JP2017194392A - Temperature detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a temperature detection device that has reduced a difference in detected temperature caused by a change in power supply voltage.SOLUTION: A sensor module 1 comprises: a thermopile part 11; a reference voltage circuit 13 that generates a reference voltage from an input power supply voltage and applies the reference voltage to the thermopile part 11; and an output terminal VrefOut that outputs the reference voltage. An A/D converter 2 includes an input terminal Vin1 to which an output voltage from the thermopile part 11 is applied and an input terminal VrefIn that is connected to the output terminal VrefOut of the sensor module 11, and performs A/D conversion of the output voltage from the thermopile part 11 applied to the input terminal Vin1 with a voltage applied to the input terminal VrefIn as a reference voltage Vref0 for the A/D conversion.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a temperature detection device.

  When detecting the temperature of a specific part of an electronic device, a thermistor or a thermopile is used. For example, in an electrophotographic image forming apparatus, a non-contact type temperature sensor that detects the temperature of the heat roller by detecting the amount of infrared rays from the heat roller of the fixing device with a thermopile may be used (for example, Patent Document 1). reference).

  Some sensor modules of such non-contact type temperature sensors have a thermopile in which thermocouples are connected in series, and a thermistor for measuring the cold spot temperature (reference temperature) of the thermopile. The sensor module outputs the output voltage of the thermopile (that is, temperature difference information) and the output voltage of the temperature detection circuit by the thermistor (that is, reference temperature information).

  FIG. 3 is a block diagram illustrating an example of the temperature detection device. In the temperature detection device shown in FIG. 3, the sensor module 101 includes a thermopile unit 111, a thermistor unit 112, a reference voltage circuit 113, and a nonvolatile memory 114. The reference voltage circuit 113 generates a constant reference voltage Vref1 from the input power supply voltage Vcc and applies it as a power supply voltage to internal circuits such as the thermopile unit 111 and the thermistor unit 112. The nonvolatile memory 114 stores characteristic data 121 that is unique to the sensor module 101 and indicates the relationship between the output voltage of the sensor module 101 and the detected temperature. FIG. 4 is a diagram illustrating an example of the relationship between the output voltage indicated by the characteristic data 121 stored in the sensor module 101 and the temperature difference of the thermopile unit 111.

  The A / D (Analog to Digital) converter 102 uses the input power supply voltage Vcc as a reference voltage, and outputs the output voltage Vout1 from the thermopile unit 111 of the sensor module 101 and the output voltage Vout2 from the thermistor unit 112 of the sensor module 101. A / D conversion is performed, and digital data Data 1 and Data 2 obtained by the A / D conversion are output to the control circuit 103. The control circuit 103 reads the characteristic data 121 and identifies the detected temperature from the digital data Data 1 and Data 2 based on the characteristic data 121.

JP 2007-173218 A

  However, in the apparatus shown in FIG. 3, when the input power supply voltage Vcc of the sensor module 101 and the A / D converter 102 fluctuates, the power supply voltages of the thermopile unit 111 and the thermistor unit 112 are constant at the reference voltage Vref1. Therefore, the A / D converter 102 uses the input power supply voltage Vcc as the reference voltage Vref0 for A / D conversion, but the output value of the sensor module 101 varies. Even if not, the values of the output digital data Data1 and Data2 will fluctuate due to fluctuations in the input power supply voltage Vcc.

  That is, when there is no change in the A / D conversion reference voltage Vref0, the value of Data1 is expressed by the following equation.

Data1 = n × Vout1 / Vref0

  However, n is the maximum value (constant) of A / D conversion.

  On the other hand, when Vref0 fluctuates p times, the value of Data1 (Data1_error) is expressed by the following equation.

Data1_error = n × Vout1 / (Vref0 × p) = Data1 × (1 / p)

  FIG. 5 is a diagram for explaining an error in temperature control caused by fluctuations in the input power supply voltage Vcc. FIG. 5 shows a case where the normal reference voltage is 3.3 volts and the reference voltage is reduced by 5% to 3.135 volts (p = 0.95). As described above, the sensor module 101 is not affected by fluctuations in the input power supply voltage Vcc, but the A / D converter 102 is affected by fluctuations in the input power supply voltage Vcc. When the temperature of the temperature control target (for example, the heat roller of the fixing device) is set to 230 degrees Celsius, the A / D of Vout1 derived from the characteristic data 121 of the sensor module 101 in consideration of the cold spot temperature based on Data2. Since the conversion value (digital data value) is 651, the temperature of the temperature control target is adjusted so that the A / D conversion value becomes 651. However, when the reference voltage Vref0 of the A / D converter 102 is fluctuating, adjusting the temperature of the temperature control target so that the A / D conversion value becomes 651, as shown in FIG. The temperature is adjusted to 215.5 degrees Celsius.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to obtain a temperature detection device with a small detection temperature error due to fluctuations in power supply voltage.

  The temperature detection device according to the present invention includes a sensor module and an A / D converter. The sensor module includes a thermopile unit, a reference voltage circuit that generates a reference voltage from an input power supply voltage and applies the reference voltage to the thermopile unit, and an output terminal that outputs the reference voltage. The A / D converter includes a first input terminal to which an output voltage of the thermopile unit is applied and a second input terminal connected to the output terminal of the sensor module, and is applied to the second input terminal. Using the voltage as a reference voltage for A / D conversion, the output voltage of the thermopile unit applied to the first input terminal is A / D converted.

  According to the present invention, it is possible to obtain a temperature detection device with a small detection temperature error caused by fluctuations in power supply voltage.

  These and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

FIG. 1 is a block diagram showing a configuration of a temperature detection device according to an embodiment of the present invention. FIG. 2 is a diagram illustrating an example of the relationship between the ratio between the reference voltage and the output voltage indicated by the characteristic data 21 stored in the sensor module 1 in FIG. 1 and the temperature difference of the thermopile unit 11. FIG. 3 is a block diagram illustrating an example of the temperature detection device. FIG. 4 is a diagram illustrating an example of the relationship between the output voltage indicated by the characteristic data 121 stored in the sensor module 101 in FIG. 3 and the temperature difference of the thermopile unit 111. FIG. 5 is a diagram for explaining an error in temperature control caused by fluctuations in the input power supply voltage Vcc.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a temperature detection device according to an embodiment of the present invention. In this embodiment, the temperature detection device is built in an image forming device (printer, multifunction device, etc.) in order to detect the temperature of the heat roller of the fixing device (that is, the fixing temperature). However, a similar temperature detection device can be incorporated in other types of electronic devices.

  The temperature detection apparatus shown in FIG. 1 includes a sensor module 1, an A / D converter 2, and a control circuit 3.

  The sensor module 1 includes a thermopile unit 11, a thermistor unit 12, a reference voltage circuit 13, a non-volatile memory 14, an output terminal VrefOut that outputs a reference voltage Vref 1 by the reference voltage circuit 13, and an output of the thermopile unit 11. An output terminal Vout1 that outputs a voltage, an output terminal Vout2 that outputs an output voltage of the thermistor section 12, a data output terminal Data for reading data from the memory 14 from the outside, and an input terminal to which an input power supply voltage Vcc is applied VccIn.

  The reference voltage circuit 13 generates a reference voltage Vref1 from the thermistor unit 12 and the input power supply voltage Vcc and applies it to the thermopile unit 11, the thermistor unit 12, and the like.

  Since the characteristics of the thermopile unit 11 are different for each sensor module 1, the memory 14 stores characteristic data 21 unique to the sensor module 1. The characteristic data 21 indicates the relationship between the ratio between the reference voltage Vref1 by the reference voltage circuit 13 and the output voltage of the thermopile unit 11 and the detected temperature. FIG. 2 is a diagram illustrating an example of the relationship between the ratio between the reference voltage and the output voltage indicated by the characteristic data 21 stored in the sensor module 1 in FIG. 1 and the temperature difference of the thermopile unit 11.

  For example, the characteristic data 21 is a parameter (coefficient) of a specific approximate function. For example, the characteristic data 21 is a coefficient of each order in an approximate function using a polynomial of a predetermined order.

  The A / D converter 2 performs A / D conversion on the output voltage of the sensor module 1 and outputs digital data obtained by the A / D conversion.

  The A / D converter 2 has an input terminal Vin1 to which the output voltage of the thermopile unit 11 is applied, an input terminal Vin2 to which the output voltage of the thermistor unit 12 is applied, and an input connected to the output terminal VrefOut of the sensor module. And a terminal VrefIn.

  Then, the A / D converter 2 uses the voltage applied to the input terminal VrefIn as a reference voltage for A / D conversion, and A / D converts the output voltage of the thermopile unit 11 applied to the input terminal Vin1 to digital data Data1. At the same time, the output voltage of the thermistor section 12 applied to the input terminal Vin2 is A / D converted into digital data Data2. The A / D converter 2 outputs digital data Data1 and Data2 from the data output terminal DataOut. The digital data Data1 and Data2 may be output serially or in parallel.

  The control circuit 3 includes a computer including an application specific integrated circuit (ASIC) and a processor (for example, a central processing unit (CPU)), and performs various processes. The control circuit 3 applies the input power supply voltage Vcc to the sensor module 1 and the A / D converter 2, and outputs the output voltage of the thermopile unit 11 and the output voltage of the thermistor unit 12 from the A / D converter 2 to the A / D. The digital data Data1 and Data2 obtained by the conversion are acquired, the characteristic data 21 is read from the memory 14 via the data output terminal Data, and the detected temperature is specified from the acquired digital data Data1 and Data2 based on the characteristic data 21 .

  Here, since the characteristic data 21 indicates a temperature difference corresponding to the ratio of the output value Vout1 to the reference voltage Vref1, the detected temperature is specified without considering the value of the input power supply voltage Vcc that may vary. .

  That is, the reference temperature of the thermistor unit 12 is specified from Data2 based on the characteristics of the thermistor unit 12, and the ratio between Data1 and the maximum value of the digital data and the characteristic data 21 (the function based on the characteristic data 21 with respect to the ratio). Since the temperature difference of the thermopile unit 11 can be specified (by obtaining the value of the relational expression), the detected temperature is specified from the characteristic data 21 and the digital data Data1 and Data2.

  In this embodiment, the control circuit 3 controls the energization to the heat roller based on the detected temperature, thereby adjusting the fixing temperature of the fixing device that fixes the toner on the printing paper by the heat and pressure method. Control.

  Next, the operation of the temperature detection device will be described.

  The sensor module 1 outputs the reference voltage Vref1 from the built-in reference voltage circuit 13 to the A / D converter 2 together with the output voltage of the thermopile unit 11 and the output voltage of the thermistor unit 12.

  The A / D converter 2 uses the reference voltage Vref1 as the A / D conversion reference voltage Vref0, and A / D converts the output voltage of the thermopile unit 11 and the output voltage of the thermistor unit 12 into digital data Data1 and Data2, Digital data Data 1 and Data 2 are output to the control circuit 3.

  The control circuit 3 reads the characteristic data 21 from the memory 14 of the module 1 and specifies the detected temperature from the digital data Data1 and Data2 based on the characteristic data 21. And the control circuit 3 controls the temperature of temperature control object based on the specified detected temperature.

  As described above, according to the embodiment, the sensor module 1 generates the reference voltage from the thermopile unit 11, the thermistor unit 12, and the input power supply voltage, and applies the reference voltage to the thermopile unit 11 and the thermistor unit 12. A voltage circuit 13 and an output terminal VrefOut for outputting the reference voltage are provided. The A / D converter 2 includes an input terminal Vin1 to which the output voltage of the thermopile unit 11 is applied, and an input terminal VrefIn connected to the output terminal VrefOut of the sensor module 11, and the voltage applied to the input terminal VrefIn is As the reference voltage Vref0 for A / D conversion, the output voltage of the thermopile unit 11 applied to the input terminal Vin1 is A / D converted.

  Thereby, even if the power supply voltage Vcc varies, the A / D converter 2 performs A / D conversion based on the constant reference voltage Vref1 common to the thermopile unit 11 and the thermistor unit 12 of the sensor module 1. The value of the digital data after A / D conversion is not affected by the fluctuation of the power supply voltage Vcc, and the detection temperature error caused by the fluctuation of the power supply voltage Vcc is reduced.

  Various changes and modifications to the above-described embodiment will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the subject matter and without diminishing its intended advantages. That is, such changes and modifications are intended to be included within the scope of the claims.

  The present invention is applicable to, for example, fixing temperature control.

DESCRIPTION OF SYMBOLS 1 Sensor module 2 A / D converter 3 Control circuit 11 Thermopile part 12 Thermistor part 13 Reference voltage circuit 14 Memory 21 Characteristic data

Claims (6)

A sensor module;
An A / D converter,
The sensor module includes a thermopile unit, a reference voltage circuit that generates a reference voltage from an input power supply voltage and applies the reference voltage to the thermopile unit, and an output terminal that outputs the reference voltage,
The A / D converter includes a first input terminal to which an output voltage of the thermopile unit is applied and a second input terminal connected to the output terminal of the sensor module, and is applied to the second input terminal. A / D conversion is performed on the output voltage of the thermopile unit applied to the first input terminal using a voltage as a reference voltage for A / D conversion;
A temperature detection device characterized by. The sensor module further includes a nonvolatile memory and a data output terminal for reading data in the memory from the outside,
The memory stores characteristic data indicating a relationship between a ratio between the reference voltage by the reference voltage circuit and an output voltage of the thermopile unit and a detected temperature;
The temperature detection device according to claim 1.   The digital data obtained by A / D converting the output voltage of the thermopile unit is acquired from the A / D converter, the characteristic data is read from the memory, and the acquired digital data is obtained based on the characteristic data. The temperature detection apparatus according to claim 2, further comprising a control circuit that specifies the detected temperature from the control circuit.   The temperature detection device according to claim 3, wherein the control circuit controls a fixing temperature of the fixing device based on the detected temperature. A control circuit,
The sensor module further includes a thermistor portion,
The reference voltage circuit applies the reference voltage to the thermopile part and the thermistor part,
The A / D converter further includes a third input terminal to which the output voltage of the thermistor unit is applied, and A / D converts the output voltage of the thermistor unit to be applied to the third input terminal,
The control circuit acquires digital data obtained by A / D converting the output voltage of the thermopile unit and the output voltage of the thermistor unit from the A / D converter, and reads the characteristic data from the memory Identifying the detected temperature from the acquired digital data based on the characteristic data;
The temperature detection device according to claim 2. The sensor module further includes a thermistor portion,
The reference voltage circuit applies the reference voltage to the thermopile part and the thermistor part,
The A / D converter further includes a third input terminal to which the output voltage of the thermistor section is applied, and A / D converts the output voltage of the thermistor section applied to the third input terminal. ,
The temperature detection device according to claim 1.

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