JPH04309826A - Temperature detector - Google Patents

Abstract

PURPOSE:To provide a temperature detecting sensor circuit having excellent detecting accuracy and hardly producing difference in temperature detecting accuracy by temperature areas by detecting temperatures in different temperature areas by means of a thermosensitive resistance element. CONSTITUTION:A thermosensitive resistance element T1 and resistors R1 and R2 are connected in series to each other, and partial pressure voltage, which is generated by the thermosensitive element T1 capable of changing by temperatures and the resistors R1 and R2, is obtained, and this is inputted to a control circuit C1 provided with at least two sets of temperature related scales corresponding to the partial pressure voltage, on the one hand, and when switching signals from signal input means R3 and R5 are inputted to the control circuit C1, the related scales are switched, and the control circuit C1 also outputs switching output signals, and operates a switching means S1, and switches resistance values of the resistors connected in series to the thermosensitive resistance element T1. By means of this operation, the thermosensitive resistance element T1 can detect accurately dispersion of temperature detecting accuracy, which is caused by reason that resistance value change generated by temperatures is not constant by temperature areas, in every temperature detecting area.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a temperature detection device.
More specifically, the present invention relates to a temperature detection device that can accurately detect temperatures in at least two temperature ranges using one heat-sensitive resistance element.

0002

[Prior Art] For example, temperature control in combustion equipment such as oil fan heaters involves not only control during normal combustion that is always executed, but also incineration (incineration) of high-boiling coal that accumulates in the combustor.
control for cleaning) is executed at any time. To process high-boiling point coal, it is incinerated at a higher temperature than normal combustion, so combustor temperature control is required in two temperature ranges. As a temperature sensor for this temperature control, a heat-sensitive resistance element such as a thermistor is usually attached to the vaporizer. When detecting temperature with this thermistor, it is easy to detect one temperature range, but in order to detect greatly different temperature ranges such as normal combustion and cleaning with one thermistor, it is necessary to change the temperature at which the detection temperature range is switched. Requires detection sensor circuit. Figure 3 shows a conventional temperature detection device. This temperature detection device is capable of detecting temperatures in two temperature ranges using a thermistor T, and a control circuit C stores in a memory M1 only one column of a relation scale SC between temperature and a partial voltage that changes depending on the temperature. In Fig. 3, to detect the temperature during normal combustion, a resistor Ra is connected in series with the thermistor T, and the resistance value of the resistor Ra is adjusted according to the characteristic value of the thermistor T so that the control temperature during normal combustion can be detected. Select, thermistor T and resistor Ra
The divided voltage caused by the voltage is input to the control circuit C through the protective resistor Rc, and the resistance change due to temperature of the thermistor T is read as a voltage change, and the temperature is specified using the relational scale SC. On the other hand, for temperature detection during cleaning, switch S is closed and thermistor T and resistor Ra
By connecting a resistor Rb in parallel with and shifting the detection temperature setting of the thermistor T to the cleaning temperature range, input the divided voltage between the thermistor T and the resistor Ra to the control circuit C, and use the above-mentioned relational scale SC. The temperature at that time is determined.

0003

[Problem to be Solved by the Invention] When detecting two different set temperatures in the temperature detection device shown in the conventional example above, one of the two detection temperature ranges is detected by the resistance temperature characteristic of the thermistor T. There was a problem in that if one was set to a point with good detection accuracy, the other had to be set to a point with poor detection accuracy. In the case of the above-mentioned combustion equipment, priority is given to temperature detection during normal combustion, and this temperature is, for example, 250°C to 300°C.
If priority is given to detecting the set temperature in the temperature range of .degree. C., the accuracy of detecting the set temperature in the temperature range of, for example, 400.degree. C. to 450.degree. C. during cleaning becomes poor. This is due to the fact that the resistance-temperature characteristics of heat-sensitive resistance elements such as thermistors are not constant over a wide temperature range.
For example, as shown in FIG. 4, the resistance temperature characteristic of a negative characteristic thermistor is such that the rate of change in resistance value due to temperature becomes small near the upper and lower limits (C and b). Therefore, even when reading a change in resistance value due to temperature as a change in voltage, the reading accuracy deteriorates in a temperature range close to the upper limit value and the lower limit value. In the case of the above-mentioned combustion equipment, temperature detection during normal combustion is controlled by setting it in temperature range a with good detection accuracy in Figure 4, so temperature detection during cleaning is set in temperature range b with poor detection accuracy. As a result, the detection accuracy of temperature control during cleaning deteriorated. SUMMARY OF THE INVENTION An object of the present invention is to provide a temperature detection device which has good temperature detection accuracy and has no difference in temperature detection accuracy depending on the temperature range when detecting temperatures in different temperature ranges using the above-mentioned heat-sensitive resistance element.

0004

[Means for Solving the Problems] To achieve the above object, the present invention detects temperature using a voltage divided between a heat-sensitive resistance element whose resistance value changes depending on temperature and a resistor connected in series with the heat-sensitive resistance element. In the temperature detection device, the resistance value switching means switches the resistance value of the resistor to two or more stages, and the relationship scale between temperature and the divided voltage that changes depending on the temperature corresponds to the resistance value switching stage. and a temperature specifying means for selectively applying the relational scale according to the switching of the resistance value and specifying the temperature corresponding to the detected partial voltage. A temperature detection device characterized by:

[0005]

[Operation] According to the configuration of the present invention, when a resistor with a predetermined resistance value is connected in series to the heat-sensitive resistance element and a predetermined voltage is applied, the divided voltage between the heat-sensitive resistance element and the resistor is It is input as a voltage change due to the element changing its resistance value depending on the temperature. The device of the present invention is equipped with a relational scale storage means having at least two temperature relational scales corresponding to the input partial voltage, and the relational scale is arranged in correspondence with the resistance value switching stage for each detected temperature region. Each of the input divided voltages is amplified by changing the amplification factor, and each related scale is configured so that sufficient temperature detection accuracy can be obtained. This relational scale is switched in response to switching of the resistance value by the resistance switching means. For example, when the thermosensitive resistance element detects temperature in the detection temperature range (A) in Fig. 4, the relational scale represented by curve You can get the range. Next, when performing temperature detection in the detection temperature region (B), the resistance value switching means is used to achieve an amplification factor that obtains a divided voltage (or resistance) range of b' for a temperature range of Δt. Can be switched to resistance. For example b
If we set a resistance such that ´ is equal to a, then
Temperature detection accuracy is made almost equal regardless of the temperature range, and sufficiently high detection accuracy can be obtained in any temperature range.

[0006]

[Embodiment] Next, an embodiment in which the present invention is applied to temperature control of combustion equipment will be described. The combustion equipment is an oil fan heater, which has two temperatures: one during normal combustion to obtain the desired heating temperature, and one during cleaning to raise the temperature of the high-boiling coal that accumulates in the combustor and incinerate it. Temperature detection is performed in two temperature ranges. FIG. 2 shows an example of a combustion device for a kerosene fan heater as an explanatory diagram. Combustion oil in an oil tank 20 is sent to a vaporizer 22 by an electromagnetic pump 21, heated and vaporized by the vaporizer 22, vaporized gas is injected from a nozzle 23, and ignited by a burner 24 for combustion. A thermistor T is used as a temperature sensor for temperature control of this combustion device.
1 is attached to the carburetor 22. As described above, temperature control is performed in different temperature ranges during normal combustion and during cleaning. In the case of this combustion equipment, the temperature range during normal combustion is 250°C to 300°C, but during cleaning, the temperature range is 400°C because high boiling point charcoal is burned at high temperature.
It is carried out in the temperature range ~460°C. Therefore, the thermistor T1 performs temperature detection in the two temperature ranges mentioned above. If the point of thermistor T1 where the resistance value changes most significantly due to temperature is set during normal combustion to improve detection accuracy, the thermistor T1 will be
However, this embodiment is configured to improve the detection accuracy in both temperature ranges, although the detection accuracy is deteriorated because the resistance value is set at a point where the change in resistance value due to temperature is small. The temperature detection sensor circuit is shown in FIG.

In FIG. 1, a thermistor T1 and resistors R1 and R2 are connected in series, and the resistors R1 and R2 are connected in series.
A divided voltage based on the resistance ratio of the two combined resistances and the thermistor T1 is input to the setting circuit C1 through the protective resistor R4. Therefore, the divided voltage is input as a voltage that changes as the resistance value of the thermistor T1 changes depending on the temperature. The control circuit C1 has two relationship scales between the input partial voltage and the corresponding temperature: one for normal combustion (SC1) and one for cleaning (SC1).
2) and two prepared memories M2 are provided. These relational scales SC1 and SC2 are used to store the temperature with respect to the voltage value of the divided voltage, and the thermistor T1
When T1 is a negative characteristic thermistor, the resistance value decreases as the temperature detected by the thermistor T1 increases, so the input divided voltage becomes smaller. Regarding the resistance temperature characteristics of this thermistor, the rate of change in resistance value due to temperature differs depending on the temperature range, so in order to set the area with a high rate of change to the temperature during normal combustion, which is always used, the combined resistance of resistors R1 and R2 Set to a predetermined value. At this time, control circuit C1
is the change A in the input divided voltage as shown by the solid line in Figure 4.
Read the relational scale SC1 of temperature change to
The combustion device is controlled to maintain a predetermined heating temperature.

[0008] Next, switch S is turned on for cleaning to incinerate the high boiling point coal deposited in the combustor.
2 is closed, the control circuit C1 has resistors R3 and R
The switching voltage is input through the control circuit C1, and the relationship scale between the divided voltage and temperature is changed to the relationship scale SC in the high temperature region by the relationship scale switching circuit provided in the control circuit C1.
Can be switched to 2. Further, the control circuit C1 outputs a switching signal in response to the input of the switching voltage to operate the relay circuit C2, closes the contact S1 by the relay E1, short-circuits the voltage dividing resistor R1 with the thermistor T1, and inputs the input signal to the control circuit C1. Switch the divided voltage between the resistor R2 and thermistor T1. At this time, the relationship scale SC2 in the control circuit C1 corresponds to the temperature change by amplifying the change in the divided voltage, so that the thermistor T1 Even though the detection accuracy of the temperature detection area is poor, temperature detection can be performed with good detection accuracy. The above relationship scale is thermistor T
Two or more thermistors can be set in the temperature detectable range of 1, and the thermistor T1 in each temperature range can be set.
By changing and setting the amplification factor of the divided voltage according to the rate of change in resistance value due to temperature, and switching this using the related scale switching signal, it is possible to accurately detect a predetermined temperature in two or more temperature detection regions. Can be executed well. In the above embodiment, the switch S1 serves as the resistance value switching means.
The memory M2 serves as a relational scale storage means, and the control circuit C1
corresponds to the temperature specifying means.

[0009]

[Effects of the Invention] According to the present invention described above, it is possible to detect a predetermined temperature in at least two detection temperature ranges with high detection accuracy using one heat-sensitive resistance element. In combustion equipment that requires temperature control in a temperature range, it is possible to accurately control the temperature in any detected temperature range.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a temperature detection sensor circuit according to an embodiment.

FIG. 2 is an explanatory diagram of the configuration of a combustion device to which the present invention is applied.

FIG. 3 is a circuit diagram of a conventional temperature detection sensor circuit.

FIG. 4 is a graph showing an example of resistance temperature characteristics of a thermistor.

[Explanation of symbols]

T1...Thermistor (thermal resistance element) R1,
R2...Resistor C1...Control circuit
E1...Relay (switching means) R3, R5...Resistor (signal input means) S1...
Relay contact (switching means) S2...Switch (signal input means) C2
...Relay circuit (switching means)

Claims (1)

[Claims] Claim 1: A temperature detection device that detects temperature using a divided voltage between a heat-sensitive resistance element whose resistance value changes depending on temperature and a resistor connected in series with the heat-sensitive resistance element, wherein the resistance value of the resistor is set in two levels. Resistance value switching means for switching above,
A relational scale storage means for storing a relational scale between temperature and the divided voltage that changes depending on the temperature in a plurality of columns corresponding to the switching stage of the resistance value; 1. A temperature detection device comprising: temperature specifying means for selectively applying and specifying a temperature corresponding to a detected partial voltage.