JP2001076846A - Temperature detecting method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device capable of detecting the temperature of any portion of a heater wire with temperature detecting function and detecting overheat generated in any portion independently of a wiring pattern. SOLUTION: A cord heater 6 has a heating wire 2 and a sensor wire 4 arranged via a plastic thermistor 3, wherein a temperature detecting means 9 having an AC power supply E connected to a heating circuit with a power control element 8 connected in series to the heating wire 2 and connected to the sensor wire 4 detects a first current I1 flowing from one pole (q-phase) of the AC power supply E via the plastic thermistor 3 through the sensor wire 4 to the other pole (p-phase) and a second current I2 flowing from the other pole (p-phase) via the plastic thermistor 3 to one pole (q-phase) in a combined or averaged manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting a temperature, and more particularly to a method for controlling a heating device such as an electric blanket or an electric carpet, particularly a device for applying and controlling a full-wave AC power to a heating element. The present invention relates to an applicable temperature detection method and apparatus.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 7, a primary conductor 2 is wound on a core wire 1 made of a flexible resin such as polyester, for example, as shown in FIG. A cord heater 6 is used in which a layer of a plastic thermistor 3 is formed, a secondary conductor 4 is wound thereon, and a jacket 5 made of a flexible electric insulating material such as vinyl chloride is formed thereon.

The code heater 6 uses a plastic thermistor 3 made of a resin such as nylon which melts at a certain temperature or higher (hereinafter referred to as an overheat detection resin) to provide an overheat detection function using the primary conductor 2 or the secondary conductor 4 as a heating resistance wire. Two wires, a heater wire and a temperature detection wire, are connected to the heater by using a heater wire and a plastic thermistor 3 made of a resin whose impedance changes depending on temperature such as vinyl chloride (hereinafter referred to as temperature detection resin). It is common to do.

[0004]

As described above, in the case where the heater wire and the temperature detection line are formed as a two-piece configuration, in order to detect the temperature of the heating device over the entire length, the heater wire and the temperature detection line must be extended over the entire line. Need to be wired in parallel,
Since it is disadvantageous in terms of cost, the temperature detection line is generally sparsely wired over the entire heating surface, but it is desired to detect the temperature over the entire heater line.

[0007] Therefore, in FIG. 7, a heating resistance wire (hereinafter referred to as a heating wire in FIG. 7) is used for the primary conductor 2, and the impedance of the plastic thermistor 3 changes depending on the temperature and the temperature exceeds a certain temperature. The secondary conductor 4 may be used for temperature detection (hereinafter, reference numeral 4 is referred to as a sensor line in FIG. 7) by using a special nylon or the like that melts when the overheat and temperature are detected.

However, there is a problem in the heater wire formed in this way that also serves as a temperature detection pointed out in JP-A-63-131483. That is, it is necessary to apply a voltage between the heating wire 2 and the sensor wire 4 to measure the impedance of the plastic thermistor 3 in FIG.

Therefore, in the vicinity of at least one end of the heating wire, when the power control element (including the relay) for turning on and off the heating wire is in the ON state, the potential of the heater wire becomes substantially the same as the potential of the sensor wire. Part occurs. Therefore, even if the power control element is energized and the vicinity where the voltage becomes substantially the same is overheated, the temperature of that part cannot be detected, and finally the plastic thermistor melts, and the safety circuit operates and the energization starts. The stoppage occurs.

In view of the above, the means described in the above-mentioned publication folds a heater wire having a temperature detecting function in the center and connects it to a power supply, and always connects a heater wire having a different potential to an adjacent heating wire. Suggest to be placed,
A drawing is shown in which the two folded heater wires are spirally arranged while maintaining the same intervals. However, in the spiral heater wire wiring pattern disclosed in the above publication, it is necessary to reverse the wiring to the center of the heater wire from the center, so that it is difficult to improve the productivity.
Further, since the temperature is not detected over the entire heater wire as described above, further improvement is required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and detects a temperature of a heater wire having a temperature detecting function with high performance so that any portion of the heater wire can detect the temperature. This makes it possible to reliably detect the temperature even if any part of the heating wire is overheated with respect to an arbitrary wiring pattern, and to easily implement a safety circuit that turns off the power when the heater wire becomes overheated. It is an object of the present invention to provide a temperature detection method and an apparatus thereof that can be incorporated in a device.

[0010]

In order to achieve the above object, a temperature detecting method according to the present invention comprises a heater capable of detecting a temperature in which a heating wire and a sensor wire are arranged via a plastic thermistor. An AC power supply is connected to a heating circuit in which control elements are connected in series, and the sensor line is connected to a temperature detection unit.The temperature detection unit is connected to the sensor line via the plastic thermistor from one pole of the AC power supply. A first current flowing to the other pole and a second current flowing from the other pole to the one pole via the plastic thermistor are detected by merging or averaging.

The plastic thermistor is not particularly limited, but a resin is used in which an additive is added to a plastic thermistor, such as nylon, which melts at a constant temperature, and the amount of impedance change is increased at a temperature before melting.

The temperature detecting means includes a current detecting circuit and a current detecting circuit.
And a voltage conversion circuit, wherein the current detection circuit comprises:
A base is connected to one pole of the AC power supply, an emitter is connected to the sensor line via a diode, and a capacitor is connected between the base and the collector. A current flows to turn on the transistor, and a current discharged from the capacitor through the transistor is used as the first current, and a current obtained by combining the second current and the charging current of the capacitor is subjected to the current-voltage conversion. The voltage can be converted by a circuit.

A thermal fuse is interposed between the AC power supply and the heat generating wire, and a heat generating resistor for blowing the thermal fuse is interposed between the sensor wire and the current detecting means. A safety circuit that melts the heating circuit when the heating wire is short-circuited can be provided.

The current-to-voltage conversion circuit is formed by an integrating circuit comprising an OP amplifier provided with a negative feedback circuit in which a capacitor and a resistor are connected in parallel, and the current-voltage conversion circuit is connected to the negative feedback circuit connected to the inverting input terminal of the OP amplifier. The first and second currents may be supplied to convert the temperature of the plastic thermistor into a voltage output from the current-voltage conversion circuit.

The first current flowing through the one pole of the AC power supply
A current-voltage conversion circuit configured to supply a current by a base current supplied from the current detection circuit and a discharge current of a capacitor, and to generate the second current flowing through the other pole by an integration circuit including the OP amplifier; Supplied from
The temperature of the plastic thermistor is detected by being converted into a signal obtained by converting the second current into a voltage (hereinafter referred to as a temperature signal 2) and a signal obtained by converting the charging current of the capacitor into a voltage (hereinafter referred to as a temperature signal 1). can do.

When the current-voltage conversion circuit is an integrating circuit composed of an OP amplifier provided with the negative feedback circuit,
The temperature signal 1 and the temperature signal 2 can be taken out as an added or averaged voltage (hereinafter referred to as a temperature signal 3),
Comparing the temperature signal 3 with a set voltage corresponding to the temperature setting;
By controlling the power control element, it is possible to extract almost the same signal regardless of which potential portion of the code heater is overheated.

According to the present invention having the temperature detection circuit, a temperature fuse is interposed between the AC power supply and the heating wire,
A heating resistor for blowing the thermal fuse can be interposed between the sensor line and the current detecting means.

In order to achieve the above object, a temperature detecting device according to the present invention is a heater capable of detecting a temperature in which a heating wire and a sensor wire are arranged via a plastic thermistor, wherein a power control element is connected to the heating wire in series. An AC power supply is connected to the heat generating circuit, and the sensor line is connected to a temperature detecting means. The temperature detecting means is formed by a current detecting circuit and a current-voltage converting circuit, and the current detecting circuit is formed by a transistor base. And a collector connected between the transistor and the collector, the base is connected to one pole of the AC power supply, and the emitter of the transistor is connected to a sensor line via the diode. The circuit is formed by an integrating circuit including an OP amplifier provided with a negative feedback circuit, and the negative feedback circuit on the inverting input terminal side of the OP amplifier is provided. Are connected to the sensor line and the collector-side pole of the capacitor via diodes, respectively, and a merge of a charging current for charging the capacitor with the transistor being turned off from the integration circuit and a first current flowing to the plastic thermistor The temperature of the plastic thermistor is detected by using a current or an average current as a voltage converted by the current-voltage conversion circuit.

As means for providing a safety circuit in the device,
A thermal fuse may be interposed between the AC power supply and the heating wire, and a thermal resistor for blowing the thermal fuse may be interposed between the sensor wire and the current detecting means.

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention;

The code heater 6 capable of detecting the temperature used in the first embodiment shown in FIG. 1 is arranged on the electric carpet body 7 in a predetermined pattern (not shown).
The heating wire 2 is connected in series with a relay 8 which is a power element and connected to a commercial AC power supply (hereinafter referred to as AC power supply; one pole of the commercial power supply is p-phase and the other pole is q-phase) E. are doing. Since the internal structure of the code heater 6 is the same as that described with reference to FIG. 9, the same members are denoted by the same reference numerals and description thereof will be omitted.

The impedance of the plastic thermistor 3 between the heating wire 2 and the sensor wire 4 of the code heater 6 is generally such that the capacitance component is more dominant than the resistance component on the low temperature side. Therefore, in the first embodiment,
One terminal S1 of the sensor line 4 is connected to one p of the AC power source E.
The phase is connected via a resistor R 1, and the other terminal S 2 is connected to a temperature detection circuit 9.

In this manner, the resistor R1 can more reliably capture the change in the capacitance component of the impedance of the plastic thermistor 3 between the heating wire 2 and the sensor wire 4 of the code heater 6 facing each other. In the above description, the p and q phases are given for convenience, and may be connected to the other q phase side of the AC power supply E. In particular, when the relay 8 is off, only a positive current rectified by the diodes D2 and D4 is applied to the sensor line 4. Therefore, when the capacitance component of the plastic thermistor divided by the resistance component, the resistance changes even if the capacitance component changes. Since the discharge amount of the component cannot be exceeded, a change in the capacitance component cannot be detected. For this reason, in order to make the capacitance component sufficiently smaller than the resistance component, a resistor is connected to catch the change in the capacitance component.

The temperature detection circuit 9, a current detection circuit F and current - is composed from the voltage conversion circuit D, the current detection circuit F includes a circuit having a diode D2 to current I ₁ flows, the emitter e of the base b of the transistor Q The transistor Q is turned on by the current flowing through the capacitor C3, and the capacitor C3 connected between the base b and the collector c is discharged.
Is turned off, the transistor Q is turned off, and the charging current I supplied to the capacitor C3 through the diode D3.
₁ ' And two circuits for generating

The current-voltage conversion circuit D constitutes an integration circuit by connecting a capacitor C3 and a resistor R5 in parallel between an OP amplifier IC and an output terminal and an inversion input terminal of the OP amplifier IC. By connecting the terminal to one p-phase of the AC power supply E, the potential of the inverting input terminal is operated at the p-phase potential of the AC power supply E.

The diode D2 and the diode D3 are connected to the inverting input terminal of the OP amplifier IC, and the currents (I ₁ + I ₂ ) flowing through the diodes D2 and D3 are combined and input. I have.

Before describing the above currents, an equivalent circuit of the code heater 6 shown in FIG. 2 will be described. In FIG. 2, the plastic thermistor 3 can be represented as an equivalent circuit in which a number of resistors SR and capacitors SC that change with temperature are connected in parallel between the heating wire 2 and the sensor wire 4. Since the sensor wire 4 has a resistance value much lower than the impedance of the plastic thermistor 3, it is shown in the same manner as the conductor wire in the equivalent circuits shown in FIGS. The code heater 6 shown in FIG.
Can be further simplified to the equivalent circuit shown in FIG.

FIG. 3 shows a circuit diagram when the relay 8 is turned on using the equivalent circuit shown in FIG. FIG.
, The current flowing in the circuit changes as shown in FIG. 4 according to the alternating voltage of the AC power supply E.

When the q-phase side of the AC power supply E becomes high voltage while the relay 8 is ON (FIG. 4), the OP amplifier I
Since the inverting input terminal of C has the same potential as the p-phase, the inverting input terminal passes through the diode D2, the sensor wire 4, the plastic thermistor 3, the heating wire 2 and the q of the AC power source E.
Since the phase is blocked by the diode D2, the charging current I ₁ ^′ does not flow. However, since the emitter e of the transistor Q whose base is grounded to the q phase of the AC power supply E has substantially the same potential as the q phase, the diode D
A first current (I) from the emitter e to the p-phase of the AC power supply E through the diode D4, the sensor wire 4, the resistor R1, and the p-phase of the AC power supply E through the sensor wire 4, the plastic thermistor 3, and the heating wire 2. ₁ = | i _SR1 + i _SC1 + i
_R1 |) flows.

Most of the first current I ₁ is supplied by the charge current charged in the capacitor C 1 connected between the base b and the collector c of the transistor Q (I ₁ ≒).
I ₁ ) (supplied by 99% or more because the transistor Q is grounded at the base). Here, in the next half cycle of the AC power supply E (when the p phase of the AC power supply E becomes high voltage), a diode 3 is connected to the capacitor C1 from the inverting input terminal of the OP amplifier IC (the same potential as the p phase of the AC power supply E). Through the capacitor C1. The charge current is the same as the current discharged in the previous half cycle, that is, the current I ₁ ′ flowing from the collector c to the emitter e of the transistor Q.

When the p-phase side of the AC power source E becomes high voltage, the diode D4, the sensor wire 4, the plastic thermistor 3, the heating wire 2, or the resistor e from the emitter e of the transistor Q having substantially the same potential as the q phase of the AC power source E. the p phase of the R1 as AC power source E first current I ₁ because it is blocked by the diode D4 does not flow. However, the second current (I ₂ = I ₂ = | I _SR2 + i _SC2 |) flows. The current I flowing into the inverting input terminal of the OP amplifier IC is I = I ₁ ′ + I ₂ ≒ I ₁ + I ₂ = | i _SR1 + i _SC1 + i _R1
| + | I _SR2 + i _SC2 |.

When the relay 8 is off, the equivalent circuit is
FIG. Die from inverting input terminal of OP amplifier IC
Current I 'flowing through the ode D2_TwoRelay 8
It is zero because it is in the off state. However, q of the AC power supply E
When the phase side is high voltage, the base is grounded to the q phase of the AC current E
The emitter e of the transistor Q is at substantially the same potential as the q phase
Therefore, from the emitter e to the diode D4, the sensor
-Wire 4, Plastic thermistor 3, Heating wire 2
P-phase of AC power supply E or diode from emitter e
D4, the sensor line 4, the resistance R1, and the
The current (| I ₁= I_SR1+ I_SR2+ I_SC1+ I_SC2+
i_R1|) Flows.

The first current I ₁ is supplied from the charge current charged in the capacitor C 1 connected between the base b and the collector c of the transistor Q (I ₁ ≒).
I ₁ ) (supplied by 99% or more because the transistor Q is grounded at the base). Here, in the next half cycle of the AC power supply E (when the p phase of the AC power supply E becomes high voltage), the diode 3 is passed through the inverting input terminal of the OP amplifier IC (the same potential as the p phase of the AC power supply E) to the capacitor C1. The capacitor C1 is charged. The charge current amount is the same as the current discharged in the previous half cycle, that is, the current I ₁ ′ flowing from the collector c to the emitter e of the transistor Q.

When the p-phase side of the AC power supply E is at a high voltage, the diode D4, the sensor line 4,
The current I ′ ₁ does not flow through the plastic thermistor 3, the heating wire 2 or the resistor R _{1, and} is blocked by the diode D 4 in the p-phase of the AC power supply E. OP amplifier IC
The current I ′ flowing into the inverting input terminal of I ′ is I ′ = I ₁ ′ ≒ I ₁ = | i _SR1 + i _SC1 + i _R1 + i _SR2
+ I _SC2 |.

As described above, regardless of whether the relay 8 is on or off, the current (i _SR1 ; i _SC1 ; i _SR2 ;) corresponding to the impedance of the plastic thermistor 3
i _{SC 2} ) can be captured. That is, the temperature of any part of the code heater 6 can be detected equally.

The current I or I 'input to the inverting input terminal of the OP amplifier IC is equal to the current-voltage conversion circuit D
Accordingly, a capacitor C3 and a resistor R5 are connected in parallel between the output of the OP amplifier IC and the inverting input terminal to form an integrating circuit, and the non-inverting input terminal is connected to the p-phase of the AC power supply E. can be taken out voltage V _S corresponding to the change of the plastic thermistor 3 between the sensor line 4 and the heating wire 2 as a base point.

In addition to the present invention, the first current I ₁ can be detected by a current transformer or the like. However, in the current technology, it is not easy to accurately detect a small current with a current transformer. In addition, since the large current I _H flowing through the heating wire 2 coexists to detect on the heating wire 2 side,
Cannot be measured.

On the other hand, in the present invention, the first embodiment is shown.
As shown, the first current I₁Without measuring the condenser
C1 charging current i₁’Indirectly
The current flowing through the plastic thermistor 3 (| i
_SR1+ I_SC1+ I_R1| + | I _SR2+ I_SC2|) Or (|
i_SR1+ I_SC1+ I_R1+ I_SR2+ I_SC2Measure |)
be able to.

Next, a temperature detection method according to the second embodiment will be described with reference to FIG. The safety circuit has a power supply circuit with a thermal fuse 10 interposed therebetween, and a heating resistor HR for blowing the thermal fuse 10 between the temperature detecting circuit 9 and the code heater 6. Therefore, for some reason, the cord heater 6 is overheated, the plastic thermistor 3 is in a fusing state, and the heating wire 2 and the sensor wire 4 are short-circuited and a large current flows. It is possible to prevent dangers such as fire and burns from the heating device. Note that the symbol R in FIG.
Reference numeral 4 denotes a resistor for preventing occurrence of overcurrent when the power is turned on.

Since the large current flows through the temperature detecting circuit 9, the circuit may be damaged. Therefore, a bypass passage is provided so that the transistor Q and the OP amplifier IC are not damaged. Therefore, the diodes D5 and D6 are connected in parallel with the transistor Q, and when the large current flows, the current is bypassed through the diodes D5 and D6. Further, by connecting the diode D1 in parallel between the inverting input terminal and the non-inverting input terminal of the OP amplifier IC, it is possible to prevent the OP amplifier IC from being damaged and to supply a sufficient current to the heating resistor HR. did.
Also, a resistor R3 is attached in parallel with the capacitor C1,
When the AC power supply E was cut off, the charge of the capacitor C1 was discharged.

As described above, according to the present invention, even if any part of the code heater 6 is short-circuited or any part is locally overheated, it is possible to detect it. Need not be considered.

[0042]

As described above, according to the temperature detecting method and apparatus of the present invention, the current flowing through the plastic thermistor between the sensor wire and the heating wire of the cord heater connected to the AC power supply is supplied to either of the cord heaters. The same circuit can be detected with high accuracy in any part, and the safety circuit operates even if the code heater overheats and melts in any part of the plastic thermistor. A possible and safe heating device can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating an outline of a temperature detecting device according to a first embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of the code heater shown in FIG.

FIG. 3 is an equivalent circuit diagram obtained by further simplifying the equivalent circuit diagram shown in FIG. 2;

FIG. 4 is an equivalent circuit diagram when a power control element is turned on in the circuit shown in FIG. 1;

FIG. 5 is an equivalent circuit diagram when the power control element is turned off in the circuit shown in FIG. 1;

FIG. 6 is a circuit diagram illustrating an outline of a temperature detecting device according to a second embodiment of the present invention.

FIG. 7 is a structural explanatory view of a code heater provided with a known temperature detecting means.

[Explanation of symbols]

2 Heating wire 3 Plastic thermistor 4 Sensor wire 6 Code heater 8 Power control element 9 Temperature detecting means I ₁ First current I ₂ Second current

Claims (6)

[Claims] 1. A heater capable of detecting a temperature in which a heating wire and a sensor wire are arranged via a plastic thermistor, wherein an AC power supply is connected to a heating circuit in which a power control element is connected in series to the heating wire; Is connected to a temperature detecting means, the temperature detecting means is configured to control a first current flowing from one pole of the AC power supply to the other pole from the sensor wire via the plastic thermistor through the plastic thermistor, and the plastic thermistor from the other pole. A second current flowing from the sensor line to the one pole as described above, is combined or averaged and detected. 2. The temperature detection means is formed by a current detection circuit and a current-voltage conversion circuit, wherein the current detection circuit has a base connected to one of the poles of the AC power supply, and an emitter connected via a diode. It is formed by a transistor connected to a sensor line and having a capacitor connected between the base and the collector.Current flows from the AC power supply to the base to turn on the transistor, and the capacitor discharges and flows through the transistor. 2. The temperature detection method according to claim 1, wherein the current is the first current, and the current obtained by combining the second current and the charging current of the capacitor is converted into a voltage by the current-voltage conversion circuit. 3. A thermal fuse is interposed between the AC power supply and the heat generating wire, and a heat generating resistor for fusing the thermal fuse is interposed between the sensor wire and the temperature detecting means. Item 3. The temperature detection method according to item 1 or 2. 4. A current-voltage conversion circuit comprising an integration circuit comprising an OP amplifier provided with a negative feedback circuit in which a capacitor and a resistor are connected in parallel, wherein said negative feedback is connected to an inverting input terminal side of said OP amplifier. 4. The temperature detection method according to claim 1, wherein the first and second currents are supplied from a circuit, and the temperature of the plastic thermistor is converted into a voltage output from the current-voltage conversion circuit. 5. A heater capable of detecting a temperature in which a heating wire and a sensor wire are arranged via a plastic thermistor, wherein an AC power supply is connected to a heating circuit in which a power control element is connected in series to the heating wire, Is connected to a temperature detection means, the temperature detection means is formed by a current detection circuit and a current-voltage conversion circuit, and the current detection circuit is connected to a capacitor between a base and a collector of a transistor; Is connected to one pole of the AC power supply, and the emitter of the transistor is connected to a sensor line via the diode. The current-voltage conversion circuit is configured by an OP amplifier provided with a negative feedback circuit. The negative feedback circuit formed by an integrating circuit on the inverting input terminal side of the OP amplifier is connected to the sensor line via a diode. Connected to the collector-side pole of the capacitor, the transistor is turned off from the integrating circuit, and the combined current or average current of the charging current for charging the capacitor and the first current flowing to the plastic thermistor is converted to the current-voltage conversion. A temperature detecting device for detecting a temperature of the plastic thermistor as a voltage converted by a circuit. 6. A temperature fuse is interposed between the AC power supply and the heating wire, and a heating resistor for fusing the thermal fuse is interposed between the sensor wire and the temperature detecting means. Item 3. The temperature detection method according to item 1 or 2.