JPS6322631Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement in a closure confirmation circuit for an inductive load circuit.

A split induction heating coil used in an induction heating device, which is an inductive load circuit, will be explained as an example.

The above-mentioned split-type induction heating coil is configured such that the conductor part that faces the workpiece with a predetermined gap and inductively heats the workpiece can be divided. For example, the induction heating coil C in the figure has a lead part 2 connected to the high frequency transformer CTr. The high frequency transformer is divided into a fixed conductor part Ca that is connected via
Near the outer center of the movable conductor portion Cb is fixed to the tip of the rod 4 of the fluid pressure cylinder 3 fixed at a predetermined position facing the CTr, and the rod 4 is moved back by operating the fluid pressure cylinder. to open the heating coil by displacing the movable conductor part Cb to the right in the figure. In this state, the workpiece W is carried to a predetermined heating position between both conductor parts Ca and Cb, and the rod 4 is advanced to close the movable conductor part Cb. After closing the heating coil C by displacing the part Cb to the left and bringing both end faces of the movable conductor part Cb into contact with both end faces of the fixed conductor part Ca, a high frequency power source (not shown) is turned on. This is a type of heating coil in which the closed heating coil C inductively heats the work W surrounded by a predetermined gap when the heating coil C is turned on, and is often used for hardening pins and journal parts of crankshafts.

In this type of induction heating coil, if the divided conductor parts are not properly closed, the heating coil will not be energized even if the high frequency power is turned on.
Therefore, the workpiece is not heated by induction. Therefore, as a conventional means for confirming the closing of the heating coil, when fluid is supplied to the chamber 31 of the hydraulic cylinder 3 that promotes the advancement of the rod 4 in the displacement mechanism of the movable conductor part Cb, both conductor parts Ca.Cb collide with each other. By utilizing the phenomenon that the fluid pressure increases when the contact is made, for example, there are devices that confirm the closing of the heating coil by closing the pressure switch, and detectors such as limit switches installed near the fixed conductor Ca side. and a contact provided on the side of the movable conductor portion Cb, which are arranged so that the contact closes a limit switch when the heating coil C is closed, thereby confirming that the heating coil is closed. However, in the former case, which utilizes the conventional phenomenon of increase in fluid pressure, even if, for example, a foreign object is present between the end surfaces of both conductor parts Ca and Cb that should collide, the fluid pressure increases in the same way as in the case of collision. Because of this phenomenon, there was a lack of accuracy, such as the heating coil being mistakenly thought to be closed, and malfunctions due to pulsation, which is unavoidable with a pressure switch, causing the heating coil to be mistakenly thought to be closed. In addition, in the latter case, which uses a limit switch and a contact, a cooling fluid is injected during quenching cooling, so waterproofing measures are required. Moreover, depending on the type of heat treatment equipment or the type of heating coil, it is often impossible to install a limit switch or a contactor.

Even in heating coils other than the above-mentioned split-type induction heating coils, even though the inductive load circuit is not closed due to loosening of the bolts that tighten the output terminal and the heating coil or other causes, There are cases where the power is turned on because there is no confirmation device. For example, in the case of a billet heater equipped with multiple heating coils connected in parallel to the same power source, if one heating coil among the multiple heating coils is not closed, the heating coil will pass through the multiple heating coils one after another while moving. The billet, which is heated to a certain temperature, is discharged without being heated to the predetermined temperature.

The present invention not only solves the above-mentioned drawbacks of conventional devices for checking the closure of split induction heating coils, but also provides a circuit that can widely confirm the closure of inductive load circuits with great accuracy. It is something.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A circuit according to the present invention will be explained with reference to an embodiment shown in the drawings in which the circuit is applied to a split type induction heating coil.

The fixed conductor part Ca of the split induction heating coil C has a lead. High frequency transformer C.Tr 2 through bar 2
The next side is connected. Above high frequency transformer C.Tr
The primary side of the is connected to a circuit that is supplied with power from a high-frequency power source (not shown), and a power-on switch is connected to the circuit.
By operating the MC, it is possible to supply and stop power to the high frequency transformer C.Tr.
The circuit of the present invention includes a current detector 1 in the circuit connected to the high frequency power supply on the primary side of the above high frequency transformer C.TR.
It has a configuration in which a circuit capable of applying a predetermined voltage from a commercial frequency power source E is connected via a movable contact Ry. As the current detector 1, for example, an overcurrent relay is used.

When checking the closed state of the induction heating coil C, move the rod 4 of the fluid pressure cylinder 3 forward,
A movable conductor portion fixed to the tip of the rod 4
After displacing Cb toward the fixed conductor Ca, the power supply switch MC remains open and the movable contact Ry
Close. As a result, the current of a predetermined voltage from the commercial frequency power source E is transferred from the commercial frequency power source E to the movable contact Ry.
--Flows through a circuit consisting of high frequency transformer C.Tr, movable contact Ry, current detector 1, and commercial frequency power source E. In this case, if the induction heating coil C is open for some reason, the high frequency transformer C is connected to the circuit.
Only the excitation current that excites the primary coil of the Tr flows, but when the induction heating coil C is in a closed state, the excitation current and the load current that induces an induced current in the workpiece W flow in the circuit. Therefore, the current value detected by the current detector 1 is larger in the latter case than in the former case. Therefore, if the set current value in the current detector 1 is set to be the sum of the excitation current value and the predetermined load current value, the movable contact
By closing Ry, the pointer indicated by current detector 1 becomes
It is possible to detect that the heating coil C is in the closed state if the current is above the set current value, and that the heating coil C is in the closed state if the current is below the set current value. In addition, if conductive inclusions such as chips are caught between the end faces of both conductor parts Ca and Cb, a current that is larger than the excitation current value but does not reach the set current value will flow. Therefore, detection is possible in this case as well.

When it is confirmed that the heating coil C is closed, the movable contact Ry is opened, and then the high frequency power is turned on and heat treatment of the workpiece W is started.

In the above embodiment, the closing of the heating coil C was confirmed by the pointer of the current detector 1, but since the present invention is entirely electrically constructed, a current exceeding the set current value flows through the current detector 1. It is also possible to incorporate this into an automatic device, such as by using the case as a condition for advancing the sequence.

When the present invention is applied to an apparatus using a normal type heating coil, a workpiece or a simulated load is inserted into the heating coil before turning on the heating power, and the commercial frequency power is connected as in the above embodiment. Needless to say, it is possible to detect whether the heating coil is closed by applying a predetermined voltage and detecting the current value of the current detector, regardless of whether the heating coil has a single turn or multiple turns.

The present invention makes good use of the characteristics of the inductive load circuit by passing current from a commercial frequency power source, which is separate from the inductive heating power source, to the transformer, so that the current flows when the load circuit is opened and closed. Since it is a purely electrical circuit that confirms the closing of the heating coil by changes in current value, (1) the open/closed state of the inductive load circuit can be detected extremely accurately, and (2) the It is a circuit that can be installed regardless of the model or shape of the heating coil, (3) it can be installed without modifying the heating coil or its vicinity, and (4) it can be installed on the primary side of the transformer. Since it connects the circuit, not only does it not require waterproofing measures like when using a conventional limit switch in a split-type heating coil, but it can also completely eliminate the drawbacks of conventional confirmation devices. ) Since it has an extremely simple configuration, it can be installed at low cost, and (6) it can be used not only for induction heating equipment but also as a closure confirmation circuit for other inductive load circuits, and its practical effects are extremely significant. be.

[Brief explanation of the drawing]

The figure is a circuit diagram showing an embodiment of the present invention connected to a heat treatment apparatus equipped with a split type induction heating coil. 1...Current detector, CTr...High frequency transformer, E
...Commercial frequency power supply, Ry...Movable contact.

Claims (1)

[Scope of utility model registration request] The induction heating device is characterized in that a circuit that is equipped with a current detector and is capable of applying a predetermined voltage from a commercial frequency power source is connected via a movable contact to the circuit that connects the induction heating power source to the primary side of the transformer. A closure confirmation circuit for an inductive load circuit.