JP5708384B2 - Heater disconnection detection device, power adjustment device, and heater disconnection detection method - Google Patents

Description

  The present invention relates to a heater disconnection detection device and a heater disconnection detection method for detecting disconnection of a pure metal heater (lamp heater) whose resistance value varies greatly depending on temperature, and a power adjustment device in which the heater disconnection detection device is mounted. It is about.

For example, a conventional heater disconnection detection device that detects disconnection of a pure metal heater (lamp heater) detects a heater voltage that is a voltage applied to the heater and a heater current that is a current flowing through the heater. In addition, a method of determining the disconnection of the heater from the relationship between the heater voltage and the heater current is used (see, for example, Patent Documents 1 and 2).
However, when the type of heater is a pure metal heater or the like, the resistance value changes greatly with the temperature change of the heater. Therefore, even if the same voltage is applied to the heater, the current flowing through the heater is transiently changed. It changes a lot.

Here, FIG. 7 is an explanatory diagram showing changes in the heater current when the heater voltage is changed stepwise.
As can be seen from FIG. 7, when the heater voltage is increased stepwise, the heater current increases transiently at the time of switching the heater voltage, and then stabilizes to a constant value as time elapses.
On the other hand, when the heater voltage is lowered stepwise, the heater current greatly decreases transiently when the heater voltage is switched, and then stabilizes to a constant value as time elapses.
In this way, even if the heater voltage is the same voltage, the heater current changes with time, and thus the relationship between the heater voltage and the heater current cannot be simply determined.

Therefore, in the conventional heater disconnection detection device, the heater current is measured after a sufficient time has elapsed since the heater voltage was switched before the heater disconnection detection processing actually started and the heater current value became stable. By repeatedly performing the above process, the heater current at the time of stability corresponding to a plurality of heater voltages is collected. Then, an approximate expression indicating a correspondence relationship between a plurality of heater voltages and a stable heater current is created.
In the conventional heater disconnection detection device, when the heater disconnection detection process is started, the heater voltage and heater current are measured, and the heater voltage (hereinafter referred to as “reference heater current”) is calculated by substituting the heater voltage into the approximate expression. If the measured value of the heater current is smaller than the reference heater current, disconnection or deterioration of the heater is authorized.

In addition, in a heat treatment apparatus in which a plurality of heaters are connected in parallel, the yield of heat-treated products is affected, so there is a demand for detecting the occurrence of a situation where one of the plurality of heaters is disconnected. is there. However, it is not practical to install a voltmeter and an ammeter in each heater because the cost increases significantly and the space required for each heater also increases. For this reason, the disconnection is detected by the following method.
FIG. 8 shows a plot of the relationship between the heater voltage and the stable heater current at a plurality of points in a heat treatment apparatus in which ten heaters of the same standard are connected in parallel, and the plurality of points are connected by line segments. It is explanatory drawing which shows the relationship between the reference | standard heater current which the broken line shows, and the step-like heater voltage and heater current of FIG.
In FIG. 8, the solid line indicates the reference heater current, 105% of the reference heater current is indicated by a broken line, and 95% of the reference heater current is indicated by a one-point broken line.

FIG. 9 shows the heater current, the reference heater current, etc. when one of the 10 heaters of the same standard is disconnected and the stepped heater voltage of FIG. 7 is applied.
In FIG. 9, the solid line indicates the reference heater current, 105% of the reference heater current is indicated by a broken line, 95% of the reference heater current is indicated by a one-point broken line, and 85% of the reference heater current is indicated by a two-point broken line. .

Of the points plotted in FIG. 8, in the region where the heater voltage is high, the heater current is plotted in the vicinity of the reference heater current, but in the region where the heater voltage is low, not only in the vicinity of the reference heater current, It can be seen that the heater current is plotted over a wide range.
Also in FIG. 9, in the region where the heater voltage is high, the heater current is plotted in the vicinity of the reference heater current (near the value obtained by multiplying the reference heater current by 9/10), but in the region where the heater voltage is low, It can be seen that the heater current is plotted not only in the vicinity of the reference heater current but also in a wide range.

Therefore, calculating the reference heater current and simply comparing the measured value of the reference heater current and the heater current cannot correctly determine the disconnection or deterioration of the heater.
Therefore, only when the alarm state continues for a predetermined number of times or more, the probability of a false alarm is reduced by generating a disconnection alarm indicating that the heater is disconnected.

Japanese Patent No. 2668351 (paragraph number [0006], FIG. 1) Japanese Patent Laid-Open No. 10-48280 (paragraph number [0009], FIG. 1)

Since the conventional heater disconnection detection device is configured as described above, a false alarm is generated by generating a disconnection alarm indicating that the heater is disconnected only when the alarm state continues for a predetermined number of times. The reduction of the probability of occurrence is attempted. However, since the determination of whether or not the heater is disconnected is based solely on the result of comparison between the measured value of the heater current and the reference heater current, the heater may not be disconnected depending on the heater usage. However, the measured value of the heater current may be significantly different from the reference heater current. For example, when the heater operation is controlled when the heater voltage is relatively low, the time fluctuation of the heater current increases, and if disconnection is detected in such a situation, a heater current that is significantly different from the reference heater current is detected. As a result, there is a problem that the heater breakage cannot be accurately determined.
In addition, the amount of operation from the temperature controller constantly increases and decreases due to the effects of noise in the field, so the heater voltage and heater current also constantly increase and decrease. Difficult to set. For this reason, there has been a problem that the alarm judgment range and the alarm state cannot be appropriately set, and no alarm is generated or a false alarm is generated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. A heater disconnection detection device and a heater disconnection that can accurately determine the disconnection of the heater and can promptly generate a disconnection alarm when the disconnection occurs. The purpose is to obtain a detection method.
Another object of the present invention is to obtain a power adjustment device equipped with a heater disconnection detection device that can accurately determine the disconnection of a heater and promptly generate a disconnection alarm when the disconnection occurs. .

  The heater break detection device according to the present invention comprises a heater current measuring means for measuring a heater current that is a current flowing through the heater over a predetermined time interval or a predetermined time, and a heater voltage that is a voltage applied to the heater for a predetermined time. A heater voltage measuring means for measuring over an interval or a predetermined time, a heater current fluctuation amount measured by the heater current measuring means and a heater voltage fluctuation amount measured by the heater voltage measuring means are monitored, and the heater current and If the fluctuation amount of the heater voltage is continuously within the predetermined range, it is determined that the heater current and the heater voltage are stable, and the stability determination unit determines that the heater current and the heater voltage are stable. The heater current measured by the heater current measuring means and the heater voltage measured by the heater voltage measuring means. Based on the number of heaters, the counter corresponding to the measured heater voltage and the measured heater current is specified, and the counter specifying means for incrementing the counter value, the number of heaters Among the other counters, the counter having the maximum count value is identified, the number of heaters corresponding to the counter is estimated to be the number of heaters that are not disconnected, and the estimated number of heaters is mounted. If the number of heaters is less than the number of heaters, a heater disconnection determination unit is provided for determining that the heater is disconnected, and the alarm generation unit detects that the heater is disconnected when the heater disconnection determination unit determines that the heater is disconnected. A disconnection alarm is generated to indicate that this is occurring.

  In the heater disconnection detecting device according to the present invention, the stability determining means has a difference between the heater current measured this time by the heater current measuring means and the heater current measured last time is a predetermined value or less, and the heater voltage measuring means If the difference between the heater voltage measured this time and the heater voltage measured last time is less than or equal to a predetermined value for a predetermined number of times, it is determined that the heater current and heater voltage are stable. It is.

  In the heater break detection device according to the present invention, the counter specifying means is mounted based on the measurement results of the heater current and the heater voltage measured in advance in a state where all the mounted heaters are stably operated. An approximate expression indicating a correspondence relationship between the heater current and the heater voltage corresponding to the number of heaters that have been made is prepared, and the heater voltage measured in a state determined to be stable by the stability determination unit is approximated. Calculate the reference heater current by substituting into the formula, and calculate the stable operating current range of the heater current corresponding to the number of mounted heaters based on the reference heater current and the number of mounted heaters If the heater current measured by the heater current measuring means belongs to the current range, the counter corresponding to the number of mounted heaters is currently disconnected. The number of the heater is not is obtained so as to identify that the counter associated.

  In the heater disconnection detecting device according to the present invention, the counter specifying means, if the heater current measured by the heater current measuring means does not belong to the current range, the number of heaters less than the number of heaters mounted, Based on the reference heater current and the number of mounted heaters, a current range of the heater current in which the small number of heaters is operating stably is calculated, and the heater current measured by the heater current measuring means is calculated. Is in the current range, the counter corresponding to the small number of heaters is specified as the counter corresponding to the number of heaters that are not currently disconnected.

In the heater break detection device according to the present invention, when the counter specifying means has a reference heater current Ib, the number of mounted heaters m, and the required number of heaters n, the number n of heaters is stable. Thus, the upper limit of the current range of the heater current I (n) that is operating is calculated as I _upper (n), and the lower limit is calculated as I _under (n).
I _upper (n) = Ib × (n + 0.5) / m
I _under (n) = Ib × (n−0.5) / m

  In the heater disconnection detecting device according to the present invention, even when the number of heaters corresponding to the counter having the maximum count value is smaller than the number of heaters mounted, the heater disconnection determining means is configured to provide a counter for each number of heaters. The sum of the count values is calculated, and if the value obtained by dividing the sum of the count values by the count value incremented every power cycle is equal to or less than a predetermined value, the disconnection determination of the heater is not performed.

  In the heater disconnection detecting device according to the present invention, even when the number of heaters corresponding to the counter having the maximum count value is smaller than the number of heaters mounted, the heater disconnection determining means is configured to provide a counter for each number of heaters. The sum of the count values is calculated, and if the ratio of the maximum count value to the sum of the count values is equal to or less than a predetermined value, the heater disconnection determination is not performed.

  In the heater disconnection detection device according to the present invention, when the number of heaters corresponding to the counter having the maximum count value is smaller than the number of heaters mounted, the heater disconnection determination means includes a counter for each number of heaters. Thus, it is determined that the heater is disconnected on the condition that the counter having the maximum count value is the same continuously for a predetermined number of times.

  In the heater disconnection detection device according to the present invention, when the heater disconnection determination means determines that the heater is disconnected, the number of heaters corresponding to the counter having the maximum count value and the number of heaters mounted are calculated. The difference is output, and the alarm generation means outputs the difference output from the heater disconnection determination means as a disconnection alarm.

  The power adjustment device according to the present invention includes a power regulator that controls the current flowing through the heater in accordance with the operation amount of the temperature regulator, and is mounted with any of the heater disconnection detection devices described above.

  The heater disconnection detection method according to the present invention includes a heater current measurement processing step in which the heater current measurement means measures a heater current, which is a current flowing through the heater, over a predetermined time interval or a predetermined time, and the heater voltage measurement means applies to the heater. A heater voltage measurement processing step for measuring the heater voltage, which is a current voltage, over a predetermined time interval or over a predetermined time, a fluctuation amount of the heater current measured by the stability determination means in the heater current measurement processing step, and the heater voltage measurement processing The amount of change in the heater voltage measured in the step is monitored, and if the amount of change in the heater current and the heater voltage is continuously within a predetermined range, it is determined that the heater current and the heater voltage are stable. The stability determination processing step and the stability determination processing step. Based on the heater current measured in the heater current measurement processing step and the heater voltage measured in the heater voltage measurement processing step, the specifying means determines the measured heater voltage and the A counter identification processing step for identifying a counter corresponding to the measured heater current and incrementing the count value of the counter, and a heater disconnection determination means, select the counter with the maximum count value among the counters by number of heaters. If the number of heaters corresponding to the counter is estimated to be the number of heaters that are not disconnected, and the estimated number of heaters is less than the number of heaters that are mounted, the heater is disconnected The heater disconnection determination processing step to be determined and the heater disconnection determination processing step determine whether the heater has been disconnected. If the alarm generating means, in which and a warning generating process step of generating a break alarm indicating that the heater is disconnected.

  According to the present invention, there is an effect that the disconnection of the heater can be accurately determined and a disconnection alarm can be promptly generated when the disconnection occurs.

It is a block diagram which shows the electric power adjustment apparatus which mounts the heater disconnection detection apparatus by Embodiment 1 of this invention. It is a flowchart which shows the processing content of the heater disconnection detection apparatus by Embodiment 1 of this invention. When the number of heaters is 20, it is explanatory drawing which shows the correspondence of the heater current and heater voltage which were measured when it was judged that it was stable in the stability judgment part 23. FIG. FIG. 4 is an enlarged view in which a part of FIG. 3 is enlarged. It is explanatory drawing which shows the heater current and heater voltage (experimental result) measured when creating an approximate expression, the approximate expression created from the heater current and heater voltage, and the like. It is explanatory drawing which shows an example of the electric current range of the heater electric current according to the number of heaters. It is explanatory drawing which shows the change of a heater current at the time of changing a heater voltage in steps. In a heat treatment apparatus in which 10 heaters of the same standard (zero disconnected heaters) are connected in parallel, the relationship between the heater voltage and the heater current at the time of stability is plotted at a plurality of points. FIG. 8 is an explanatory diagram showing a relationship between a reference heater current indicated by a broken line connected by a line segment, a step-like heater voltage and a heater current in FIG. 7. In a heat treatment apparatus in which 10 heaters of the same standard (one heater is disconnected) are connected in parallel, the relationship between the heater voltage and the stable heater current is plotted at a plurality of points. It is explanatory drawing which shows the relationship between the reference | standard heater current which the broken line connected by the minute shows, and the step-like heater voltage and heater current of FIG.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing a power adjustment device in which a heater disconnection detection device according to Embodiment 1 of the present invention is mounted.
In FIG. 1, the temperature controller 1 collects the measured values of the temperature sensor installed in the vicinity of the heater 4 (the temperature in the vicinity of the heater 4), and sets the operation amount for matching the measured value of the temperature sensor with the temperature setting value. A process of outputting to the power adjustment device 2 is performed.
The power adjustment device 2 performs a process of controlling the heater current I that is a current flowing from the AC power source 3 to the heater 4 based on the operation amount output from the temperature regulator 1.
In addition, the power adjustment device 2 is equipped with a heater disconnection detection device 5 that detects the disconnection of the heater 4. When the heater disconnection detection device 5 detects the disconnection of the heater 4, the disconnection indicating that the heater 4 is disconnected. Implement a process that generates an alarm.

In FIG. 1, the internal circuit of the heater 4 is not shown, but it is assumed that N (N is an integer of 1 or more) heaters having the same rating are connected in parallel.
The heater 4 is a member that generates heat when a current flows and heats a temperature control object.
However, the type of the heater is not particularly limited, and for example, a heater having strong nonlinear characteristics such as a lamp heater, a ceramic heater, or a pure metal heater is applicable.
The heater disconnection detection device 5 performs a disconnection detection process for the heater 4 and, if any heater in the heater 4 is disconnected, performs a process for generating a disconnection alarm indicating that the heater is disconnected. .

The power regulator 11 performs a process of outputting a switching signal corresponding to the operation amount output from the temperature regulator 1 to the switch 12. The open / close signal includes a signal that is only an open signal and not a close signal, such as an ignition signal to a thyristor.
The switch 12 is composed of, for example, a thyristor and acts as a switch that conducts current in accordance with an opening / closing signal output from the power regulator 11.
The current detector 13 is composed of a current transformer, for example, and detects a heater current I that is a current flowing through the heater 4.

For example, the heater current measuring unit 21 collects the detection results of the current detector 13 and measures the heater current I for each power cycle of the AC power supply 3. The heater current measuring unit 21 constitutes heater current measuring means.
The heater voltage measurement unit 22 measures the heater voltage V, which is a voltage applied to the heater 4, by detecting a voltage difference applied to both ends of the heater 4, for example, every power cycle of the AC power supply 3. To implement. The heater voltage measuring unit 22 constitutes a heater voltage measuring unit.

The stability determination unit 23 is composed of, for example, a semiconductor integrated circuit on which a CPU is mounted, a one-chip microcomputer, or the like. The fluctuation amount ΔI of the heater current I measured by the heater current measurement unit 21 and the heater voltage measurement unit 22 is monitored, and if the heater current I and the heater voltage V fluctuation amounts ΔI and ΔV continue to fall within a predetermined range, the heater current I and the heater voltage I are measured. A process of determining that the voltage V is stable is performed.
That is, the stability determination unit 23 has a difference ΔI between the heater current I _j measured this time by the heater current measurement unit 21 and the heater current I _j−1 measured last time is equal to or less than a predetermined threshold ΔI _th (predetermined value). In addition, the difference ΔV between the heater voltage V _j measured this time by the heater voltage measuring unit 22 and the heater voltage V _j−1 measured last time is continuously equal to or less than a predetermined threshold ΔV _th (predetermined value) for a predetermined number of times C. If so, it is determined that the heater current I and the heater voltage V are stable.
The stability determination unit 23 constitutes a stability determination unit.

  The counter specifying unit 24 is composed of, for example, a semiconductor integrated circuit mounted with a CPU or a one-chip microcomputer, and the stability determination unit 23 determines that the heater current I and the heater voltage V are stable. In this case, based on the heater current I measured by the heater current measuring unit 21 and the heater voltage V measured by the heater voltage measuring unit 22, the heater voltage V and the heater current I are determined in the counter for each number of heaters. A corresponding counter is specified, and a process of incrementing the count value k of the counter is performed. The counter specifying unit 24 constitutes a counter specifying unit.

The counter for each number of heaters is mounted in the heater count storage unit 25 (when the heater 4 is connected in parallel with N heaters, N counters are mounted).
The count value k of the counter for each number is 0 in the initial stage. For example, when it can be determined that there is a high possibility that the number Bc of heaters that are not currently disconnected is nine, the count of the counter corresponding to nine is counted. The value k is incremented (how to determine will be described later).
The counter only needs to be capable of incrementing the count value under the instruction of the counter specifying unit 24. For example, the counter may be composed of an electronic circuit or a memory such as a buffer. It may be what you have.

The determination cycle management unit 26 includes, for example, a cycle counter. The cycle management unit 26 manages the cycle for executing the heater disconnection detection process. When the timing for executing the heater disconnection detection process is reached, a detection execution command is sent to the heater disconnection determination unit 27. Execute the process to output to.
The heater disconnection determination unit 27 is constituted by, for example, a semiconductor integrated circuit on which a CPU is mounted, a one-chip microcomputer, or the like. When a detection execution command is received from the determination cycle management unit 26, the heater number count storage unit 25 Among the counters according to the number of heaters mounted, the counter C _max having the maximum count value k is specified, and the number n of heaters corresponding to the counter C _max is estimated to be the number of heaters that are not disconnected. Then, when the estimated number of heaters is smaller than the number m of heaters mounted, processing for determining that the heater is disconnected is performed.
The determination cycle management unit 26 and the heater disconnection determination unit 27 constitute a heater disconnection determination unit.

  For example, the alarm generation unit 28 includes a display on which an output relay, an LED lamp, or the like is mounted, a speaker that outputs sound or alarm sound, and the heater disconnection determination unit 27 determines that the heater is disconnected. In addition, a process for generating a disconnection alarm indicating that the heater is disconnected is performed.

In the example of FIG. 1, the heater current measurement unit 21, the heater voltage measurement unit 22, the stability determination unit 23, the counter identification unit 24, the count storage unit 25 by number of heaters, and the determination cycle management unit, which are components of the heater disconnection detection device 26, the heater disconnection determination unit 27 and the alarm generation unit 28 are assumed to be configured by dedicated hardware, but the heater disconnection detection device may be configured by a computer.
When the heater disconnection detection device is configured by a computer, the heater current measurement unit 21, the heater voltage measurement unit 22, the stability determination unit 23, the counter identification unit 24, the count storage unit 25 by number of heaters, the determination cycle management unit 26, What is necessary is just to store the program which describes the processing content of the heater disconnection determination part 27 and the alarm generation part 28 in the memory of a computer, and to run the program stored in the memory of the said computer.
FIG. 2 is a flowchart showing the processing contents of the heater break detection device according to Embodiment 1 of the present invention.

Next, the operation will be described.
Before the heater disconnection detection device starts the heater disconnection detection process, an approximate expression indicating the correspondence relationship between the heater current and the heater voltage corresponding to the number of heaters mounted is created.
This approximate expression is created based on the heater current and the heater voltage measured with all the mounted heaters operating stably. As described above, the heater current is the heater voltage. If it is changed stepwise, it changes greatly when the heater voltage is switched, and there is a characteristic that stabilizes to a constant value with the passage of time. The heater current and the heater voltage measured in the state are used.

Here, FIG. 3 is an explanatory diagram showing the correspondence between the heater current and the heater voltage measured when the stability determination unit 23 determines that the number of heaters is 20, and the stability determination unit 23 determines that the heaters are stable.
FIG. 4 is an enlarged view of a part of FIG.
In FIG. 3 and FIG. 4, many points indicating the measured values of the heater current and the heater voltage are plotted, and the positions of the plotted points are influenced by the effect that the resistance value of the heater changes with the temperature change. Although there is some variation, it is generally located near one line.
In the first embodiment, the heater current on one line is referred to as “reference heater current”, and the range of reference heater current × 1.025 to reference heater current × 0.975 is defined as a stable operation range.
Therefore, although details will be described later, when the state where the heater current I measured by the heater current measuring unit 21 deviates from the stable operation range exceeds a predetermined ratio, it is determined that the heater is disconnected.
For example, the current range when the heater current I measured by the heater current measuring unit 21 deviates from the stable operation range and one heater is disconnected (reference heater current × 0.975 to reference heater current × If the state within the range (0.925) exceeds a predetermined ratio, it is determined that one heater is disconnected.

In the first embodiment, an approximate expression indicating the correspondence relationship between the reference heater current and the heater voltage on one line is created.
FIG. 5 is an explanatory diagram showing the heater current and heater voltage (experimental results) measured when creating the approximate expression, and the approximate expression created from the heater current and heater voltage.

Hereinafter, the heater disconnection detection processing by the heater disconnection detection device 5 will be specifically described with reference to FIG.
The temperature controller 1 collects the measured value of the temperature sensor installed in the vicinity of the heater 4 (the temperature in the vicinity of the heater 4), and sets the operation amount to match the measured value of the temperature sensor with the temperature setting value. Output to 2.
For example, if the measured value of the temperature sensor is lower than the temperature set value, an operation amount corresponding to a control signal for raising the temperature is output to the power adjustment device 2, and if the measured value of the temperature sensor is higher than the temperature set value, the temperature The operation amount corresponding to the control signal for lowering is output to the power adjustment device 2. If the measured value of the temperature sensor matches the temperature set value, an operation amount corresponding to a control signal for maintaining the temperature is output to the power adjustment device 2.

When starting the heater disconnection detection process, the counter specifying unit 24 of the heater disconnection detection device 5 initializes the count value k of the counter for each number of heaters mounted in the count storage unit 25 for each heater to 0. (Step ST1).
Further, the stability determination unit 23 initializes the count value Cs of the stability determination counter to 0 (step ST1).
In addition, the determination cycle management unit 26 initializes the count value Cd of the cycle counter to 0 as a cycle for executing the heater disconnection detection process (step ST1).

The heater disconnection detection device 5 executes the subsequent process when the measurement cycle (measurement timing) is reached, and waits for the subsequent process to be executed until the next measurement cycle when the subsequent process ends.
The “measurement period” is, for example, a period that is a natural number multiple of the half cycle period of the power supply, and the timing for executing the subsequent processing is the timing at which the power supply voltage becomes 0 V (zero cross point).

For example, the heater current measuring unit 21 of the heater disconnection detecting device 5 collects the detection results of the current detector 13 for each power cycle of the AC power supply 3 and measures the heater current I, and the measured value of the heater current I is obtained. It outputs to the stability discrimination | determination part 23 (step ST3).
The heater voltage measurement unit 22 measures the heater voltage V, which is the voltage applied to the heater 4, by measuring the voltage difference applied to both ends of the heater 4 for each power cycle of the AC power supply 3, for example. Then, the measured value of the heater voltage V is output to the stability determination unit 23 (step ST4).

When the stability determination unit 23 receives the measurement value of the heater current I from the heater current measurement unit 21 and the measurement value of the heater voltage V from the heater voltage measurement unit 22, the fluctuation amount ΔI of the heater current I and the heater voltage V The fluctuation amount ΔV of the heater current I and the heater voltage V is monitored to determine whether the fluctuation amounts ΔI, ΔV of the heater current I and the heater voltage V are continuously within a predetermined range. It is determined whether or not is stable.
Specifically, it is determined whether the heater current I and the heater voltage V are stable as follows.

Stability determination unit 23 calculates the difference ΔI between the heater current I _j measured this time by the heater current measuring unit 21, and the heater current I _j-1 that was measured last time (step ST5).
ΔI = | I _j −I _j−1 | (1)
However, I _j is the heater current measured in the jth power cycle, and I _j−1 is the heater current measured in the j−1 power cycle.

Further, the stability discriminator 23 calculates the difference ΔV of the heater voltage V _j measured this time by the heater voltage measuring unit 22, the heater voltage V _j-1 that was measured last time (step ST5).
ΔV = | V _j −V _j−1 | (2)
Where V _j is the heater voltage measured in the jth power cycle, and V _j−1 is the heater voltage measured in the j−1 power cycle.

When the stability determination unit 23 calculates the difference ΔI indicating the fluctuation amount of the heater current I and the difference ΔV indicating the fluctuation amount of the heater voltage V, the difference ΔI indicating the fluctuation amount of the heater current I and a predetermined threshold value ΔI _th. And a difference ΔV indicating the amount of fluctuation of the heater voltage V and a predetermined threshold value ΔV _th are compared.
If the difference ΔI is equal to or less than the threshold value ΔI _th and the difference ΔV is equal to or less than the threshold value ΔV _th (step ST6), the stability determination unit 23 may have a stable heater current I and heater voltage V. Therefore, the count value Cs of the stability determination counter is incremented (step ST7).
When the difference ΔI is larger than the threshold value ΔI _th or when the difference ΔV is larger than the threshold value ΔV _th (step ST6), the stability determination unit 23 does not stabilize the heater current I and the heater voltage V and is unstable. Therefore, the count value Cs of the stability determination counter is cleared and the count value Cs is returned to 0 (step ST8).

  The stability determination unit 23 compares the count value Cs of the stability determination counter with the predetermined value C, and if the count value Cs of the stability determination counter has reached the predetermined value C (step ST9), the difference ΔI and the difference Since ΔV is continuously below the threshold value C times and the heater current I and the heater voltage V are likely to be stable, it is determined that the heater current I and the heater voltage V are stable (step ST10). .

The counter specifying unit 24 measures the heater current I measured by the heater current measuring unit 21 and the heater voltage measuring unit 22 when the stability determining unit 23 determines that the heater current I and the heater voltage V are stable. Based on the heater voltage V, the counter corresponding to the heater voltage V and the heater current I (the number of heaters Bc that are not currently disconnected) is specified among the counters by number of heaters (step ST11).
Specifically, the counter corresponding to the number Bc of heaters that are not currently disconnected is specified as follows.

First, the counter specifying unit 24 measures the approximate expression (approximate expression corresponding to the number of mounted heaters) created before starting the disconnection detection process of the heater 4 by the heater voltage measuring unit 22. The reference heater current Ib is calculated by substituting the heater voltage V (for example, the heater voltage measured in a stable state before starting the disconnection detection process of the heater 4).
The reference heater current Ib is a heater current on one line located at the center of the stable operation range shown in FIGS.
When the counter specifying unit 24 calculates the reference heater current Ib, for example, as shown in the following formula (3), the reference heater current Ib and the number m of heaters mounted (in the heater 4 are connected in parallel). Current heater), and the current range of the heater current I (n) corresponding to the case where n heaters are operating stably.

I _upper (n) = Ib × (n + 0.5) / m
I _under (n) = Ib × (n−0.5) / m (3)
However, I _upper (n) is the current range of the heater current I (n) in which the required number n of heaters is operating stably (when n = m, the number m of heaters mounted is stable. The upper limit of the operating heater current I (n = m) current range) is indicated, and I _under (n) is the lower limit.
For example, if Ib = 10A, m = 20, and n = 20, the current range of the heater current I (n = m = 20) corresponding to the number m of heaters mounted is as follows: .
I _upper (n = 20) = 10 × (20 + 0.5) /20=10.25A
I _under (n = 20) = 10 × (20−0.5) /20=9.75A

When the counter specifying unit 24 calculates the current range corresponding to the number m of heaters mounted, the counter specifying unit 24 determines whether or not the heater current I measured by the heater current measuring unit 21 belongs to the calculated current range. To do.
For example, when the current range of the heater current I (n = m) corresponding to the number m of mounted heaters is 9.75 A to 10.25 A, the heater current I measured by the heater current measuring unit 21 is 9 .88 A, it is determined that the heater current I belongs to the current range. However, if the heater current I measured by the heater current measuring unit 21 is 9.62 A, the heater current I is the current. It is determined that it does not belong to the range.

  If the counter specifying unit 24 determines that the heater current I measured by the heater current measuring unit 21 belongs to the calculated current range, the counter corresponding to the number m of the mounted heaters is currently disconnected. It is specified that the counter corresponds to the number Bc (that is, Bc = m) of heaters that are not used.

If the counter specifying unit 24 determines that the heater current I measured by the heater current measuring unit 21 does not belong to the calculated current range, as shown in the above equation (3), From the number m of heaters mounted and the number n of heaters that are not disconnected less than the number m of mounted heaters (n <m), the number n of heaters that are not disconnected is stable. A current range of the heater current I (n (n <m)) when operating is newly calculated.
For example, if Ib = 10 A, m = 20, and n = 19, the current range in which n = 19 heaters are operating stably can be calculated using the above equation (3) as follows: Is calculated.
I _upper (n = 19) = 10 × (19 + 0.5) /20=9.75A
I _under (n = 19) = 10 × (19−0.5) /20=9.25A

Here, FIG. 6 is an explanatory diagram showing an example of a current range of the heater current I for each number of heaters.
In the example of FIG. 6, the current range of the heater current I when the number of the heaters that are stably operating is 10 out of the 10 heaters that are mounted, is operating stably. The current range of the heater current I when the number of heaters is nine, ..., the current range of the heater current I when the number of heaters operating stably is one, respectively. FIG. 6 shows the current range in which the number n of heaters operating stably is 0 to 10, but in the present embodiment, 10 installed heaters operate stably. If the current range of the heater is not included in this current range, the current range of the number that is less than the number that is mounted, It asks sequentially as needed. This is preferable in that the number of points (data) to be set can be suppressed. If there is a margin in the capacity of the memory or the like, a plurality or all current ranges may be obtained.

When the counter specifying unit 24 calculates a stable operating current range corresponding to the number n (for example, n = m−1) of heaters that are not disconnected less than the number m, the heater current I measured by the heater current measuring unit 21 is calculated. Determines whether it belongs to the calculated current range.
For example, when the stable operating current range of the heater current when Ib = 10 A, m = 20, and n = 19 is 9.25 A to 9.75 A, the heater current I measured by the heater current measuring unit 21 is If it is 9.50 A, it is determined that the heater current I belongs to the current range, but if the heater current I measured by the heater current measuring unit 21 is 9.11 A, the heater current I is It is determined that it does not belong to the current range.

When the counter specifying unit 24 determines that the heater current I measured by the heater current measuring unit 21 belongs to the current range, the counter corresponding to the number n of heaters that are not disconnected is smaller than the number m. It is specified that the counter corresponds to the number Bc of heaters that are not currently disconnected.
For example, if the number n of heaters that are not disconnected is m−1, the counter corresponding to m−1 is identified as the counter corresponding to the number Bc of heaters that are not currently disconnected.

If the counter specifying unit 24 determines that the heater current I measured by the heater current measuring unit 21 does not belong to the previously calculated current range, the counter specifying unit 24 and the number m of heaters mounted are calculated. From the number n of heaters that are not disconnected (for example, n = m−2), which is smaller than the number of heaters that have been previously determined (for example, m−1), this number n = m−2 heaters. Further calculates the current range of the heater current I (n = m−2) in which the heater is operating stably, and determines whether or not the heater current I measured by the heater current measuring unit 21 belongs to this current range. As a result, the counter corresponding to the number Bc of heaters that are not currently disconnected is specified.
That is, the counter specifying unit 24 counts the number n of undisconnected heaters less than the number m until the heater current I measured by the heater current measuring unit 21 falls within the stable operating current range of the heater current I (n) calculated. The calculation of the current range of the heater current I (n) corresponding to the number n is repeated. Then, the counter corresponding to the number n of stable operating current ranges to which the heater current I belongs is specified as the counter corresponding to the number Bc of heaters that are not currently disconnected. In the present embodiment, the stable current range is calculated while reducing the number n of heaters one by one, but the number of heaters may be changed as necessary.

When the counter specifying unit 24 specifies a counter corresponding to the number Bc of heaters that are not currently disconnected, the counter specifying unit 24 corresponds to the number Bc among the counters by number of heaters mounted by the heater count storage unit 25. The count value k of the counter is incremented (step ST12).
For example, if the number Bc of heaters that are not currently disconnected is 10, the count value k of the counter corresponding to 10 is incremented, and if the number Bc of heaters that are not currently disconnected is 9, then 9 The count value k of the counter corresponding to is incremented.

When the counter specifying unit 24 increments the count value k of the counter corresponding to the number Bc, the determination cycle management unit 26 determines that the heater current I and the heater voltage V are not stable by the stability determination unit 23. If the count value Cs of the stability determination counter does not reach the predetermined value C, the count value Cd of the cycle counter is incremented (step ST13).
At this time, if the count value Cd of the cycle counter does not satisfy the predetermined value D indicating the cycle for performing the heater disconnection detection process, the process returns to step ST2, and the processes of steps ST3 to ST13 are repeatedly performed (step ST14). ).

When the count value Cd of the cycle counter reaches a predetermined value D indicating the cycle of executing the heater disconnection detection process, the determination cycle management unit 26 determines that it is time to execute the heater disconnection detection process, and executes a detection execution command. Is output to the heater disconnection determination unit 27.
When the heater disconnection determination unit 27 receives a detection execution command from the determination cycle management unit 26, the counter C having the maximum count value k among the counters by the number of heaters mounted by the heater count storage unit 25. _{Specify max} .

Among the counters according to the number of heaters, the number n of heaters corresponding to the counter C _max with the maximum count value k is likely to indicate the number of heaters that are not disconnected. When the ratio at which the heater current I and the heater voltage V are determined to be stable by the determination unit 23 is small (for example, when the change of the set temperature is repeated in a short time, it is stable). However, the reliability of the heater disconnection detection process is reduced, so it may be considered that it is better not to generate a disconnection alarm.

Therefore, the heater disconnection determination unit 27 calculates the total C _total of the counter values for each number of heaters, and uses the total C _total of the count values as the count value Cd of the cycle counter (the AC power source 3 of the predetermined period). Then, it is determined whether or not the division value (= C _total / Cd) is equal to or less than a predetermined value R (step ST15).
When the division value (= C _total / Cd) is equal to or less than the predetermined value R, the heater disconnection determination unit 27 detects the heater disconnection without generating a disconnection alarm because the reliability of the heater disconnection detection process is low. The alarm generation unit 28 is instructed to generate an indeterminable alarm indicating that the determination is impossible.
As a result, the alarm generation unit 28 generates an indeterminate alarm indicating that the heater disconnection cannot be detected (step ST16).

If the divided value (= C _total / Cd) exceeds the predetermined value R, the heater disconnection determination unit 27 determines that the number n of heaters corresponding to the counter C _max with the previously specified count value k is the current value. Assuming that the number of heaters is not disconnected (step ST17), the number n of heaters corresponding to the counter _Cmax having the maximum count value k is compared with the number m of heaters mounted.
If the number n of heaters corresponding to the counter C _max having the maximum count value k is equal to the number m of heaters mounted (step ST18), the heater disconnection determination unit 27 has no heater currently disconnected. Therefore, the disconnection alarm is not generated.
If the number n of heaters corresponding to the counter C _max having the maximum count value k is smaller than the number m of heaters mounted (step ST18), it is determined that the heater is disconnected, and the heater is disconnected. The alarm generation unit 28 is instructed to generate a disconnection alarm indicating that the alarm is present.
Thereby, the alarm generation unit 28 generates a disconnection alarm indicating that the heater is disconnected (step ST19).

As apparent from the above, according to the first embodiment, the fluctuation amount ΔI of the heater current I measured by the heater current measurement unit 21 and the fluctuation amount ΔV of the heater voltage V measured by the heater voltage measurement unit 22 are calculated. A stability determination unit that monitors and determines that the heater current I and the heater voltage V are stable if the fluctuation amounts ΔI and ΔV of the heater current I and the heater voltage V are continuously within a predetermined range. If the heater 23 is determined to be stable by the heater 23 and the stability determiner 23, the heater current I measured by the heater current measuring unit 21 and the heater voltage V measured by the heater voltage measuring unit 22 are used. A counter specifying unit 24 that specifies a counter corresponding to the heater voltage V and the heater current I among the counters by number, and increments the count value k of the counter; Among the number-specific counters over data, the count value k is to identify the maximum counter C _max, estimated to be the number of heaters not disconnected the number n of the heater corresponding to the counter C _max, the When the estimated number of heaters is smaller than the number m of heaters mounted, a heater disconnection determination unit 27 that determines that the heater is disconnected is provided, and the alarm generation unit 28 uses the heater disconnection determination unit 27 to When a disconnection is detected, a disconnection alarm is generated to indicate that the heater is disconnected. Therefore, the disconnection of the heater is accurately determined, and when a disconnection occurs, a disconnection alarm is promptly generated. The effect which can be done is produced.

That is, according to the first embodiment, the stability determination unit 23 determines that the difference ΔI between the heater current I _j measured this time by the heater current measurement unit 21 and the heater current I _j−1 measured last time is a predetermined threshold value. [Delta] I _th or less, and a predetermined number of times that this measured heater voltage V _j and the heater voltage V _j-1 of the difference [Delta] V, which is previously measured by the heater voltage measuring unit 22 is equal to or smaller than a predetermined threshold value [Delta] V _th C Since the heater current I and the heater voltage V are determined to be stable if they are continuous, the heater current I and the heater voltage V measured in an unstable state are excluded, and the heater is disconnected. Can be discriminated, and there is an effect of reducing the probability of erroneous detection of heater disconnection.

Further, according to the first embodiment, the counter identification unit 24 substitutes the heater voltage V measured in a state determined to be stable by the stability determination unit 23 into the approximate expression, and the reference heater current Ib. And the current range of the heater current I corresponding to the number n of undisconnected heaters is calculated based on the reference heater current Ib, the number m of heaters mounted, and the number n of heaters not disconnected. When the state where the heater current I calculated and measured by the heater current measuring unit 21 belongs to the current range exceeds a predetermined ratio, the counter corresponding to the number n of heaters that are not disconnected is currently disconnected. Since it is configured to identify the counter corresponding to the number Bc of heaters that are not present, it is possible to increase the accuracy of identifying the counter corresponding to the number Bc of heaters that are not currently disconnected. Achieve the kill effect.
That is, in the prior art, the disconnection determination based on the relationship between the voltage and current at a certain point in time has determined the disconnection of the heater from “predetermined number of times”. Based on the totaled result, the heater disconnection is determined based on the non-disconnection determination and the disconnection determination “more / less”. According to the first embodiment, when the heater current measurement value is different from the reference heater current sporadically depending on the usage state of the heater (that is, when the heater is not disconnected but is not operating stably). ), It is possible to perform a stable heater disconnection determination process while avoiding erroneous determination.

Furthermore, according to the first embodiment, even when the number n of heaters corresponding to the counter C _max having the maximum count value k is smaller than the number m of heaters mounted, the heater disconnection determination unit 27 can The total C _total of the count values of the counters for each number of _lines is calculated, and the total C _total of the count values is divided by the count value Cd of the period counter (corresponding to the number of power cycles of the AC power supply 3 during a predetermined period) If the division value (= C _total / Cd) is equal to or less than the predetermined value R, the heater disconnection judgment is not performed, so that a disconnection alarm is generated when the reliability of the heater disconnection detection process is low. There is an effect that can be avoided.
Also, at this time, by generating an indeterminate alarm indicating that the heater disconnection detection is impossible, the heater disconnection is generated even if the disconnection alarm is not generated because the reliability of the heater disconnection detection process is low. There is also an effect that the user can be notified that there is a possibility of being.
According to the first embodiment, since the possibility of erroneous detection of heater disconnection is drastically reduced, the number of heaters connected in parallel can be increased as compared to the conventional heater disconnection detection device. Become.

Embodiment 2. FIG.
In the first embodiment, if the division value (= C _total / Cd) exceeds the predetermined value R, the number n of heaters corresponding to the counter C _max having the maximum count value k is equal to the number of heaters mounted. When the number is less than the number m, the alarm indicating that the heater is disconnected is shown. However, if there is no significant difference between the counter values k of the number of heaters, the measured value is Plotted over a wide area and considered to have low statistical reliability.
Therefore, in the second embodiment, if there is no significant difference between the count values k of the counters according to the number of heaters, a disconnection alarm is not generated and a determination indicating that the heater disconnection detection is impossible. An inability alarm is generated.
Specifically, it is as follows.

First, when the heater disconnection determination unit 27 receives a detection execution command from the determination cycle management unit 26, as in the first embodiment, the heater count counter of the number of heaters mounted by the heater count count unit 25 is set. Among them, the counter C _max having the maximum count value k is specified.
Further, the heater disconnection determination unit 27 calculates the total C _total of the count values k of the counters for each number of heaters, as in the first embodiment.

Heater disconnection determination unit 27, calculating the sum _{C total} of the count values, and calculates the ratio _{k / C total} count value k of the maximum of the counter _{C max} to the total _{C total} of the count values.
The heater disconnection determination unit 27 is considered that if the ratio k / C _total is higher than the predetermined value, the estimation result of the counter specifying unit 24 is not dispersed and the statistical reliability is considered high. If the number n of heaters corresponding to the counter C _max is less than the number m of heaters mounted, the alarm generation unit 28 is instructed to generate a disconnection alarm indicating that the heater is disconnected.
On the other hand, if the ratio k / C _{total is} less than a predetermined value, the estimated result of the counter specifying unit 24 are dispersed, it is considered to be less statistical reliability, the count value k is the maximum of the counter C _max Even when the number n of the corresponding heaters is smaller than the number m of the heaters mounted, determination that the heater disconnection detection is impossible without generating a disconnection alarm indicating that the heater is disconnected The alarm generation unit 28 is instructed to generate an impossible alarm.

As apparent from the above, according to the second embodiment, even when the number n of heaters corresponding to the counter C _max having the maximum count value k is smaller than the number m of heaters mounted, the number of heaters The sum C _total of the count values of another counter is calculated, and if the ratio k / C _total of the count value k of the maximum counter C _{max with} respect to the sum C _total of the count values is equal to or less than a predetermined value, the heater is disconnected. Therefore, it is possible to avoid the occurrence of the disconnection alarm in the state where the reliability of the heater disconnection detection process is low.
Also, at this time, by generating an indeterminate alarm indicating that the heater disconnection detection is impossible, the heater disconnection is generated even if the disconnection alarm is not generated because the reliability of the heater disconnection detection process is low. There is also an effect that the user can be notified that there is a possibility of being.

Embodiment 3 FIG.
In the first and second embodiments, when the number n of heaters corresponding to the counter C _max having the maximum count value k is smaller than the number m of heaters mounted, a disconnection alarm indicating that the heater is disconnected. However, the counter _Cmax having the largest count value k is the same for a predetermined number of times (for example, 3 times and 5 times) continuously. The heater disconnection determination unit 27 may determine that the heater is disconnected, and the alarm generation unit 28 may generate a disconnection alarm indicating that the heater is disconnected.
In this case, for example, if the predetermined number of times is N, the counter C _max having the maximum count value k needs to be the same counter during the cycle of executing the heater disconnection detection process × N. Although it takes a long time from the occurrence of the alarm to the generation of the alarm, the heater disconnection detection accuracy can be improved.

Embodiment 4 FIG.
In the first to third embodiments, when the number n of heaters corresponding to the counter C _max having the maximum count value k is smaller than the number m of heaters mounted, a disconnection alarm indicating that the heater is disconnected. However, if the heater disconnection determination unit 27 determines that the heater is disconnected, the number n of heaters corresponding to the counter C _max having the maximum count value k and the heaters mounted are determined. The difference (mn) from the number m may be output to the alarm generation unit 28, and the alarm generation unit 28 may output the difference output from the heater disconnection determination unit 27 as a disconnection alarm.
Since this difference corresponds to the number of disconnected heaters, the user can recognize not only the fact that the heater is disconnected, but also the number of disconnected heaters. .

  DESCRIPTION OF SYMBOLS 1 Temperature controller, 2 Power adjustment apparatus, 3 AC power supply, 4 Heater, 5 Heater disconnection detection apparatus, 11 Power regulator, 12 Switch, 13 Current detector, 21 Heater current measurement part (heater current measurement means), 22 Heater voltage measurement unit (heater voltage measurement unit), 23 Stability determination unit (stability determination unit), 24 Counter identification unit (heater number estimation unit), 25 Count storage unit by number of heaters, 26 Determination cycle management unit (heater disconnection determination) Means), 27 heater breakage determination part (heater breakage judgment means), 28 alarm generation part (alarm generation means).

Claims (11)

Heater current measuring means for measuring a heater current, which is a current flowing through the heater, over a predetermined time interval or over a predetermined time;
Heater voltage measuring means for measuring a heater voltage, which is a voltage applied to the heater, over a predetermined time interval or over a predetermined time;
The heater current fluctuation amount measured by the heater current measurement means and the heater voltage fluctuation amount measured by the heater voltage measurement means are monitored, and the heater current and the heater voltage fluctuation amount continue to be predetermined. Stability determination means for determining that the heater current and the heater voltage are stable if within a range;
If it is determined by the stability determination means that the number of heaters is different based on the heater current measured by the heater current measurement means and the heater voltage measured by the heater voltage measurement means. A counter specifying means for specifying a counter corresponding to the measured heater voltage and the measured heater current and incrementing a count value of the counter;
Among the counters according to the number of heaters, the counter having the largest count value is specified, the number of heaters corresponding to the counter is estimated to be the number of heaters that are not disconnected, and the estimated number of heaters is A heater disconnection judging means for judging that the heater is disconnected when the number of mounted heaters is less than the number of heaters;
A heater disconnection detection device comprising: an alarm generation means for generating a disconnection alarm indicating that the heater is disconnected when the heater disconnection determination means determines that the heater is disconnected.   The stability determining means has a difference between the heater current measured by the heater current measuring means and the heater current measured last time being equal to or less than a predetermined value, and the heater voltage measured by the heater voltage measuring means and the previous time. The heater break according to claim 1, wherein the heater current and the heater voltage are determined to be stable when the difference between the measured heater voltages is continuously a predetermined number of times or less. Detection device. The counter specifying means includes
Correspondence between heater current and heater voltage corresponding to the number of heaters mounted, based on the measurement results of heater current and heater voltage measured in advance with all mounted heaters operating stably Create an approximate expression to show the relationship,
The heater voltage measured in a state determined to be stable by the stability determination means is substituted into the approximate expression to calculate a reference heater current, and the reference heater current and the number of mounted heaters Based on the above, calculate the current range of the heater current corresponding to the number of heaters mounted,
If the heater current measured by the heater current measuring means belongs to the current range, the counter corresponding to the number of mounted heaters is identified as the counter corresponding to the number of heaters that are not currently disconnected. The heater break detection device according to claim 1 or 2, wherein The counter specifying means includes
If the heater current measured by the heater current measuring means does not belong to the current range, based on the number of heaters less than the number of mounted heaters, the reference heater current, and the number of heaters mounted. , And calculate a current range of the heater current corresponding to the small number of heaters,
If the heater current measured by the heater current measuring means belongs to the current range, it is specified that the counter corresponding to the small number of heaters is a counter corresponding to the number of heaters that are not currently disconnected. The heater disconnection detecting device according to claim 3. Said counter specifying unit, if the heater current as a reference is Ib, implemented number of which heater m, the number of heaters seeking is n, the upper limit of the current range of the heater current corresponding to the number n I _upper ( The heater break detection device according to claim 4, wherein the lower limit of the current range of the heater current corresponding to n) and the number n is calculated as I _under (n).
I _upper (n) = Ib × (n + 0.5) / m
I _under (n) = Ib × (n−0.5) / m   The heater breakage determination means calculates the sum of the count values of the counters for each number of heaters, even when the number of heaters corresponding to the counter with the largest count value is smaller than the number of heaters mounted, 6. The heater disconnection determination is not performed if a value obtained by dividing the sum of the values by a count value incremented every power cycle is equal to or less than a predetermined value. The heater disconnection detection device according to the item.   The heater breakage determination means calculates the sum of the count values of the counters for each number of heaters, even when the number of heaters corresponding to the counter with the largest count value is smaller than the number of heaters mounted, The heater disconnection detection device according to any one of claims 1 to 5, wherein if the ratio of the maximum count value to the sum of the values is equal to or less than a predetermined value, the heater disconnection determination is not performed. .   When the number of heaters corresponding to the counter with the maximum count value is smaller than the number of heaters mounted, the heater disconnection determination means determines the counter with the maximum count value among the counters according to the number of heaters. 6. The heater break detection device according to claim 1, wherein the heater break is determined on condition that the number of times is the same continuously. 6. When the heater disconnection determining means determines that the heater is disconnected, it outputs the difference between the number of heaters corresponding to the counter with the maximum count value and the number of heaters mounted,
The heater break detection device according to any one of claims 1 to 8, wherein the alarm generation unit outputs a difference output from the heater break determination unit as a break alarm.   A power regulator comprising a power regulator for controlling a current flowing through the heater according to an operation amount of the temperature regulator, wherein the heater break detection device according to any one of claims 1 to 9 is mounted. The power adjustment device characterized by the above. A heater current measurement processing step in which the heater current measuring means measures a heater current, which is a current flowing through the heater, over a predetermined time interval or over a predetermined time;
A heater voltage measurement processing step in which a heater voltage measuring means measures a heater voltage, which is a voltage applied to the heater, over a predetermined time interval or a predetermined time;
The stability determining means monitors the amount of fluctuation of the heater current measured in the heater current measurement processing step and the amount of fluctuation of the heater voltage measured in the heater voltage measurement processing step, and the fluctuation amount of the heater current and the heater voltage is determined. A stability determination processing step for determining that the heater current and the heater voltage are stable if continuously within a predetermined range;
When it is determined that the stability is determined in the stability determination processing step, the counter specifying means is based on the heater current measured in the heater current measurement processing step and the heater voltage measured in the heater voltage measurement processing step. A counter identification processing step of identifying a counter corresponding to the measured heater voltage and the measured heater current among the counters according to the number of heaters, and incrementing a count value of the counter;
The heater disconnection determining means identifies the counter with the maximum count value among the counters by number of heaters, estimates that the number of heaters corresponding to the counter is the number of heaters not disconnected, and the estimated When the number of heaters is less than the number of heaters mounted, a heater disconnection determination processing step for determining that the heater is disconnected,
A heater disconnection detection method comprising: an alarm generation processing step for generating a disconnection alarm indicating that the heater is disconnected when the heater disconnection is determined in the heater disconnection determination processing step.

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