JPH07129254A - Temperature control unit - Google Patents

Abstract

PURPOSE:To provide the temperature control unit which turns OFF an electric feeding control element and also disconnects the power source path to a heater if the cable run extending to a temperature measuring circuit from a temperature measuring element is disconnected or if both end electrodes of the temperature measuring element are short-circuited as to a temperature control unit which detects the phase difference between an AC voltage applied to the temperature measuring element and an AC current flowing thereto and utilizes the phase difference as a temperature measurement signal. CONSTITUTION:When a source voltage changes into a plus half wave, a pulse voltage is generated and when the device is normal, this pulse voltage falls to the zero potential; if the cable run between both the electrodes of the temperature measuring element 5 or between the temperature measuring element 5 and temperature measuring circuit enters an abnormal state such as a disconnection and a short circuit, the pulse voltage makes a thyristor 27 conduct so that a large current flows to a resistance 10 for heat generation. A temperature fuse 2 provided in contact is fused by the heat generation of the resistance 10 for heat generation to disconnect the cable run to the heater 3. At the same time, a voltage which turns ON the electric feeding control element falls to the zero potential and the electric feeding control element 4 turns OFF.

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 using a temperature measuring element in which the phase angle of impedance changes with temperature.

[0002]

2. Description of the Related Art The phase angle of impedance of a temperature measuring element is
As an example of a temperature control device that detects a phase difference between an AC voltage applied to a temperature measuring element and an AC current flowing through the temperature measuring element and controls energization to a heater by using this phase difference as a temperature signal, Japanese Patent Application Laid-Open No. 51-25692. Japanese Unexamined Patent Publication No. 4-190581
The technique disclosed in Japanese Patent Publication is known.

[0003]

The above conventional technique detects the phase difference between the AC voltage applied to the temperature measuring element and the AC current flowing through the temperature measuring element at each zero-cross point to turn on / off the energization control element. However, it is only to control the energization of the heater.If the electric circuit from the temperature measuring element to the temperature measuring circuit is broken or both electrodes of the temperature measuring element are short-circuited, normal temperature control cannot be performed. There is a problem that the heater temperature rises abnormally and causes a burnout accident.

Furthermore, when a general commercial power source is applied to the device as an input power source for both of them, the harmonics generated in other devices superposed on the power source displace the zero-cross point from the original position and cause a true The phase difference cannot be detected.
In particular, as a temperature measuring element, the heat-sensitive wire whose capacitance and resistance change according to temperature acts as a high-pass filter, so the current flowing through it is affected by harmonics and its zero-cross point Is further deviated and the control temperature becomes unstable, which is a fatal problem.

The present invention solves the above-mentioned problems of the prior art, and detects the phase difference between the voltage applied to the temperature measuring element and the current flowing through it, and uses this as a temperature measuring signal for temperature control. It is an object of the present invention to provide a temperature control device that shuts off the power supply to a heater when the electric path from the temperature measuring element to the temperature measuring circuit is broken or when both electrodes of the temperature measuring element are short-circuited.

Another object of the present invention is to provide an apparatus capable of detecting the phase difference and stably controlling the heater temperature without being affected by the harmonics superposed on the input power source. Still another object of the present invention is that the current flowing through the temperature measuring element is the same with respect to the positive and negative of the AC waveform, and the characteristics of the temperature measuring element do not change over time, and the temperature can be controlled accurately and stably over a long period of time. The purpose is to provide a device that can.

[0007]

In order to achieve the above-mentioned object, the present invention provides a temperature control device using a phase difference between an AC voltage applied to a temperature measuring element and a current flowing therein as a temperature measuring signal. A high cut filter is provided in the preceding stage of the temperature measuring circuit of the apparatus, so that the electric power supply to the heater is cut off when the temperature measuring element and the temperature measuring circuit are disconnected from each other or when both electrodes of the temperature measuring element are short-circuited.

The bases of the NPN transistor and the PNP transistor are connected to one electrode of the temperature measuring element, and the emitters of both transistors are connected to one of the power supplies.
One of the capacitors is connected to the part where two Zener diodes are connected to the power source with opposite polarities, and between the other side of the capacitor and one of the power sources, the capacitor is charged when the negative half wave of the AC power source is applied. , Two diodes are provided so that they are discharged when a positive half-wave is applied.

When the zero cross point of the current flowing through the temperature measuring element approaches the zero cross point of the voltage applied to the temperature measuring element,
The gate potential of the energization control element is clamped to zero, and at the same time, a sufficient current is supplied to the heating resistor connected in parallel with the AC power source to generate heat. The heat generating resistor is in contact with a thermal fuse provided in the power supply path. Further, the operation indicator lamp is connected in series with the heating resistor to the AC power source.

[0010]

[Function] A positive current flows through the temperature measuring element, and the capacitor is charged while a negative voltage is applied at the same time. When a positive voltage is applied to the temperature measuring element, a reverse potential is applied to the capacitor. The charge is discharged through the diode. The energization control element turns on according to the magnitude of this discharge energy.
Turn off to control energization to the heater.

A positive alternating current with respect to the temperature measuring element is the temperature measuring element to the base to the emitter of the NPN type transistor, and a negative alternating current is the emitter to the base of the PNP type transistor to the base.
Flowing with the temperature measuring element, the temperature measuring element does not generate an unbalanced component with respect to the positive / negative of AC, and the temperature measuring element does not change with time. Further, the harmonics superposed on this alternating current are removed by the high cut filter, the fluctuation of the power supply voltage is made constant by the Zener diode, the charge and discharge of the capacitor are stabilized, and the temperature signal is not affected by the harmonics.

When the electric circuit between the temperature measuring element and the temperature measuring circuit is broken or the electrodes at both ends of the temperature measuring element are short-circuited, the gate potential of the current control element becomes zero, the current control element is turned off, and the heater is energized. Is cut off. Further, the thermal fuse is blown by the heat generated by the heating resistor, and the power supply to the control device and the heater is cut off.

[0013]

1 is a circuit diagram of an apparatus according to the present invention, in which a temperature fuse 2, a heater 3 and an energization control element 4 are connected in series to an AC power supply 1 to form a heater power supply path. Temperature measuring element 5
Is a pair of conductors 5a and 5b filled with a thermistor layer 5c whose phase angle changes according to temperature.
Is provided close to. One conductor 5a is one end 1a of the power source
On the other hand, the other conductor 5b passes through resistors 6, 7 and 8 and the other end 1b of the power source.
Connected to the resistors 6 and 7 and the other end 1b of the power supply.
A capacitor 9 is connected between them to form a high cut filter. The thermistor layer 5c of the temperature measuring element 5 is made of a flexible polymer compound, and conductors 5a and 5b having an arbitrary shape such as a linear shape, a planar shape or a mesh shape are used as electrodes and filled between them.

The Zener diodes 12 and 13 have their respective cathodes on the side of the power sources 1a and 1b, and have a heating resistor 10 and a resistor 1 respectively.
1 is connected in series to the power source 1, and a capacitor 14, a diode 15 having a cathode on the side of the capacitor 14 and a resistor 16 are connected in series between both anode connections A and the power source 1b. The base of the transistor 17 is the resistors 7 and 8
In the meantime, the collector is connected to the connection portion A, and the emitter is connected to the other end 1b of the power supply. The capacitor 14 has a diode 1 whose anode is the side of the capacitor 14.
A series circuit of 8, a variable resistor 19 and a resistor 20 is cascade-connected. Further, resistors 21 and 22 are cascade-connected to the mover of the variable resistor 19, and both resistors 21 and 2 are connected.
The gate of the energization control element 4 is connected to the connection portion of 2.

A capacitor 23 and a resistor 24 are connected in series between the cathode side of the Zener diode 12 and the power source 1b, and a diode 25 and a resistor 26 are cascade-connected at the connection between the capacitor 23 and the resistor 24.
The cathode of 5 is the gate of the thyristor 27 and the resistor 28.
The other end of the resistor 28 is connected to the collector of the NPN transistor 29, respectively. A capacitor 30 is provided between the base and the emitter of the transistor 29.
Is connected to the base of the transistor 17, and the emitter of the transistor 29 is connected to the other end 1b of the power source. The bases of the transistor 29 and the transistor 17
The emitters have the same impedance with respect to the positive and negative currents flowing through the temperature measuring element 5.

A series circuit of a diode 31 and a thyristor 27 is cascade-connected between the connection between the heating resistors 10 and 11 and the other end 1b of the power supply, both of which have their cathodes on the side of the other end 1b of the power supply. Further, a diode 32 having the same direction polarity is interposed between the anode of the thyristor 27 and the cathode of the diode 15. Also, the heating resistor 1
A resistor 33 and a light emitting diode 34 are provided between 0 and the other end 1b of the power source.
Are connected in series, and a diode 35 is connected in parallel to the light emitting diode 34. Further, a varistor 36 is connected to the power supply 1 to absorb an abnormally high voltage and protect the device.

FIG. 2 shows another embodiment of the present invention, which is shown in FIG.
The safety circuit section and the drive circuit section are modified as follows by removing the diodes 31 and 32 shown in FIG. To change the safety circuit part, the resistor 28 is released from the gate of the thyristor 27, the diode 37 is provided between the connection part between the capacitor 23 and the resistor 24, and the emitter of the PNP transistor 38 is provided between the capacitor 14 and the diode 18. ~ The collector is connected and the base is connected to the transistor 2 via the resistor 39.
9, and a resistor 40 is connected between the base and emitter of the transistor 38. Incidentally, FIG.
Then, the one electrode 5a of the temperature measuring element 5 of FIG.

The drive circuit section is changed by changing the energization control element 4 from a one-way thyristor to a two-way thyristor by changing the power supply 1
A capacitor 41, a resistor 42, a diode 43, and a thyristor 44 are connected in series between a and 1b.
Is connected between the resistors 21 and 22. Further, the diode 43 is provided at the connection portion between the heater 3 and the energization control element 4.
The diode 45 is connected to the cathode of the same, the resistor 46 is connected to the anode of the same, and the gate of the conduction control element 4 is connected to the anode of the thyristor 44.

FIG. 3 is a diagram for explaining the operation of the temperature measuring circuit section. FIG. 3A is a waveform diagram of the voltage v applied to the transistor 17 and the flowing current i. The voltage v is the zener diode 12. , 13 to a constant voltage, the current i is a resistor 6,
The harmonic component contained in the power supply is removed by the capacitor 7 and the capacitor 9. FIG. 8 shows the temperature of the temperature measuring element 5.
An example of the phase angle characteristic is shown, and the phase angle φ becomes smaller on the high temperature side. The change in the phase angle φ and the phase difference φ ′ between the voltage v and the current i
Since it corresponds to the change in the temperature difference, the temperature can be known by measuring the phase difference φ ′.

If the zener voltages of the zener diodes 12 and 13 are selected to be about 15 volts, the threshold voltage of the transistor 17 (0.7 volts or less) can be ignored.
The time width φ1 in which the voltage v becomes zero volts after the transistor 17 is turned off substantially corresponds to the phase difference φ ′ between the voltage v and the current i. FIG. 3B is an operation diagram of the transistor 17, FIG.
3C is a voltage at point A, FIG. 3D is a voltage at point B, and FIG.
(E) shows the voltage at the point C, and the point A is a negative voltage (corresponding to φ1), the capacitor 14 is charged through the resistor 16 and the diode 15, and when the voltage v changes to positive, the capacitor 14 becomes The reverse voltage is applied and the charging charge is diode 1
8 is discharged through the variable resistors 19 to 20. By adjusting the discharge voltage with the mover of the variable resistor 19, the energization control element 4 is turned on / off to control the energization of the heater 3.

In FIG. 2, when the power supply voltage is a positive half-wave, a current flows through the path of the heater 3, the resistor 46, and the gate of the conduction control element 4 to turn on the conduction control element 4. At this time, a current simultaneously flows in the path of the capacitor 41 to the resistor 42 to the diode 45, and the capacitor 41 is charged. When the power supply voltage changes to a negative half-wave and the energization control element 4 is turned off, the charge charged in the capacitor 41 is stored in the anode of the energization control element 4 through the anode.
Discharged in the path of gate-diode 43-resistor 42,
The energization control element 4 is turned on again. When the energization control element 4 is turned on, the current flowing through the temperature measuring element 5 decreases, so that
As indicated by the broken line, the off-point of the transistor 17 moves and the phase difference becomes φ2, which causes an appropriate amount of hysteresis.

FIG. 4 is for explaining the operation of the safety circuit shown in FIG. 1. FIG. 4 (a) is a waveform diagram of the voltage V applied to the temperature measuring element 5 and the current I flowing through it, and FIG. 4B shows the voltage at the point D, and FIG. 4C shows E when the transistor 29 is not provided.
4D shows the operation voltage of the transistor 29, and FIG. 4E shows the gate voltage of the thyristor 27.

When the power supply voltage V is a positive half-wave, the voltage at point D rises to the Zener voltage of the Zener diode 12 (FIG. 4 (b)).
(Refer to FIG. 4C) and differentiated by the capacitor 23 and the resistor 24. The charged electric charge of the capacitor 23 at this time is the resistance 1 at the next negative half wave.
It is discharged through the paths 1, 10, and 24. The positive voltage pulse tries to turn on the thyristor 27 by triggering the gate of the thyristor 27 through the diode 25, but if the transistor 29 is in the on state at this time, the thyristor 27 is turned on.
Do not turn on.

Since the capacitor 30 connected to the base of the transistor 29 turns on the transistor 29 slightly after the positive rise of the current flowing through the temperature measuring element 5, the transistor 29 is turned off when the power supply voltage V rises positively. In either state, that is, when the electrodes at both ends of the temperature measuring element 5 are short-circuited and the phase difference φ is zero, or when the electric path F is broken or the lower end of one electrode 5b of the temperature measuring element 5 and the electric path G are short-circuited. In the case of, the thyristor 27 is turned on. When the thyristor 27 is turned on, the point B is dropped to the zero potential through the diode 32, so that the conduction control element 4 is turned off and the diode 3 is turned on.
An equivalent current flows through the heat generating resistor 10 via 1 to generate heat, and the thermal fuse 2 is melted to cut off the power supply to the heater 3 and the entire device. Since the resistance value of the resistor 11 is designed to be several tens of times larger than that of the resistor 10, a sufficient current does not flow for the heating resistor 10 to generate heat when the thyristor 27 is off. The time when the transistor 29 is turned on with a delay is changed by the constant of the capacitor 30.

The operation of the safety circuit shown in FIG. 2 is as follows. When the device is normal, the capacitor 14 is turned on while the transistor 29 is on (transistor 17 is off).
When the diode 18 side of becomes positive, the capacitor 14
A part of the electric charge of the above flows to the emitter to the base of the transistor 38 to turn on the transistor 38, and the electric charge of the capacitor 14 flows to the variable resistor 19 via the diode 18 to perform the above operation.

When the wire F from the temperature measuring element 5 to the temperature measuring circuit is broken or the lower end of the one electrode 5b of the temperature measuring element when the heater 3 is energized is short-circuited with the electric path G, the transistor 29 is turned off and the transistor 38 is also turned off. The path through which the capacitor 14 discharges through the diode 18 is broken. Therefore, no current flows through the variable resistor 19 and neither the thyristor 44 nor the conduction control element 4 is turned on. At the same time, the pulse voltage obtained by differentiating the voltage at point D passes through the diode 25 and passes through the thyristor 2.
Since 7 is triggered, an equivalent current flows through the heating resistor 10 to generate heat as in the above, and the thermal fuse 2 is blown.

When the phase difference φ is zero, the transistor 29
Is turned on with a positive half-wave, but at that time, since the capacitor 14 is not charged, the transistor 38 cannot be turned on, and similarly to the above, neither the thyristor 44 nor the conduction control element 4 is turned on.

FIG. 5 shows another embodiment of the temperature measuring circuit section,
A resistor 50 and a variable resistor 19 connected in series are connected between the collector and the emitter of the transistor 17, and one end of the resistor 16 is connected to a mover of the variable resistor 19.

FIG. 6 shows still another embodiment of the temperature measuring circuit section, in which the temperature between the collector and the emitter of the transistor 17 is
The emitter and collector of another NPN transistor 51 are connected in parallel, a resistor 53 is connected between the base of the transistor 51 and the diode 52, and a resistor 54 is connected between the base of the transistor 51 and the emitter of the same 51, and the power supply voltage is positive. Immediately after the half-wave, the transistor 51 is turned on to form a discharge path for the capacitor 14.

FIG. 7 shows another embodiment of the drive circuit section,
The base of the NPN transistor 55 and the collector of the PNP transistor 56 are connected between the resistors 21 and 22, the collector of the transistor 55 is the base of the transistor 56, and the collector of the transistor 55 and the transistor 5 are connected.
A capacitor 57 and a resistor 58 are connected in parallel between the six emitters to form a self-holding circuit. A diode 59 is interposed in the self-holding circuit so that the positive half wave of the power supply 1 is applied.

When the transistor 55 is turned on by the current from the variable resistor 19 when the power source 1 has a positive half-wave, a base current flows through the transistor 56 to turn it on, and when the transistor 56 is turned on, a current flows to the base of the transistor 55. Even if both transistors 55 and 56 flow to turn on and the current stops flowing from the variable resistor 19 to the resistor 21, this state is maintained. When the transistors 55 and 56 are turned on, the energization control element 4 is turned on for one cycle of the power supply 1 and the power supply path of the heater 3 is closed as described above. When the energization control element 4 is turned on, no voltage is applied to the transistors 55 and 56 and they are turned off, and the standby state is set. The harmonics superposed on the power source 1 are removed by the high cut filter of the capacitor 57 and the resistor 58, and the self-holding circuit does not affect the harmonics and operates accurately.

[0032]

As described above, according to the present invention, a pulse voltage is generated when the power supply voltage changes to a positive half-wave, and an electric circuit is provided between both electrodes of the temperature measuring element or between the temperature measuring element and the temperature measuring circuit. When this is normal, the pulse voltage is dropped to zero potential, and if the electrical path between the electrodes of the temperature measuring element or the electric circuit between the temperature measuring element and the temperature measuring circuit becomes abnormal due to disconnection or short circuit, the pulse voltage is applied to the heating resistor. Since the thyristor is triggered so that a large current flows, the temperature fuse provided in the power supply path is blown to shut off the power supply to the heater and the control device, thereby preventing a burnout accident due to an abnormal temperature rise of the heater. If the heating resistor is disconnected, the light emitting diode will turn off.
A preliminary check of the heating resistor can be done visually.
At this time, the device does not operate, so double safety is achieved.

Further, when the electric path between the electrodes of the temperature measuring element or between the temperature measuring element and the temperature measuring circuit is in an abnormal state such as disconnection or short circuit, at the same time, the voltage output for turning on the energization control element is also cut off. Fail-safe is ensured.

When the harmonics are superposed on the AC power supply, the influence on the collector voltage of the phase difference detecting transistor is removed by the Zener diode, and the influence on the base current is removed by the high cut filter which is a combination of the resistor and the capacitor. Therefore, the detection of the phase difference which becomes the temperature signal and the energization control to the heater by this are accurate and stable without being affected by the above-mentioned harmonics.

Further, the positive half-wave of the alternating current to the thermistor layer of the temperature measuring element flows from the base to the emitter of the NPN type transistor, and the negative half-wave flows from the emitter to the base of the PNP type transistor. In the thermistor layer composed of, there is no unbalanced component with respect to the AC waveform, and there is no change over time.

Furthermore, the electric charge charged in the capacitor as the temperature measurement signal in the time width corresponding to the phase difference is discharged by applying an alternating reverse voltage to the capacitor, so that the discharge energy is large and the detected phase difference is Even a small drive circuit can be controlled.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a temperature control device according to the present invention.

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

FIG. 3 is a waveform diagram for explaining the operation of the temperature measuring circuit section of the device of the present invention.

FIG. 4 is a waveform diagram for explaining the operation of the safety circuit section of the device of the present invention.

FIG. 5 is a main part circuit diagram showing another embodiment of the temperature measuring circuit part of the device of the present invention.

FIG. 6 is a main part circuit diagram showing still another embodiment of the temperature measuring circuit part of the device of the present invention.

FIG. 7 is a main part circuit diagram showing another embodiment of the drive circuit part of the device of the present invention.

FIG. 8 is an example diagram of temperature-phase angle characteristics of a temperature measuring element.

[Explanation of symbols]

1 AC power supply 2 Temperature fuse 3 Heater 4 Energization control element 5 Temperature measuring element 6, 7, 8, 11, 16, 20, 21, 22, 24, 2
6,58 Resistance 9,14,23,30,41,57 Capacitor 10 Heat generation resistance 12,13 Zener diode 15,18,25,31,32,35,43,45,5
9 diode 19 variable resistance 17, 38, 56 PNP type transistor 29, 51, 55 NPN type transistor 27, 44 thyristor 34 light emitting diode

[Procedure amendment]

[Submission date] July 4, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

Another object of the present invention is to obtain a device capable of detecting the phase difference and stably controlling the heater temperature without being affected by the harmonics superposed on the input power supply. Still another object of the present invention is that the current flowing through the temperature measuring element is the same with respect to the positive and negative of the AC waveform, and the characteristics of the temperature measuring element do not change over time, and the temperature can be controlled accurately and stably over a long period of time. Is to get a device that can.

Claims (10)

[Claims] 1. A temperature measuring circuit detects a phase difference between an AC voltage applied to a temperature measuring element and an AC current flowing through the temperature measuring element to generate a temperature measuring signal, and the heater is energized corresponding to the temperature measuring signal. In a temperature control device controlled by a control element, the temperature control is characterized in that energization to a heater is cut off when the electric path between the temperature measuring element and the temperature measuring circuit is broken or a short circuit occurs between both electrodes of the temperature measuring element. apparatus. 2. When the electric path between the temperature measuring element and the temperature measuring circuit is broken or the electrodes at both ends of the temperature measuring element are short-circuited, a sufficient current flows through a heat generating resistor connected in parallel to an AC power source to generate heat. The temperature control device according to claim 1, wherein a temperature fuse provided in the power supply path is blown by the heat generation to shut off the power supply to the heater and the device. 3. The temperature control device according to claim 1, wherein the energization control element is turned off when the electric path between the temperature measuring element and the temperature measuring circuit is broken or a short circuit occurs between both electrodes of the temperature measuring element. 4. The temperature according to claim 1, wherein the alternating current flowing through the temperature measuring element flows through a circuit having the same impedance with respect to the positive and negative of the alternating current so that an unbalanced component does not occur in the alternating current waveform. Control device. 5. The temperature control device according to claim 1, wherein a high-cut filter is provided in front of the temperature measuring circuit. 6. A phase difference between a zero cross point of an alternating voltage applied to the temperature measuring element and a zero cross point of an alternating current flowing through the temperature measuring element when one half wave of an alternating current power source is applied to the temperature measuring element. The capacitor is charged for a predetermined time, and when the other half wave of the AC power source is applied to the temperature measuring element, the electric charge charged in the capacitor is discharged through the diode to control the energization control element. The temperature control device described. 7. The temperature control device according to claim 6, wherein the capacitor is discharged by applying the other half-wave of an AC power supply to the capacitor. 8. A self-holding circuit in which a pair of transistors are combined is provided between the diode and the conduction control element, and power is supplied to the self-holding circuit through another high-cut filter. The temperature control device according to claim 6. 9. The temperature control device according to claim 1, wherein the temperature measuring element has a flexible structure in which a thermistor layer of a polymer compound is filled between a pair of conductors. 10. The temperature control device according to claim 1, wherein the heater uses one of a pair of conductors filled with a thermistor layer.