JPH06201484A - Method and apparatus for detecting failure of thermocouple - Google Patents

Abstract

PURPOSE:To quickly detect a short circuit of a thermocouple o prevent a failure of a band heater by comparing a temperature rising rate of heating temperature with a preset reference value. CONSTITUTION:Heating temperature T by a band heater 2 is detected by a thermocouple 3 and applied to a calculation part 6. The calculation part 6 obtains a temperature rising rate X=DELTAT/DELTAt (t: time) from the heating temperature T and applies the obtained temperature rising rate X to a failure detecting part 7. The failure detecting part 7 compares the temperature rising rate X obtained by the calculation part 6 with a preset reference value Y, and if the temperature rising rate X is larger than the reference value Y, it is determined to be normal. If the temperature rising rate X is at the reference value Y or lower, however, whether or not detection results from a temperature rising region detecting part 5 are in a temperature rising region is further determined. If they are not in the temperature rising region, a normal temperature region, that is normal, is determined, and if they are in a temperature rising region, the thermocouple 3 is determined to have been shorted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermocouple abnormality detecting method and device attached to a heating device of an injection molding machine.

[0002]

2. Description of the Related Art Conventionally, a heating device such as a heating cylinder or an injection nozzle in an injection molding machine is attached to heat a heating part to a target temperature. Specifically, a band heater is wrapped around the outer periphery of the heating portion, the heating portion is heated by this band heater, and the heating temperature of the heating portion is detected by a thermocouple (temperature sensor), and this heating temperature is set as a preset target. Feedback control with respect to the heating temperature was performed so as to match the temperature.

[0003]

By the way, normally, this kind of heating device is provided with an abnormality detecting device for detecting an abnormality of the thermocouple, but in the conventional abnormality detecting device, the cause of the abnormality is mainly generated. Since the thermocouple has a wire breakage abnormality, most of the wire breakage detection functions (burnout) were not considered for short-circuiting abnormality.

However, in the heating device of the injection molding machine, the thermocouple is intentionally short-circuited and only the operation confirmation work for the band heater or the like is performed, or the thermocouple is crushed for some reason and the short-circuit state occurs. May occur. When the worker operates the heating device without knowing such a short-circuited state, the detected heating temperature value is fixed near the ambient temperature, so that it is actually heated to a high temperature state. However, the maximum output (100% output) of the control amount for the band heater continues, which may result in failure of the band heater due to the inability to control the temperature, or even fire.

The present invention solves the problems existing in the prior art as described above, and the failure of the band heater or the occurrence of fire can be surely prevented by promptly detecting the short circuit abnormality of the thermocouple. An object of the present invention is to provide a pair abnormality detection method and apparatus.

[0006]

A method for detecting an abnormality of a thermocouple according to the present invention uses heating of a heater 2 when detecting a short circuit abnormality of a thermocouple 3 used for detecting a heating temperature T (° C.) by the heater 2. The temperature increase rate Z = ΔT / of the heating temperature T detected by the thermocouple 3 while detecting the temperature rising region Zu
By obtaining Δt (t: time) and comparing the temperature increase rate X with a preset reference value Y, when the temperature increase rate X in the temperature rising region Zu is equal to or less than the reference value Y, a short circuit abnormality of the thermocouple 3 occurs. It is characterized in that it is detected as. In this case, the temperature rising region Zu is detected by the magnitude of the control amount for the heater 2 of the feedback control system with respect to the heating temperature T.

Further, the thermocouple abnormality detecting device 1 according to the present invention includes a temperature rising region detecting section 5 for detecting the temperature rising region Zu by the heater 2, and a temperature increase rate X of the heating temperature T detected by the thermocouple 3. The temperature increase rate X calculated by the operation unit 6 is compared with a preset reference value Y, and when the temperature increase rate X in the temperature rising region Zu is equal to or less than the reference value Y, the thermocouple 3 is short-circuited. It is characterized by including an abnormality detection unit 7 that detects an abnormality. It should be noted that the temperature rising region detection unit 5 is set to the heating temperature T.
The temperature rise area Zu is detected by the control amount of the feedback control system for the heater 2.

[0008]

OPERATION METHOD AND APPARATUS FOR Detecting Thermocouple Abnormality 1
According to the above, first, the temperature rising area detection unit 5 detects the temperature rising area Zu due to the heating of the heater 2. In this case, the temperature rising region Zu is detected by the duration of the maximum control amount (100% output) for the heater 2 of the feedback control system with respect to the heating temperature T. In addition, during the period other than the temperature rising region Zu,
For example, the control amount of the constant temperature region Zc where the heating temperature T is relatively stable after the end of the temperature rising region Zu becomes small (less than 100% output).

On the other hand, the temperature rise rate X = ΔT / Δt of the heating temperature T detected from the thermocouple 3 is obtained by the calculation unit 6. Then, the abnormality detection unit 7 compares the temperature increase rate X with a preset reference value Y, and when the temperature increase rate X in the temperature rising region Zu is equal to or less than the reference value Y, it is detected as a short circuit abnormality of the thermocouple 3. . That is, in the temperature rising region Zu, if the thermocouple 3 is normal, the temperature increase rate X of the heating temperature T detected by the thermocouple 3 always exceeds the reference value Y, but the thermocouple 3
When the short circuit abnormality occurs in the temperature rise rate X becomes equal to or lower than the reference value Y.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments according to the present invention will be described in detail with reference to the drawings.

First, a schematic structure of a heating device and an injection molding machine equipped with the abnormality detecting device according to this embodiment will be described with reference to FIGS. 1 and 2.

In FIG. 2, reference numeral 10 shows a part of the injection device in the injection molding machine. Reference numeral 11 is a heating cylinder having a screw 12 built therein, and an injection nozzle 13 is provided at the front end portion. The heating cylinder 11 and the injection nozzle 13 are provided with band heaters 2 and 14 wound around the outer peripheral surface thereof, respectively, and a thermocouple 3 for detecting the heating temperature of the heating cylinder 11 and the injection nozzle 13.
(The injection nozzle 13 side is not shown). The thermocouple 3 and the band heater 2 (14) are connected to the temperature controller 1
6 to thereby configure the heating device 15, and the temperature controller 16 is connected to the host computer 17 via a communication line such as an optical fiber cable.

On the other hand, as shown in FIG. 1, the thermocouple 3 is connected to a temperature detecting section 21 built in the temperature controller 16. As a result, the heating temperature (temperature detection value) T (° C.) is obtained from the temperature detection unit 21, and the obtained heating temperature T is given to the control unit 22. On the other hand, the setting unit 23 sets the target temperature Ts, and the target temperature Ts is also given to the control unit 22. Therefore, the control unit 22 compares the detected heating temperature T with the target temperature Ts, obtains the deviation between the two, and generates a control signal (control amount) Sc based on the deviation. Then, the control signal Sc is applied to the driver 24 to control the operation of the band heater 2, and feedback control is performed so that the heating temperature T matches the target temperature Ts.

Next, the configuration of the abnormality detecting device 1 constituting the essential part of the present invention will be specifically described with reference to FIG. It should be noted that the host computer 17 shown in FIG. 1 extracts and shows only the functional units related to the present invention.

First, the heating temperature T obtained from the temperature detecting unit 21 is transmitted to the communication unit 25 built in the host computer 17 through the communication unit 25 built in the temperature controller 16 and the communication line. The control signal Sc given from the control unit 22 to the driver 24 is also transmitted to the communication unit 31 via the communication unit 25 and the communication line.

On the other hand, the host computer 17 incorporates the abnormality detection device 1 according to the present invention. The abnormality detection device 1 includes a temperature rising region detection unit 5, a calculation unit 6 that calculates a temperature increase rate, and an abnormality detection unit 7, and each unit is a host computer 1
It is configured as a part of the functions of 7.

The temperature rising region detection unit 5 detects the temperature rising region Zu by the band heater 2, and the temperature rising region Zu is the maximum duration (100% output) of the control signal Sc obtained from the communication unit 31. It has a function to detect as. Then, the detection result of the temperature rising region Zu is given to the abnormality detection unit 7.

The calculation unit 6 also has a function of obtaining the temperature increase rate X from the heating temperature T. That is, the calculation unit 6 is the communication unit 3
From the heating temperature T obtained from 1, the temperature rise rate X = ΔT / Δ
t (t: time) is calculated. Then, the obtained temperature increase rate X is given to the abnormality detection unit 7.

Further, the abnormality detecting section 7 compares the temperature increase rate X obtained by the calculating section 6 with a preset reference value Y, and the temperature increase rate in the temperature increasing area Zu detected by the temperature increasing area detecting section 5. It has a function of detecting when X is equal to or less than the reference value Y as a short circuit abnormality of the thermocouple 3. Reference numeral 32 is an alarm unit connected to the output side of the abnormality detection unit 7.

Next, the operation of the abnormality detecting device 1 according to the present invention will be described with reference to the flow charts shown in FIGS.

First, the heating device 15 is operated to supply electric power to the band heater 2, thereby heating the heating cylinder 11 (heating portion).
To heat. At this time, the heating temperature T by the band heater 2
Is detected by the thermocouple 3 (step 41), and the heating temperature T is given to the calculation unit 6. Then, the calculation unit 6 obtains the temperature rise rate X = ΔT / Δt from the heating temperature T, and the obtained temperature rise rate X is given to the abnormality detection unit 7 (step 4).
2).

Further, the abnormality detecting section 7 compares the temperature increase rate X obtained by the calculating section 6 with a preset reference value Y (step 43), and if the temperature increase rate X exceeds the reference value Y,
It is judged to be normal (step 44). However, when the temperature increase rate X is less than or equal to the reference value Y, the temperature rise region detection unit 5 further
It is determined whether or not the detection result from is the temperature rising region Zu. In this case, since the predetermined elapsed time from the start of heating is the temperature rising region Zu shown in FIG. 3, the heating temperature T rises as time passes. In the temperature rising region Zu, the magnitude of the control signal (control amount) Sc for the band heater 2 in the feedback control system is maximum, that is, 100% output, while the heating temperature T after the end of the temperature rising region Zu is The control signal Sc in the stable constant temperature region Zc becomes less than 100% output. Therefore, the temperature rising region detection unit 5 controls the control signal S
While monitoring c, the period in which the size is maximum is determined as the temperature rising region Zu, and the detection result is given to the abnormality detecting unit 7. In this case, if it is not the temperature rising region Zu, it is determined as the constant temperature region Zc, that is, normal (steps 45 and 44), and the temperature raising region Zc is determined.
If so, it is determined that the thermocouple 3 is short-circuited (steps 45 and 46). Further, the abnormality detecting section 7 gives an alarm signal to the alarm section 32, and the alarm section 32 issues an abnormal alarm (step 47).

Therefore, according to the abnormality detecting method and apparatus 1 of the present invention, the short-circuit abnormality of the thermocouple 3 can be detected promptly, and particularly, the short-circuit state of the thermocouple 3 such as the heating portion in the injection molding machine can be detected. It is extremely effective when there is a risk of occurrence.

The embodiment has been described in detail above.
The present invention is not limited to such an embodiment.
For example, the temperature rise region is detected by the magnitude of the control amount for the heater of the feedback control system with respect to the heating temperature, but it may be detected by another method such as a set time elapsed from the start of temperature rise. In addition, the detailed configuration, method, and the like can be arbitrarily changed without departing from the scope of the present invention.

[0025]

As described above, the thermocouple abnormality detecting method according to the present invention detects the temperature rise area due to heating of the heater when detecting the short circuit abnormality of the thermocouple used for detecting the heating temperature by the heater. , The temperature rise rate of the heating temperature detected by the thermocouple is obtained, and by comparing this temperature rise rate with a preset reference value, when the temperature rise rate in the temperature rising region is below the reference value, the thermocouple short circuit abnormality Therefore, the short-circuit abnormality of the thermocouple can be detected promptly and the failure of the band heater, the occurrence of fire, etc. can be reliably prevented.

Further, the thermocouple abnormality detecting apparatus according to the present invention includes a temperature rising area detecting section for detecting a temperature rising area due to heating of the heater, and an arithmetic section for obtaining a temperature increase rate of the heating temperature detected by the thermocouple. Since the temperature detection unit compares the temperature increase rate obtained by the calculation unit with a preset reference value, and includes a failure detection unit that detects when the temperature increase rate in the temperature rising region is equal to or lower than the reference value, as a thermocouple short circuit abnormality, The remarkable effect that the above-mentioned abnormality detection method can be easily and surely carried out is exhibited.

[Brief description of drawings]

FIG. 1 is a block system diagram of a heating device including a thermocouple abnormality detection device according to the present invention;

FIG. 2 is a partial cross-sectional configuration diagram of an injection molding machine including the heating device,

FIG. 3 is a temperature rise characteristic diagram of the heating device,

FIG. 4 is a flow chart showing a thermocouple abnormality detection method according to the present invention;

[Explanation of symbols]

 1 Abnormality Detection Device 2 Heater 3 Thermocouple 5 Temperature Raising Area Detection Unit 6 Calculation Unit 7 Abnormality Detection Unit T Heating Temperature t Time Zu Temperature Raising Area X Temperature Rise Rate Y Reference Value

Claims (5)

[Claims] 1. When detecting a short circuit abnormality of a thermocouple used for detecting a heating temperature by a heater, a temperature rising region due to heating of the heater is detected, and a temperature increase rate of the heating temperature detected by the thermocouple is obtained. A thermocouple abnormality detection method, comprising detecting a temperature rise rate in a temperature rising region equal to or lower than a reference value as a thermocouple short circuit abnormality by comparing a temperature rise rate with a preset reference value. 2. The method for detecting an abnormality of a thermocouple according to claim 1, wherein the temperature rising region is detected by the magnitude of the control amount for the heater of the feedback control system with respect to the heating temperature. 3. A thermocouple abnormality detecting device for detecting a thermocouple short-circuit abnormality used for detecting a heating temperature by a heater, and a temperature raising area detecting section for detecting a temperature raising area due to heating of the heater, and detection by the thermocouple. The temperature rise rate calculated by the calculation unit is compared with the temperature rise rate calculated by the calculation unit, and if the temperature rise rate in the temperature rising region is less than the reference value, the thermocouple short-circuit fault occurs. An abnormality detecting device for a thermocouple, comprising: 4. The thermocouple abnormality detection device according to claim 3, wherein the temperature rising region detection unit detects the temperature rising region based on the magnitude of the control amount for the heater of the feedback control system with respect to the heating temperature. 5. The thermocouple abnormality detection device according to claim 3, which is applied to a heating device of an injection molding machine.