JPH0756644A - Temperature controller - Google Patents

Abstract

PURPOSE:To detect a phase difference without receiving any influence of the high frequency superposed on an AC power supply and to control the heater temperature with high accuracy by dividing the voltage of the AC power supply by a resistor and a capacitor which are connected in series to the power supply and detecting the phase difference of a temperature measuring element by means of the divided voltage. CONSTITUTION:The high frequency superposed on an AC power supply 1 is eliminated by a resistor R and a capacitor C1 connected in series to the supply 1. The both-end voltage of the capacitor C1 where the power voltage is divided is further divided by two resistors R1 and R2. One of both divided voltage is applied to a temperature measuring element 10, and the other divided voltage is applied between the collector and the emitter of a transistor TR Q1. A base current flows to the TR Q1 when a positive half-wave current flows through the element 10. Then the divided voltage of the supply 1 is applied to the collector of the TR Q1 when a negative half-wave current is applied to the element 10. Thus the time width equivalent to the phase difference corresponding to the temperature of the element 10 is acquired at the collector side of the TR Q1 in each cycle of the supply 1 regardless of the size of the heat- sensitive layer of the element 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting the phase angle of a temperature measuring element to control the temperature.

[0002]

2. Description of the Related Art As an example of a device for controlling a heater temperature by detecting a phase difference between a voltage applied to a temperature measuring element such as a heat sensitive wire and a current flowing through the temperature measuring element, an example of an apparatus for controlling a heater temperature is disclosed in JP-A-3-77.
Techniques disclosed in Japanese Patent No. 036 and Japanese Utility Model Laid-Open No. 3-82412 are known.

[0003]

The above-mentioned conventional technique for detecting the phase difference between the zero point of the voltage applied to the temperature measuring element and the zero point of the current flowing through the temperature measuring element with the AC power supply as the reference voltage and controlling the temperature is known. When the power supply is a commercial power supply, harmonics generated from another electric device are superimposed on the AC power supply, and the zero point is deviated from its original position due to the influence, which makes accurate temperature detection and control impossible. When the temperature measuring element is broken or short-circuited, the control element continues to be turned on and the heater temperature rises abnormally to cause a burnout accident.

According to the present invention, the phase difference between the voltage and the current applied to the temperature sensing element is detected without being affected by the harmonics superposed on the AC power source and regardless of the dimensional accuracy of the thermosensitive wire as the temperature measuring element. It is an object of the present invention to obtain a temperature control device which controls the temperature with high accuracy, stops the energization of the heater when the temperature measuring element is broken or short-circuited, and returns to normal operation when the broken or short-circuited state is resolved, with an extremely simple structure. And

Another object of the present invention is to provide a safe temperature control device which can use a component having a low withstand voltage standard value and which stops the energization of a heater when a major component fails. It is to be.

[0006]

In order to achieve the above-mentioned object, the present invention is to connect a resistor and a first capacitor in series to an AC power source, divide the voltage across the first capacitor, and divide the voltage across the first transistor. The temperature measuring element is connected in series to the source-emitter in which the first diode is connected in parallel with the opposite polarity, and the partial pressure of one of the above is applied, and the other partial pressure is in series with the emitter-collector of the first transistor. The phase difference between the AC voltage applied to the temperature measuring element and the current flowing through it is applied as a temperature measuring signal from the collector side of the first transistor. The second transistor is input through the second capacitor, and the operation of the second transistor corresponding to the charging and discharging of the second capacitor controls the ON / OFF of the control element to control the energization of the heater. That.

When the thyristor as the control means is short-circuited, the temperature fuse provided in the power supply path is blown, so that a diode and a heating resistor are connected in series between the anode side of the thyristor and one end of the AC power supply.

The heater is provided with a sensing conductor via a melting layer, and when the melting layer is melted and the heater and the sensing conductor are short-circuited, the temperature fuse provided in the power supply path is blown. Another heating resistor is connected in series between the other ends of the.

Further, in order to turn on the thyristor as the control means, the current flowing from the collector to the emitter of the second transistor is a constant electric charge obtained by rectifying and charging the AC power supply. For the reason described later, a Zener diode is provided between the collector of the second transistor and the other end of the AC power source, and a resistor is cascade-connected to the base of the second transistor.

[0010]

The harmonics superposed on the AC power supply are removed by the resistor and the capacitor connected in series to the power supply, and the voltage across the capacitor obtained by dividing the power supply voltage is further divided by two resistors. One partial pressure is applied to the temperature measuring element,
The other partial voltage is applied to the collector-emitter of the first transistor.

When a positive half-wave current flows through the temperature measuring element,
When a base current flows through the first transistor and a negative half-wave is applied to the temperature measuring element, a voltage corresponding to the AC power source is applied to the collector of the first transistor, and the voltage is measured regardless of the size of the thermosensitive layer of the temperature measuring element. A time width corresponding to the phase difference corresponding to the temperature of the temperature element is obtained on the collector side of the first transistor for each cycle of the power supply. When the temperature measuring element is broken, the base of the first transistor does not conduct, and when the temperature measuring element is short-circuited, the phase difference becomes zero and the collector output of the first transistor cannot be obtained. Also in the case of (2), neither the second transistor in the next stage nor the control means is turned on, and the power supply path of the heater is not closed.

As described above, the collector output of the first transistor disappears due to the disconnection or short circuit of the temperature measuring element, but under these conditions, overload is not applied to each part and the parts are not destroyed. When this disconnection or short-circuit state is resolved, the operation of the first transistor returns to normal, and the heater is controlled to the set temperature.

When the melting layer is melted due to local overheating of the heater and the heater and the detection conductor are short-circuited or the thyristor of the control means is short-circuited, the heat-generating resistor generates heat to melt the temperature fuse of the power supply line, Power to the heater is stopped.

When the second transistor is short-circuited, a sufficient current for turning on the thyristor of the control means does not flow in the second transistor. Further, when the movable element of the variable resistance has poor contact, the second transistor is completely turned off.

[0015]

1 is a circuit diagram of an apparatus according to the present invention, in which a temperature fuse 2, a heater 3 and a thyristor 4 are connected in series to an AC power source 1 to form a heater power source path. A resistor R and a capacitor C1 are connected in series to the power source 1, and another resistor R1 and R2 connected in series are connected in parallel to the capacitor C1. One end a of the capacitor C1 and both resistors R1,
The temperature measuring element 10 and the base-emitter of the transistor Q1 are connected in series to the connection portion d of R2. A diode D1 is connected in parallel to the base to the emitter of the transistor Q1 in reverse polarity, and a diode D2 and a resistor R3 are connected in series between the collector of the transistor Q1 and the other end b of the power supply 1. The temperature measuring element 10 is provided close to the heater 3.

The anode side of the diode D2 and the other end b of the power source
A capacitor C2 and a diode 6 are connected in series between
A variable resistor 7 connected in series is provided on the cathode side of the diode 6.
And resistor 8 are cascaded. The base of the transistor Q2 is connected to the mover of the variable resistor 7 through the resistor 9, and the resistor 12 is connected between the emitter of the transistor Q2 and the other end b of the power source.
Are connected, and the emitter is connected to the gate of the thyristor 4. A diode 13 and a resistor 14 are connected in series on the collector side of the transistor Q2 and the anode side of the thyristor 4. A Zener diode 15 is connected between the collector of the transistor Q2 and the other end b of the power supply.

A diode 16 and a heating resistor 17 are connected in series between the anode side of the thyristor 4 and one end c of the power supply, and the detection conductor 5 and the other end of the power supply which are arranged on the heater 3 via the melting layer 11. Another heating resistor 18 is connected in series between b, and both resistors 17 and 18 are provided close to the thermal fuse 2. A resistor 19 and a light emitting diode 20 are connected in series between the cathode side of the diode 16 and the other end b of the power supply. The diode 21 is the light emitting diode 20.
, And the resistor 22 is for stabilizing the operation of the transistor Q1.

FIG. 3 shows the voltage v applied to the temperature measuring element 10.
With the waveform of the current i flowing through it (shown as a sine wave for convenience of explanation), the voltage v is obtained by dividing the voltage E of the AC power supply 1 by the resistor R and the capacitor C1 and further dividing it by the resistors R1, R2. The voltage across the resistor R1 causes the current i to have a positive half-wave (time t
(Between 1 and t3) temperature measuring element 10 to transistor Q1
In the circuit of the base-the emitter of the same-resistor R2, the base current flows through the transistor Q1, while when the voltage v is a negative half-wave (time ... T2, between t5 and t6), the diode D2 becomes conductive and the transistor Q1. A negative half-wave of the voltage across the resistor R2 is applied to the collector of the.

As shown in FIG. 4, the collector current Ic of the transistor Q1 flows between the zero point of the current i and the zero point of the voltage V (t1 to t2, t5 to t6). The section in which the collector current Ic flows corresponds to the phase difference φ between the voltage v applied to the temperature measuring element 10 and the flowing current i in a ratio of 1: 1, and the detection of the phase difference φ changes according to the temperature. It corresponds to the phase angle φ of the temperature measuring element 10.

This collector current Ic is supplied to the other end b of the power source, the diode 6, the capacitor C2, the diode D2, the collector of the transistor Q1, the emitter thereof, the resistor R1 and the resistor R.
~ Flows in the path of the power supply end c and charges the capacitor C2. When the voltage v becomes a positive half-wave, the collector current IC stops flowing, and the charge charged in the capacitor C2 is discharged through the variable resistors 7 to 8 to the resistor R3.

At this time, when the discharge voltage of the capacitor C2 exceeds the voltage required for the operation of the transistor Q2, the charge of the capacitor C2 changes from the variable resistor 7 to the resistor 9 to the transistor Q.
2 also discharges in the path of the base, the emitter, the resistor 12 and the resistor R3. Therefore, the collector-emitter of the transistor Q2 becomes conductive, a current flows through the gate of the thyristor 4 to make the thyristor 4 conductive, and the half wave of the AC power supply 1 is applied to the heater 3. Since the voltage charged in the capacitor C2 changes depending on the temperature of the temperature measuring element 10 and the adjustment of the variable resistor 7,
With these, the heater 3 can be maintained at a predetermined temperature.

If the line between the one end a of the capacitor C1 to both conductors 10a and 10b of the temperature measuring element 10 to the base of the transistor Q1 is disconnected, the transistor Q1 does not conduct, the capacitor C2 is not charged, and the transistor Q2 is not charged. And the thyristor 4 is not turned on. Further, when the thermosensitive layer 10c of the temperature measuring element 10 is short-circuited by the conductors 10a and 10b on both sides due to melting due to an abnormally high temperature, the phase difference φ becomes zero, the capacitor C2 is not charged, and the transistor Q2 and the thyristor 4 are turned off. Keep the state. These wire breaks,
When the short circuit is resolved, the operation returns to normal.

When the thyristor 4 is short-circuited, a half wave of the power source 1 flows through the thyristor 4 to the diode 16 to the heating resistor 17 to heat the resistor 17, and the thermal fuse 2 is melted to blow the power source of the heater 3. The road is cut off. Heating resistor 17
Since the light emitting diode 21 and the light emitting diode 21 are connected in series to the power source 1, the disconnection of the resistor 17 can be checked when the light emitting diode 21 does not light up. Since the resistance value of the resistor 19 is 40 times or more that of the resistor 17 for heat generation, the current required for heat generation does not flow during normal operation. When the melting layer 11 is melted due to abnormal overheating or the like and the detection conductor 5 is short-circuited to the heater 3, the other heating resistor 18 generates heat and the temperature fuse 2 is melted and the power supply path of the heater 3 is cut off.

When the temperature-phase angle characteristic of the temperature measuring element 10 becomes small on the high temperature side as shown in FIG. 5, the charge amount of the capacitor C2 necessary for conducting the transistor Q2 to the thyristor 4 is not charged. The rise in the temperature of the heater 3 is completely safe because it is not pressed down and poses a danger to the body or does not reach a high temperature leading to a burn injury.

The Zener diode 15 lowers the voltage applied to the collector of the transistor Q2 when the transistor Q2 is off, and the transistor Q2 having a low withstand voltage standard.
Enable the use of

FIG. 2 shows another embodiment of the present invention, in which a power supply path to the resistor R1 is formed from one end a of the capacitor C1 through one conductor 10a of the temperature measuring element 10.
When a is disconnected, the transistor Q1 does not conduct. Also,
A power supply path to the resistor R3 on the collector side of the transistor Q1 is formed via the other end of the power supply b, the heating resistor 18 and the detection conductor 5, and the heating resistor 18 or the detection conductor 5 is formed.
Is disconnected, the transistor Q1 does not conduct. Therefore,
In the case of both of the above, the transistor Q2 and the thyristor 4 in the next stage are not turned on and the power is not applied to the heater 3, so that safety is ensured. Since the resistance value of the resistor R3 is 40 times or more that of the resistor 18 for heat generation, the current required for heat generation does not flow during normal operation.

Further, a resistor 23 is provided between the collector of the transistor Q2 and the diode 13, and the diode 13
A capacitor 24 and a Zener diode 25 are connected in parallel between the cathode and the other end b of the power source. The resistance value of the resistor 14 is set so that the thyristor 4 does not turn on when the collector and the emitter of the transistor Q2 are short-circuited. Under normal conditions, the transistor Q2 turns on and the charge stored in the capacitor 24 is charged by the thyristor. The thyristor 4 is turned on by being supplied to the gate of No. 4. On the other hand, when the transistor Q2 is short-circuited, the capacitor 2
4 is not charged enough to turn on the thyristor 4, and the heater 3 is not supplied with power.

A resistor 26 is cascade-connected to the base of the transistor Q2 to surely turn off the transistor Q2 when the mover of the variable resistor 9 has a poor contact.
The diode 27 provided between the heater 3 and the thyristor 4 is
This is for protecting the thyristor 4 when the power source 1 has a negative half-wave.

[0029]

As described above, according to the present invention, the AC power source is divided by the resistor and the capacitor connected in series, and the phase difference of the temperature measuring element is detected by utilizing the divided voltage across the capacitor. , The harmonics superposed on the AC power supply are removed by the filter with these resistors and capacitors, and the zero point of the voltage applied to the temperature measuring element and the zero point of the flowing current are not affected by the harmonics, so the phase difference as the temperature measuring signal Can be accurately detected, and temperature control in the subsequent stage based on this can be performed with high accuracy.

Further, the temperature measuring element and the phase detection transistor are applied with a low voltage obtained by dividing the voltage of the AC power source, which is divided by the resistor and the capacitor, by two resistors. Voltage can be used to provide the entire device in a compact and inexpensive manner, and even if the temperature measuring element is short-circuited or broken, damage to each component due to overload does not occur, and if these are eliminated, the operation will return to normal and will continue for a long time. Therefore, stable operation can be obtained.

Further, since the temperature measuring signal is obtained by detecting the phase difference of only the temperature measuring element, it has the characteristic that the temperature can be controlled regardless of the dimensional accuracy of the heat sensitive layer of the temperature measuring element. Since the power to the heater is cut off when the wire is broken or short-circuited or when a major part fails, the heater does not abnormally overheat until the accident of a burnout, and the heater can be used with peace of mind.

[Brief description of drawings]

FIG. 1 is a basic 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 of a voltage applied to the temperature measuring element and a current flowing through the temperature measuring element.

FIG. 4 is a waveform diagram of a collector current of a transistor Q1.

FIG. 5 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 Thyristor 5 Detection conductor C1, C2 Capacitors Q1, Q2 Transistors D1, D2, 6, 13, 16 Diodes R, R1, R2, R3, 8, 9, 12, 14 Resistance 7 Variable resistance 10 Temperature measuring element 17, 18 Heating resistor

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[Procedure amendment]

[Submission date] July 4, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

FIG. 3 shows a voltage v applied to the temperature measuring element 10 and a waveform of a current i flowing through the temperature measuring element 10 (shown as a sine wave for convenience of explanation). The voltage v is the voltage E of the AC power source 1 as a resistance R. When the current i is a positive half-wave (between times t1 and t3) by the voltage across the resistor R1 obtained by dividing the voltage divided by the capacitor C1 by the resistors R1 and R2, the temperature measuring element 10 and the transistor Q
A base current flows to the transistor Q1 in route 1 of the base - the emitter-resistor R2, the other voltage v is negative half-wave (time ·· ~t2, t 4 ~t6 between) diode when D2
Becomes conductive and a negative half-wave of the voltage across the resistor R2 is applied to the collector of the transistor Q1.

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Claims (4)

[Claims] 1. A resistance and a first capacitor are connected in series to an AC power source, a voltage across the first capacitor is divided, and a first diode is connected in reverse polarity to the base-emitter of the first transistor in parallel with the voltage. A temperature-measuring element is connected in series to an object and one of the divided voltages is applied, and the other of the divided voltages is applied to the second diode and another resistor connected in series with the emitter-collector of the first transistor and applied to the temperature-measuring element. The phase difference between the generated AC voltage and the current flowing therein is obtained as a temperature measurement signal from the collector side of the first transistor, and this temperature measurement signal is input to the second transistor via the second capacitor,
A temperature control device characterized in that a control element is turned on / off by controlling the operation of a second transistor corresponding to charging / discharging of a capacitor to control energization to a heater. 2. The temperature control device according to claim 1, wherein the heater is deenergized by disconnection or short circuit of the temperature measuring element, and normal operation is restored by eliminating the disconnection or short circuit. 3. The temperature control device according to claim 1, wherein the heater is provided with a detection conductor through a melted layer, and the heater and the detection conductor are short-circuited to interrupt the power supply to the heater. 4. The temperature detecting device according to claim 1, wherein the heater is deenergized when the second transistor is short-circuited.