JPH1019816A - Temperature regulator for sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sustain the sensor temperature at a constant level by providing a plurality of impedance means, a sensor, a voltage generating means, a voltage comparing means, a heater drive means, etc. SOLUTION: Point A between a first impedance means, i.e., a first resistor 8, and a CO sensor 1 and point B between a second impedance means, i.e., a second resistor 9, and a third impedance means, i.e., a third resistor 10 are connected to respective input terminals of a voltage comparing means 5 through AC-DC conversion means 11, 12, respectively, in order to drive a heater 7. When the temperature of the CO sensor 1 is constant and the output voltage from an AC voltage generating means 3 is varied, voltage at the point A is varied but since voltage at the point B is also varied, the variations are canceled. Consequently, the effect of fluctuation in the output voltage from the AC voltage generating means 3 is substantially eliminated and the sensor temperature can be kept at a constant level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature control device for a sensor whose heating is controlled by a heater or the like.

[0002]

2. Description of the Related Art As a sensor controlled by a heater, there is a sensor using stabilized zirconia, which is widely used as a CO sensor because of its characteristics such as little deterioration. References include Japanese Patent Application Laid-Open No. 57-22101.
No. 9 publication. By the way, such a CO sensor using stabilized zirconia obtains stable gas sensitivity.
It is necessary to keep the temperature at about 400 ° C. FIG. 4 is a graph showing a change in impedance with respect to the temperature of the stabilized zirconia element, and FIG. 5 is a schematic diagram of a conventional temperature control device for a sensor. In order to keep the temperature of a CO sensor at 400 ° C., FIG. By utilizing the fact that the impedance of the stabilized zirconia element decreases as the temperature increases, as shown in FIG. 5, a voltage is applied from a voltage generating means 3 to a circuit in which a CO sensor 1 and a resistor 2 are connected in series. , CO
The divided voltage generated by the sensor 1 and the resistor 2 is compared with a reference voltage from a reference voltage source 4 using a voltage comparison unit 5, and an output voltage corresponding to a difference between the two is supplied to a heater driving unit 6. There has been a sensor temperature control device that keeps the sensor temperature constant by driving.

The change in the impedance shown in FIG. 4 is obtained by connecting the output / temperature AC signal input / output line of the CO sensor to an impedance analyzer (manufactured by Hewlett-Packard Japan Co., Ltd.) and controlling the temperature of the CO sensor by the heater of the CO sensor. While changing the values, values at 10 ° C. were obtained from 330 to 470 ° C., respectively. The temperature of the CO sensor was measured with a K-type thermocouple embedded in the catalyst of the CO sensor.

However, in the prior art shown in FIG. 5, when the output voltage of the voltage generating means 3 changes for some reason such as a change in air temperature, the above-mentioned divided voltage also changes even though the sensor temperature is constant. As a result, there is a problem that an incorrect sensor temperature is detected.

[0005]

The first, second and third aspects of the present invention provide a temperature control device for a sensor for maintaining a constant sensor temperature. The invention described in claim 4 provides, in addition to the invention described in claim 2 or 3, a low-cost, low-temperature sensor temperature controller. The invention described in claim 5 is the same as the invention described in claim 2 or 3,
In particular, it is an object of the present invention to provide a temperature adjusting device for a sensor which maintains the temperature of the sensor constant with high accuracy. The invention according to claim 6 is
In addition to the invention described in the first, second, third, fourth, or fifth aspect, the present invention provides a temperature adjusting device for a sensor having a long life.

[0006]

According to the present invention, there is provided a temperature control apparatus for a sensor which is controlled to be heated by a heater, comprising: a first impedance means, a second impedance means, a third impedance means, a sensor, a voltage generation means, and a voltage control means. The present invention relates to a temperature adjusting device for a sensor including a comparing unit and a heater driving unit. Further, the present invention provides the above-mentioned temperature control device for a sensor, wherein the first impedance means and the sensor are connected in series, the second impedance means and the third impedance means are connected in series, and both ends of these are connected. Each is connected between the output terminals of the AC voltage generating means,
Further, the present invention relates to a temperature control device for a sensor, which is connected between the first impedance means and the sensor and between the second impedance means and the third impedance means to each input terminal of the voltage comparison means via the AC-DC conversion means. .

Further, the present invention provides the above-mentioned temperature control device for a sensor, wherein the first impedance means and the sensor are connected in series, and the first AC-DC conversion means, the second impedance means and the third impedance means are connected to each other. Impedance means are connected in series, both ends thereof are respectively connected between output terminals of the AC voltage generation means, and a portion passing between the first impedance means and the sensor through the second AC-DC conversion means and a second part. The present invention relates to a temperature control device for a sensor connected between the impedance means and the third impedance means and to each input terminal of the voltage comparison means.

The present invention also relates to a temperature control apparatus for a sensor, wherein the AC-DC conversion means performs conversion using a diode for performing half-wave rectification and a capacitor for maintaining a peak value. . In addition, the present invention relates to a temperature control device for a sensor in which the AC-DC conversion means performs conversion using a transistor that performs half-wave rectification and a capacitor that maintains a peak value in the above-described temperature control device for a sensor. Further, the present invention relates to the temperature adjusting device for a sensor, wherein the sensor is a CO sensor using stabilized zirconia.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the first, second and third impedance means include, for example, a resistor and a capacitor. Examples of the voltage generating means include a DC power supply and a sine wave transmitter. As the voltage comparison means, for example, there is a device that outputs a DC voltage proportional to a difference between voltages applied between input terminals. Further, as the heater driving unit, for example, there is a device that supplies a driving current according to the output voltage of the voltage comparing unit to the heater.

When the temperature controller of the present invention has a plurality of AC-DC converters, it is preferable that all of them are converted by the same method. For example, if a diode that performs half-wave rectification and a capacitor that holds the peak value are used, conversion is performed using this method.If a transistor that performs half-wave rectification and a capacitor that performs peak value holding are used, conversion is performed using this method. This is preferable because the difference in temperature variation of the sensor is smaller than when the conversion is performed by combining the different methods.

Next, an operation method of the temperature control device for the sensor will be described with reference to FIGS. FIG. 1 is a circuit block diagram of a temperature control device for a sensor according to the present invention, in which a first impedance means [resistance (R1)] and a CO sensor 1 using stabilized zirconia are connected in series, and The impedance means [resistance (R2)] and the third impedance means [resistance (R3)] are connected in series, both ends of which are connected between the output terminals of the AC voltage generation means 3, respectively. (R1) and the point A between the CO sensor 1 and the second impedance means (R
A point B between 2) and the third impedance means (R3) is respectively connected to each input terminal of the differential amplifier as the voltage comparison means 5 and a diode (D2) of the AC-DC conversion means.
And the capacitor (C2) and the diode (D1) via the capacitor (C1). Further, as a heater driving means, a driving current corresponding to an output voltage from the voltage comparing means 5 and a current from the DC power supply (E) are adjusted by the transistor (Q1) and supplied to the heater 7.

The temperature control device for a sensor according to the present invention is configured as described above, and converts the voltages at points A and B in FIG. 1 from an AC voltage to a DC voltage using the above-described AC-DC converter. As a result, a general differential amplifier can be used as the voltage comparison means 5. At this time, as described above, the same method is used for each of the AC-DC converters used, and the AC-DC converter is connected to each input terminal of the differential amplifier, which is the voltage comparator 5, by the AC-DC converter. The difference between the generated output voltage changes is canceled out, and the influence on the heater 7 can be made very small, so that the sensor temperature can be kept constant.

FIG. 2 is a circuit block diagram of another temperature control device for a sensor according to the present invention, in which a first impedance means [resistance (R1)] and a CO sensor 1 using stabilized zirconia are connected in series. Also, a portion of the first AC-DC converter through the transistor (Q1) and the resistor (R4) and the capacitor (C1), the second impedance means [the resistor (R2)] and the third impedance means [the resistor ( R
3)] are connected in series, both ends of which are connected between the output terminals of the AC voltage generating means 3, respectively, and further from the extension of the point A between the first impedance means (R 1) and the CO sensor 1. As the second AC-DC conversion means, a portion via the transistor (Q2) and the resistor (R5) and the capacitor (C2) and a portion between the second impedance means (R2) and the third impedance means (R3) are provided. Point B is connected to each input terminal of a differential amplifier as voltage comparison means 5. In the same manner as above, as a heater driving means, a driving current corresponding to the output voltage from the voltage comparing means 5 and a current from the DC power supply (E) are adjusted by the transistor (Q3) and supplied to the heater 7.

Another sensor temperature control device of the present invention is configured as described above, and operates in the same manner as in the first embodiment.
The sensor temperature can be kept constant.

FIG. 3 shows an example of a schematic diagram of a temperature control device for a sensor according to the present invention. In the present invention, a first resistor 8 as first impedance means and a CO sensor 1 are connected in series. A second resistor 9 as a second impedance means and a third resistor 10 as a third impedance means are connected in series, and both ends thereof are connected between output terminals of the AC voltage generating means 3 respectively. And the first resistor 8
The point A between the first and second resistors 9 and 10 and the point B between the second resistor 9 and the third resistor 10 are connected to the respective input terminals of the voltage comparator 5 via the AC-DC converters 11 and 12, respectively. The output of the voltage comparison means 5 is connected to the heater driving means 6
, And drives the heater 7. With such a configuration, when the temperature of the CO sensor 1 is constant and the output voltage of the AC voltage generating means 3 changes, the voltage at the point A changes. Similarly, the voltage at the point B also changes. The two are canceled and the output of the voltage comparison means 5 has almost no effect on the change of the output voltage from the AC voltage generation means 3, so that the sensor temperature can be kept constant.

[0016]

Examples of the present invention will be described below, but the present invention is not limited to these examples. C used in Examples
The O sensor is composed of 8 mol% of yttria as a stabilizer with respect to 92 mol% of zirconia in the longitudinal direction in the ceramic cylinder.
The interior of the ceramic cylinder is divided into two chambers, one of which is filled with a platinum-alumina catalyst, the other is filled with a tin oxide catalyst, and both ends of the ceramic cylinder are made of porous ceramic. It is sealed with a plate, and the output / temperature AC signal input / output line of the CO sensor is pulled out from the hole of the porous ceramic plate to the outside from a pair of electrodes provided on both sides of the zirconia element. What wound a nichrome wire was used.

In the embodiment of the present invention, the above-mentioned CO sensor is incorporated in the circuits shown in the block diagrams of FIGS. 1 and 2 and used as a temperature control device for the sensor. Further, in the embodiment of the present invention, the DC-AC
In FIG. 2, replacement was performed using a diode that performs half-wave rectification and a capacitor that performs peak value holding, while in FIG. 2, replacement was performed using a transistor that performs half-wave rectification and a capacitor that performs peak value holding.

In the embodiment, the CO sensor is a cylindrical C
Although an example using an O sensor has been described, a flat plate type CO sensor can also be used in the present invention.

[0019]

According to the temperature adjusting device for a sensor according to the first, second and third aspects, the sensor temperature can be kept constant. The temperature control device for a sensor according to the fourth aspect is the second or third aspect.
The effect of the temperature control device for the sensor described above is exhibited, and the number of components can be reduced and the sensor can be manufactured at low cost. The temperature adjusting device for a sensor according to the fifth aspect has the effect of the temperature adjusting device for the sensor according to the second or third aspect, and can keep the sensor temperature constant with high accuracy. The temperature adjusting device for a sensor according to the sixth aspect has the effect of the temperature adjusting device for the sensor according to the first, second, third, fourth or fifth aspect, and is a temperature adjusting device for a sensor having a longer life.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of a temperature control device for a sensor according to an embodiment of the present invention.

FIG. 2 is a circuit block diagram of a temperature control device for a sensor according to another embodiment of the present invention.

FIG. 3 is an example of a schematic view of a temperature control device for a sensor according to the present invention.

FIG. 4 is a graph showing a change in impedance with respect to temperature of a stabilized zirconia element.

FIG. 5 is a schematic view of a conventional temperature control device for a sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CO sensor 2 Resistance 3 Voltage generation means 4 Reference voltage source 5 Voltage comparison means 6 Heater driving means 7 Heater 8 First resistance 9 Second resistance 10 Third resistance

Claims (6)

[Claims] 1. A temperature control device for a sensor which controls heating by a heater, comprising: a first impedance unit, a second impedance unit, a third impedance unit, a sensor, a voltage generation unit, a voltage comparison unit, and a heater driving unit. A temperature control device for the configured sensor. 2. A first impedance means and a sensor are connected in series, a second impedance means and a third impedance means are connected in series, and both ends thereof are respectively connected between output terminals of the AC voltage generation means. 2. The input terminal of the voltage comparison means connected between the first impedance means and the sensor and between the second impedance means and the third impedance means via the AC-DC conversion means. Sensor temperature control device. 3. A first impedance means and a sensor are connected in series, a first AC-DC conversion means, a second impedance means and a third impedance are connected in series, and both ends of the first and second impedance means are connected to each other. A portion connected between the output terminals of the voltage generating means, a portion through the second AC-DC converting means from between the first impedance means and the sensor, and a voltage comparing means from between the second impedance means and the third impedance means. The temperature control device for a sensor according to claim 1, wherein the temperature control device is connected to each input terminal. 4. The temperature control device for a sensor according to claim 2, wherein the AC-DC conversion means performs conversion using a diode performing half-wave rectification and a capacitor performing peak value holding. 5. The temperature control device for a sensor according to claim 2, wherein the AC / DC converter converts the voltage using a transistor that performs half-wave rectification and a capacitor that maintains a peak value. 6. A CO sensor using stabilized zirconia as a sensor.
The sensor temperature control device according to claim 1, 2, 3, 4, or 5, which is a sensor.