects the temperature of the measurement object based on thermal radiation radiated from the measurement object,
A first Si photodiode having a first spectral sensitivity characteristic and outputting a current signal having a value corresponding to the incident amount of the thermal radiation based on the first spectral sensitivity characteristic;
A second Si photodiode having a second spectral sensitivity characteristic different from the first spectral sensitivity characteristic and outputting a current signal having a value corresponding to the incident amount of the thermal radiation based on the second spectral sensitivity characteristic;
A first signal processing circuit for inputting a current signal output from the first Si photodiode and outputting a voltage signal having a value corresponding to the value of the current signal;
A second signal processing circuit for inputting a current signal output from the second Si photodiode and outputting a voltage signal having a value corresponding to the value of the current signal;
With
The first signal processing circuit includes first sensitivity adjusting means for adjusting a relationship of an output voltage value to an input current value;
The second signal processing circuit includes a second sensitivity adjusting means for adjusting a relationship of an output voltage value to an input current value;
A temperature detecting device characterized by that.   2. The temperature detection according to claim 1, further comprising a calculation unit that calculates a temperature of the measurement object based on a value of a voltage signal output from each of the first signal processing circuit and the second signal processing circuit. apparatus. A first current-voltage conversion circuit for converting the input current signal into a voltage signal; and a first amplification for amplifying and outputting the voltage signal output from the first current-voltage conversion circuit. A circuit, and means for adjusting an amplification factor of the first amplifier circuit as the first sensitivity adjusting means,
A second current-voltage conversion circuit for converting the input current signal into a voltage signal; and a second amplification for amplifying and outputting the voltage signal output from the second current-voltage conversion circuit. A circuit and means for adjusting an amplification factor of the second amplifier circuit as the second sensitivity adjustment means,
The temperature detection device according to claim 1. The first Si photodiode and the second Si photodiode have different light detection regions;
A first optical system for guiding thermal radiation radiated from a certain range of the surface of the measurement object to the first Si photodiode, and a second optical system for guiding thermal radiation radiated from the certain range to the second Si photodiode And further comprising
The temperature detection device according to claim 1.   2. The temperature detecting device according to claim 1, wherein the first Si photodiode and the second Si photodiode are formed on a common Si substrate. The first Si photodiode and the second Si photodiode have a light detection region where they overlap each other,
An optical system for guiding thermal radiation radiated from a predetermined range of the surface of the measurement object to the first Si photodiode and the second Si photodiode;
The temperature detection apparatus according to claim 5, wherein 2. The temperature detection device according to claim 1, wherein the first Si photodiode and the second Si photodiode are arranged on a common circuit board.

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