JP2763038B2 - Furnace temperature distribution alarm - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a furnace temperature distribution alarm system, and more particularly to an alarm system for furnace temperature distribution in a furnace heated by a plurality of resistance heaters connected in series.

[0002]

2. Description of the Related Art When a workpiece to be heat-treated (hereinafter referred to as "work") is heat-treated in a furnace 1 having a resistance heater device (hereinafter sometimes referred to as "heater") H shown in FIG.
The temperature 1a is detected by the thermometer 2 and added to the controller 3, and the power to the heater H is controlled by the power regulator 4 under the control of the controller 3 so that a required furnace temperature is obtained. If the furnace 1 has a plurality of heaters H and their resistance values are unbalanced, the distribution of the furnace temperature is disturbed, which may cause defective products on the work.

Conventionally, in order to prevent the occurrence of defective products, a temperature sensor such as a plurality of thermocouple elements or temperature measuring resistors is attached to a work to monitor the temperature distribution.

[0004]

However, the method of directly attaching a temperature sensor to a work requires a troublesome work of attaching and detaching the temperature sensor for each batch of heat treatment.
There was a problem with workability. In a heat treatment system in which a workpiece is continuously transferred in a tunnel furnace, it is more difficult to attach a temperature sensor.

In some cases, the temperature distribution is monitored intermittently by attaching a temperature sensor to a dummy work instead of the actual work, instead of constantly monitoring the furnace temperature distribution during the heat treatment. And there was a problem in work quality assurance. Accordingly, an object of the present invention is to provide an apparatus for constantly monitoring the furnace temperature distribution of a resistance heating furnace and issuing an alarm for an abnormal furnace temperature distribution.

[0006]

SUMMARY OF THE INVENTION The present inventor has disclosed a furnace for heating by connecting a plurality of resistance heater devices in series.
If there is no change in the calorific value of each resistance heater device, it is noted that there is no temperature change in each part in the furnace and the temperature distribution is constant unless there is disturbance. Since the calorific value of the heater is determined by its power consumption, the calorific value does not change unless the resistance value of the resistance heater changes, and the calorific value also changes if the resistance value changes. When the furnace 1 shown in FIG. 1 heated by a plurality of resistance heater devices connected in series is operated for work processing, even if the temperature at the position of the thermometer 2 is stable under the control of the controller 3, If an unbalance occurs between the resistance values of the resistance heater device, the temperature distribution may be disturbed, which may cause defective products. SUMMARY OF THE INVENTION The present invention is intended to constantly monitor the resistance values of a plurality of resistance heater devices, detect the occurrence of an imbalance of a certain value or more among them, output an alarm, and prevent the occurrence of defective workpieces.

Referring to FIG. 1, a device for alarming abnormal distribution of furnace temperature according to the present invention comprises a plurality of resistance heater devices having a predetermined resistance value ratio.
In a furnace 1 heated by a series circuit of H _{1 to} H _n , a resistance detector 5 for detecting the resistance value of each heater device H _j at the time of operation of the furnace, and at the time of operation of all the detected heater devices H _{1 to} H _n It comprises a deviation detector 8 for detecting a deviation between a resistance value ratio and the predetermined resistance value ratio, and an alarm device 9 for outputting an alarm signal when the deviation is equal to or more than a predetermined alarm set value.

[0008]

[Action] In FIG. 1, when the furnace 1 is operating by supplying a load current I to the series circuit of the resistance heater device H ₁ to H _n, their resistance heater device H ₁ to H _n terminal voltage V ₁ of the since it is possible to measure the ~V _n, the load current I and terminal voltage V ₁ ~
Resistance detector 5 and a V _n can detect the operation when the resistance value R ₁ to R _n of each heater device H ₁ to H _n. From these detected operating resistance values, the operating resistance ratio of the heater device can be calculated by ratio calculating means (not shown). The deviation between the predetermined resistance value ratio and the resistance value ratio during operation of the heater device is calculated by the deviation detector 8 and sent to the alarm device 9. The alarm device 9 outputs an alarm signal when the deviation is larger than a predetermined alarm set value. Deviation of a predetermined resistance ratio and the heater unit H ₁ to H _n operating at the resistance value ratio of the
The alarm signal from the alarm 9 indicates the deviation between the operating heat output distribution of the devices and the desired heat output distribution, and thus the deviation of the operating furnace temperature distribution from the required furnace temperature distribution. Indicates the occurrence of an abnormality in the furnace temperature distribution.

The plurality of resistance heater devices H _{1 to} H _n all have the same resistance value, and the predetermined resistance value ratio n is unit value 1 (n = 1).
Case, the operation time of the resistance value based on the equal resistance value normalized, the deviation between a predetermined resistance ratio and the heater unit H ₁ to H _n operating at the resistance value ratio, during operation were normalized resistance It can be expressed as the difference between the maximum and minimum values. A predetermined resistance ratio unit value 1, and because operation when the resistance value ratio of the heater device H ₁ to H _n is between the maximum value and the minimum value of the operating time of the resistance values were normalized.

The predetermined resistance value ratio n is not a unit value 1 (n ≠ 1).
The case will be described. For example, other heating device H ₂ to H _n except heater device H ₁ on the inlet side of the furnace 1 has a resistance equal, only the resistance value of the heater unit H ₁ is another heater device H ₂ ~
It is assumed that it is twice (n = 2) the resistance value of H _n (selected heater device). Here, the selected heater device is a heater device having a resistance value serving as a reference for calculating the predetermined resistance value ratio n. In this case, the operation time of the resistance value R ₁ of the heater unit H ₁ by ratio adjuster 12 coupled by a dotted line in FIG. 1, a ratio corresponding to the predetermined resistance ratio n and the resistance value of the selected heater device (this Case (1 /
After the adjustment in (n) = 0.5), if the above-described processing in the case of the predetermined resistance value ratio n = 1 is performed, an alarm for the abnormal temperature distribution in the furnace can be output. Even if the predetermined resistance value ratio to the resistance value of any other heater device H _j is not a unit value of 1 it can be processed as in the case of the heater unit H _1.

Therefore, the furnace 1 having an arbitrary predetermined resistance value ratio n
The above processing and alarm can be output when the predetermined resistance value ratio n = 1 for the abnormal furnace temperature distribution. Accordingly, the object of the present invention is to provide a "device for constantly monitoring the furnace temperature distribution of a resistance heating furnace and issuing an alarm for an abnormal temperature distribution in the furnace".

[0012]

In the embodiment of EXAMPLES 1, a resistor detector 5 for each heating device H _j provided, through the load current I of the series heater circuit all the resistors detector 5, during operation of the heater device H _j The resistance _Rj is calculated as _Rj = _Vj / I using the terminal voltage _Vj .
However, instead of passing a large current, only a signal representing the magnitude of the load current I may be supplied to each resistance detector 5. In the illustrated example, the detection of the deviation of the standardized operating resistance values R _{1 to} R _n is performed by the maximum value detector 6, the minimum value detector 7, and the deviation detector 8.
The difference between the limit value set in the alarm limit setting device 10 and the output of the deviation detector 8 is obtained by the subtractor 11, and the obtained difference is added to the alarm device 9.

In order to prevent a defective product from being generated on the workpiece during the heat treatment, it is desirable to temporarily stop the furnace 1 in response to an alarm signal from the alarm device 9 and inspect the furnace. Each heater device H
_j can be constituted by a series or parallel circuit of a plurality of heating resistors. Since the alarm limit value to be set in the alarm limit setting device 10 differs depending on the workpiece to be heat-treated,
Preferably, it is determined by actually measuring each work by trial operation.

The alarm from the alarm device 9 not only indicates an abnormality in the furnace temperature distribution but also indicates a failure or deterioration of the heater device, so that it is possible to know the time of repair or replacement of these devices. The present invention is not limited to the illustrated example,
For example, a predetermined resistance value ratio of the heater device may be input and directly compared with the operating resistance value ratio of the heater device detected by the resistance detector 5.

[0015]

As described above in detail, the apparatus for alarming abnormal distribution of furnace temperature according to the present invention detects an abnormal distribution of furnace temperature by monitoring the resistance value during operation of the heater and outputs an alarm. It works.

(A) Since the furnace temperature distribution is constantly monitored, the rate of occurrence of defective products can be reduced and quality can be improved as compared with intermittent monitoring. (B) In the batch processing of the work, labor for attaching and detaching the temperature sensor for each lot can be omitted, and labor can be saved. (C) Aged deterioration of the heater device can be detected early, replaced with a good product in a timely manner, and good operating characteristics can be maintained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of one embodiment of the present invention.

[Explanation of symbols]

 1 Furnace 2 Thermometer 3 Controller 4 Power Controller 5 Resistance Detector 6 Maximum Detector 7 Minimum Detector 8 Deviation Detector 9 Alarm 10 Alarm Limit Setting 11 Subtractor 12 Ratio Adjuster.

Claims (3)

(57) [Claims] In a furnace heated by a series circuit of a plurality of resistance heater devices having a predetermined resistance value ratio n, a resistance detector for detecting a resistance value of each heater device when the furnace is operated, and operation of all detected heater devices. Furnace temperature abnormal distribution alarm comprising: a deviation detector for detecting a deviation between a ratio of the hourly resistance value and the predetermined resistance value ratio n; and an alarm device for outputting an alarm signal when the deviation is equal to or more than a predetermined alarm set value. apparatus. 2. The alarm device according to claim 1, wherein when the plurality of resistance heater devices have the same resistance value and a predetermined resistance value ratio n is a unit value (n = 1), all the heater devices are activated. An abnormal furnace temperature distribution alarm device in which a resistance value is standardized based on the equal resistance value, and a difference between a maximum value and a minimum value of the standardized resistance values during operation of all the heater devices is set as the deviation. 3. The alarm device according to claim 1, wherein, when the predetermined resistance value ratio n is not a unit value (n ≠ 1), the operating resistance values of all the heater devices are calculated based on the predetermined resistance value ratio n. After adjusting the ratio by the ratio determined based on the resistance value of the selected heater device and the predetermined resistance value ratio n, standardization is performed based on the resistance value of the selected heater device, and when the standardized all heater devices are operated. An abnormal furnace temperature distribution alarm device in which a difference between a maximum value and a minimum value in resistance values is used as the deviation.