JP2007327852A - Method and apparatus for inspecting thermocouple - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable the total inspection of thermocouples to be carried out automatically and effectively without the need for any inspection-use heat source, by utilizing welding heat generated in a welding process of an automatic assembling line. <P>SOLUTION: The method for inspecting a thermocouple 1 which is carried out after the welding process of the automatic assembling line including the welding process of the thermocouple 1, comprises: a step of measuring an electromotive force of the thermocouple 1 which is caused by the welding heat generated for welding the thermocouple 1 in the welding process, by using a voltmeter 8; and a step of inspecting the thermocouple 1 automatically by using a control means 11 which determines whether it is normal or abnormal, based on the measured electromotive force. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inspection method and an inspection apparatus for automatically inspecting the total / normality of thermocouples in an automatic assembly line.

  In general, a thermocouple (thermocouple) is used as a thermoelectric thermometer that measures the temperature using the thermoelectromotive force generated at the contact point of dissimilar metals by the Seebeck effect, and the current generated by the thermoelectromotive force is passed through the coil. Thus, the electromagnetic force is generated, and the electromagnetic force is used as an actuator for opening and closing an electromagnetic valve or the like.

  An example of the latter is the application of a gas stove to a gas extinguishing safety device. In this gas extinguishing safety device, when a thermocouple is installed near the main burner of the gas stove and the main burner ignites, The contact of the thermocouple is heated by the flame and a thermoelectromotive force is generated. The current generated by the thermoelectromotive force flows to the coil of the solenoid valve unit to generate an electromagnetic force. Keep the passageway open. When the flame of the main burner disappears due to blow-off, spilling, etc., heating of the thermocouple contact stops and thermoelectromotive force, that is, electromagnetic force disappears, and the valve body is returned by the return spring to gas. Since the passage is closed, the release of gas is prevented.

  The thermoelectromotive force generated at the contact point of the thermocouple is determined by the type and temperature of the dissimilar metal, and copper-constantan, platinum-platinum rhodium, chromel-alumel, etc. are generally employed as the dissimilar metal combination. .

  By the way, when the thermocouple is mass-produced by an automatic assembly line as shown in FIG. 6, the assembly line includes a welding process for welding contacts of different metals. A thermocouple in which contacts of dissimilar metals are welded in the welding process is completed as a product through multiple subsequent processes.However, if the wrong metal is mixed in the line or welding in the welding process is poor. In such a case, the desired thermoelectromotive force is not generated in the thermocouple completed as a product, and this must be removed as a defective product by inspection.

  However, since it was not practical to inspect one million thermocouples that are mass-produced one by one, the quality of thermocouples was conventionally guaranteed by sampling inspection. Sampling inspection uses the Seebeck effect. The thermocouple contact is heated to a predetermined temperature by a heat source separately prepared for inspection, and the thermoelectromotive force generated at the contact is measured. Normal / abnormal was judged.

Patent Documents 1 and 2 disclose methods and apparatuses for inspecting temperature characteristics of electronic components such as piezoelectric vibrators and piezoelectric oscillators.
JP 2004-309552 A JP 2005-043332 A

  However, in the conventional method of guaranteeing the quality of thermocouples by sampling inspection, 100% quality assurance is impossible because all thermocouples are not inspected, and another heat source is used for inspection. There is a problem that it is inefficient because it is necessary to prepare and the inspection is performed offline.

  The present invention has been made in view of the above problems, and the object of the present invention is to automatically inspect all thermocouples using the welding heat of the welding process of the automatic assembly line without requiring a heat source for inspection. It is an object of the present invention to provide a thermocouple inspection method and inspection apparatus that can be efficiently performed efficiently.

  In order to achieve the above object, the invention according to claim 1 is a thermocouple welding in the welding process as a thermocouple inspection method performed after the welding process of the automatic assembly line including the thermocouple welding process. The electromotive force generated in the thermocouple by the welding heat at the time is measured, and the normal / abnormality of the thermocouple is automatically inspected based on the measured electromotive force value.

The invention according to claim 2 is a thermocouple inspection device implemented after the welding process of an automatic assembly line including a thermocouple welding process.
A voltmeter for measuring an electromotive force generated in the thermocouple by welding heat during welding of the thermocouple in the welding process;
An operator for connecting and disconnecting the voltmeter and the thermocouple;
Control means for determining whether the thermocouple is normal or abnormal based on the electromotive force value measured by the voltmeter, and for transmitting an operation signal to the voltmeter and the operator,
It is characterized by including.

  According to the thermocouple inspection method according to claim 1, which is performed using the inspection apparatus according to claim 2, the heat generated in the thermocouple due to welding heat at the time of welding of the thermocouple in the welding process, which is a previous process. An inspection process in which electric power is measured by a voltmeter and the control means determines whether the thermocouple is normal or abnormal based on the measured electromotive force value can be incorporated in the automatic assembly line. For this reason, it is possible to automatically and efficiently perform online inspection of all the thermocouples using the welding heat of the welding process of the automatic assembly line without requiring a heat source for inspection.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a front view of a thermocouple, FIG. 2 is a cross-sectional view of a thermosensitive part of the thermocouple, FIG. 3 is a block diagram showing the configuration of a thermocouple inspection apparatus according to the present invention, and FIG. FIG. 5 is a process diagram showing a thermocouple automatic assembly line incorporating an inspection method according to the present invention.

  A thermocouple 1 shown in FIG. 1 includes a temperature sensing portion 2 provided at the tip and two cables 3 and 4 extending from the temperature sensing portion 2. The temperature sensing portion 2 is configured as shown in FIG. As shown in FIG. 2, the rod-shaped conductor 5 connected to one cable 3, the first cylindrical conductor 6 disposed around the rod-shaped conductor 5, and the first cylindrical conductor 6 are connected to the other cable 4. For example, the second cylindrical conductor 7 is used.

  The rod-shaped conductor 5 and the first and second cylindrical conductors 6 and 7 are made of different metals, and the contact P between the rod-shaped conductor 5 and the first cylindrical conductor 6 is joined by welding. When the contact P is heated, a thermoelectromotive force is generated at the contact P due to the Seebeck effect.

  By the way, when the thermocouple 1 configured as described above is mass-produced in units of, for example, several million by an automatic assembly line as shown in FIG. 5, a welding process is included in the middle of the automatic assembly line. All the thermocouples 1 to which the contacts P are welded in the welding process are automatically inspected online by the inspection apparatus shown in FIG. 3 in the next inspection process.

  The inspection method according to the present invention uses welding heat during welding of the thermocouple 1 in the welding process, and measures the electromotive force generated in the thermocouple 1 due to residual heat after welding. It is characterized by automatically inspecting all the thermocouples 1 for normality / abnormality based on the electromotive force value, and is performed using the inspection apparatus shown in FIG.

  Here, the configuration of the inspection apparatus will be described with reference to FIG.

  In FIG. 3, reference numeral 8 denotes a voltmeter for measuring an electromotive force generated at the contact P of the thermocouple 1 due to residual heat after welding. The voltmeter 8 digitally displays the measured electromotive force. In FIG. 3, 9 is a welding torch.

  In FIG. 3, reference numeral 10 denotes an operator for electrically connecting and disconnecting the voltmeter 8 and the thermocouple 1. The operation of the operator 10 and the voltmeter 8 is controlled by the control means 11. The control means 11 transmits an operation signal to the voltmeter 8 and the operation element 10, and fulfills a function of determining normality / abnormality of the thermocouple 1 based on the electromotive force value measured by the voltmeter 8.

  Thus, as shown in FIG. 5, when mass production of several million thermocouples 1 is performed by an automatic assembly line in which an inspection process is incorporated after the welding process, in the welding process, the contact P of the thermocouple 1 is changed. Although welding is automatically performed by the welding torch 9, the thermocouple 1 that has been welded is automatically determined for all the normal / abnormal judgments in the next inspection process.

  That is, in the inspection process, the control means 11 shown in FIG. 3 transmits an operation signal to the voltmeter 8 and the operator 10 at an appropriate timing. Then, the operating element 10 operates to electrically connect the thermocouple 1 and the voltmeter 8, and the voltmeter 8 measures the electromotive force generated at the contact P of the thermocouple 1, and the measured electromotive force value Is transmitted to the control means 11 simultaneously with digital display.

  Here, the contact P of the thermocouple 1 is heated by the welding heat by welding, but in the next inspection process, the heating state is maintained by the residual heat of the welding heat. Generates electromotive force. This electromotive force is measured by the voltmeter 8. Therefore, in the present embodiment, the electromotive force of the thermocouple 1 in the inspection process is measured using the welding heat in the previous process, and no separate heat source for inspection is required.

  As described above, when the electromotive force value measured by the voltmeter 8 is transmitted to the control unit 11, the control unit 11 determines normality / abnormality of the thermocouple 1 based on the electromotive force value. If it is, the inspection is continued as it is, and if it is abnormal, the line is stopped and an error is displayed (NG display).

  Here, the normal / abnormal judgment of the thermocouple 1 is made as follows.

  That is, the thermocouple 1 exhibits different electromotive force characteristics depending on its type (in this embodiment, the type of the bar-shaped conductor 5 of the temperature sensing unit 2). For example, FIG. 4 shows the electromotive force characteristics of two types A and B of thermocouples 1A and 1B. For example, when the type A thermocouple 1A is flowing through the automatic assembly line, the control means 11 performs measurement. It is determined whether or not the measured electromotive force value is within the allowable range between H (maximum value) and L (minimum value). If it is within the allowable range, it is normal (OK) and out of the allowable range If it is, it is determined that there is an abnormality (NG).

  Therefore, when the type B thermocouple 1B is mixed in the automatic assembly line, it is determined that there is an abnormality from the difference in the electromotive force characteristics of both types A and B shown in FIG. Further, when the electromotive force having the expected magnitude is not generated in the thermocouple 1 due to poor welding in the welding process, the thermocouple 1 is determined to be abnormal.

  As described above, the thermocouple 1 flowing through the automatic assembly line is determined to be normal / abnormal in the inspection process after the welding process.

  Therefore, in the method of the present invention, the electromotive force generated in the thermocouple 1 by the welding heat at the time of welding of the thermocouple 1 in the welding process which is the previous process is measured by the voltmeter 8, and the measured electromotive force is measured. An inspection process in which the control means 11 determines whether the thermocouple 1 is normal or abnormal based on the value can be incorporated in the automatic assembly line. For this reason, the thermocouple 1 can be inspected automatically and efficiently for all of the thermocouples 1 by using welding heat without requiring a heat source for inspection, and 100% quality assurance is realized for the thermocouple 1. be able to.

  In addition, since the heat source for inspection is not necessary as described above, the facility can be simplified and the cost can be reduced, and the inspection can be automatically performed, so that labor can be saved.

It is a front view of a thermocouple. It is sectional drawing of the thermosensitive part of a thermocouple. It is a block diagram which shows the structure of the inspection apparatus of the thermocouple which concerns on this invention. It is a figure which shows the electromotive force characteristic with respect to the heating time of 2 types of thermocouples. It is process drawing which shows the automatic assembly line of the thermocouple incorporating the inspection method which concerns on this invention. It is process drawing which shows the conventional automatic assembly line of a thermocouple.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thermocouple 2 Temperature sensing part 3, 4 Cable 5 Rod-shaped conductor 6 1st cylindrical conductor 7 2nd cylindrical conductor 8 Voltmeter 9 Welding torch 10 Operating element 11 Control means P Contact

Claims (2)

An inspection method performed after the welding process of an automatic assembly line including a thermocouple welding process,
An electromotive force generated in the thermocouple due to welding heat during welding of the thermocouple in the welding process is measured, and normality / abnormality of the thermocouple is automatically inspected based on the measured electromotive force value. The thermocouple inspection method. An apparatus used for an inspection performed after the welding process of an automated assembly line including a thermocouple welding process,
A voltmeter for measuring an electromotive force generated in the thermocouple by welding heat during welding of the thermocouple in the welding process;
An operator for connecting and disconnecting the voltmeter and the thermocouple;
Control means for determining whether the thermocouple is normal or abnormal based on the electromotive force value measured by the voltmeter, and for transmitting an operation signal to the voltmeter and the operator,
A thermocouple inspection device characterized by comprising:

Images