JP4644380B2 - Method of detecting contact failure of high frequency induction heating coil - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for detecting a contact failure of a high-frequency induction heating coil when a workpiece to be heated or a workpiece to be hardened, such as a crankshaft or a camshaft, is heated at a high frequency. when high-frequency heating, to contact failure detecting method of the high-frequency induction heating coil for detecting a contact abnormality between the disk-shaped transformer to power the high-frequency induction pressure heat coil and the high-frequency power during heating.
[0002]
[Prior art]
As shown in FIG. 4, for example, four-cylinder gasoline engine (or diesel engines) work (crankshaft) 100, the pin portions 120,140,160,180 and the journal portion 110, 130, and 150 by forging, 170 and 190 are integrally formed.
Conventionally, induction hardening of the pin portions 120, 140, 160, 180 and the journal portions 110, 130, 150, 170, 190 of the workpiece (crankshaft) 100 is performed around the central axis X with respect to the workpiece (crankshaft) 100. while rotating, to the pin portion 120,140,160,180 and a journal portion 110,130,150,170,190, respectively high-frequency induction heating coil (hereinafter, simply referred to as high-frequency heating coil) is placed on, the rotation Followed by heating and cooling, induction hardening is applied.
[0003]
In high-frequency induction heating of the workpiece (crankshaft) 100, which is a workpiece to be hardened, simultaneously heating a plurality of locations is progressing from the improvement of productivity and quenching quality.
Now, as shown in FIG. 5, the high-frequency heating power output from the high-frequency oscillator is inserted between a high-frequency oscillator (not shown) and, for example, four high-frequency heating coils 2a, 2b, 2c, and 2d. The disk-shaped transformer T of each of the matching portions 3a, 3b, 3c, 3d that supplies power to the high-frequency heating coils 2a, 2b, 2c , 2d is a pin portion 120, 140, 160, 180 of the workpiece (crankshaft) 100. Further, in order to simultaneously heat a plurality of locations of the journal portions 110, 130, 150, 170, and 190, those having a thickness as thin as possible are used.
[0004]
Each of the connection portions 8 of the disk-shaped transformer T and the high-frequency heating coils 2a, 2b, 2c , and 2d is connected to the disk-shaped transformer T as shown in the A and A enlarged views of FIG. The contact convex portions 8a and 8b formed in the shape of a truncated cone on the secondary side T2 are formed in the shape of a truncated cone on the high-frequency heating coils 2a, 2b, 2c and 2d, respectively. The contact recesses 8c and 8d are connected so as to be fitted, and a high-frequency current is supplied from the disk-shaped transformer T to the high-frequency heating by the connection between the contact protrusions 8a and 8b and the contact recesses 8c and 8d. It will flow to the coils 2a, 2b, 2c and 2d.
[0005]
[Problems to be solved by the invention]
However, conventionally, the contact convex portions 8a of the disk-shaped transformer T, 8b and the high-frequency heating coil 2a, 2b, 2c, the contact recess 8c of 2d, the visual confirmation of the respective contact child surface with 8d, the disc shape transformer T and the high-frequency heating coil 2a, 2b, 2c, considering the layout of the 2d difficult. Even if the contact state between the disk-shaped transformer T and the high-frequency heating coils 2a, 2b, 2c , and 2d looks good, the electrical contact may be insufficient. Thus, the hardened state of the workpiece (crankshaft) 100 is visually confirmed.
[0006]
In the case of high frequency heating at a single location, the heating conditions (high frequency output voltage, current, power, or drive frequency) from the high frequency oscillator as the power source are compared, or a protection circuit incorporated in the power source itself, etc. Although an abnormal state can be determined by an alarm, in the case of simultaneous heating at a plurality of locations, depending on the heating conditions, the high-frequency heating may be completed without an alarm circuit with a built- in power supply operating. In such a state, one by one the quality of the heating must be confirmed with the naked eye, there is a problem that requires a great effort.
[0007]
The present invention has been made in view of such a point, and the object thereof is to solve the above-mentioned problem, and when a plurality of locations of the work (crankshaft) 100 are simultaneously subjected to high-frequency induction heating, the disc-shaped transformer T of the alignment portion is provided. and the high-frequency heating coil 2a, 2b, 2c, is to propose a contact failure detection method of the high circumferential NamiKa heat coil for detecting a failure of the electrical contact between 2d.
[0008]
[Means for Solving the Problems]
Upon the configuration of the present invention for achieving the object, high-frequency NamiKa heat coils 2a, 2b, 2c, by 2d, simultaneously high frequency induction heating the plurality of positions of the workpiece (crankshaft) 100 of the object to be heated, It is as follows.
[0009]
The present invention, through the matching portion of the high-frequency oscillator or al multiple, supplies power to each of the high-frequency induction heating coil, the workpiece during high frequency induction heating, is input to each of the plurality of matching portions that detects an input current, 1) the value of the input current to the matching portion of one of said plurality of matching portions, or an over-current exceeding the roughness or dimethyl set current value, or, 2) the value of one of the input current to the matching portion of the front Symbol plurality of matching portions, the plurality of average input current value of the sum of the input current inputted divided by the total number of said plurality of matching portions to matching unit the difference between the, when an unbalanced current exceeding a rough or set beforehand has been allowed unbalance current, previous SL and one of the matching portion, the contact failure is detected with the high-frequency induction heating coil connected thereto It is a method.
[0010]
The present invention is a method in which, after the contact failure is detected, an alarm signal for stopping high-frequency induction heating is output to the one matching portion in which the contact failure is further detected.
[0011]
The present invention is a method in which each of the plurality of matching units includes a matching capacitor and a disk-type transformer formed in a parallel resonant circuit.
[0012]
The present invention is a method in which an input current input to each of the plurality of matching units is detected by a Rogowski type current detecting means.
[0013]
In the present invention, the disk-shaped transformer and a matching capacitor for reactive power compensation constitute the matching section, and a high frequency is provided on the input side of the matching section, that is, on the primary side of the disk-shaped transformer of the matching section. by arranging the current detector at all times by monitoring the input current, the matching unit input current detecting circuit unit, an electrical contact not Yoken unloading of the high frequency heating coil and the disk-shaped transformer How to do it.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described in detail with reference to the drawings.
[First embodiment]
FIG. 1 is a circuit diagram showing an embodiment of the induction hardening method of the present invention , and is a diagram for monitoring the input current to the high frequency heating coil through each matching section from the matching section side. FIG. 2 is a configuration circuit diagram of a matching unit input current detection circuit unit in FIG. 1.
[0015]
Induction hardening NyuSo location in an embodiment of the present induction hardening method, a material to be heated, a four-cylinder engine which material consists of steel or a carbon steel workpiece (crankshaft) is for induction hardening. In the present invention , the high-frequency heating coil group 2 is placed on the outer periphery of the cylindrical portion of each of the pin portions 120, 140, 160, 180 and the journal portions 110, 130, 150, 170, 190 of the workpiece (crankshaft) 100. The work piece (crankshaft) 100 is rotated about its central axis X so that the high-frequency heating coil group 2 follows the outer circumference of the cylindrical part, while the cylindrical part (or the cylindrical part, fillet R part and fillet part). ) Is then induction-heated, and then the pins and journals are cooled by cooling means to quench the surfaces of the pins and journals.
[0016]
The schematic of FIG. 1, one of the high-frequency oscillator 6 and the high-frequency heating power output from the (1KHz～30kHz output RF power), the high-frequency NamiKa heat four high-frequency heating coil 2a of the coil groups 2 , 2b, 2c, and 2d are supplied via respective switching units 11a, 11b, 11c, and 11d that are switched by a control device (not shown) via matching units 3a, 3b, 3c, and 3d connected thereto, respectively. To be connected. At the same time, a matching unit input current detection circuit unit 30 shown in FIG. 2 is connected to monitor the input currents to the matching units 3a, 3b, 3c, and 3d.
[0017]
After the four switching devices 11a, 11b, 11c , and 11d, the pin portion and the journal portion of the work (crankshaft) 100 are heated, and as shown in FIG. Matching portions 3a, 3b, 3c and 3d made of a mold transformer T and the four high-frequency heating coils 2a, 2b, 2c and 2d are connected. Here, the number of the high-frequency heating coils 2a, 2b, 2c , and 2d connected to the matching portions 3a, 3b, 3c , and 3d is four, that is, four heating points.
[0018]
Then, for detecting the input current to the matching unit 3a, 3b, 3c, each 3d,該整engagement portion 3a, 3b, 3c, the respective input side of the 3d, Rogowski type shown in FIG. 3 (a) High-frequency current detectors 20a, 20b, 20c, and 20d are respectively disposed and connected, and signals 21a, 21a, 20b, 20c , and 20d for detecting the respective input currents obtained from the high-frequency current detectors 20a, 20b, 20c , and 20d. 21b, 21c, and 21d are output to the matching unit input current detection circuit unit 30.
[0019]
As shown in FIG. 2, the matching unit input current detection circuit unit 30 is supplied with the input current signals 21a, 21b, 21c and 21d, and an overcurrent detection circuit 31 and an average current detection circuit for the input current. 32 and the current balance detection circuit 33, and an overcurrent abnormality detection circuit 34.
The overcurrent detection circuit 31 receives an input overcurrent value setting signal, and the current balance detection circuit 33 receives an allowable unbalance current value setting signal.
[0020]
Input current signals 21a, 21b, 21c , and 21d from the high-frequency current detectors 20a, 20b, 20c, and 20d that are input to the matching unit input current detection circuit unit 30 are the overcurrent detection circuit 31 and the average. When input to the current detection circuit 32 and the current balance detection circuit 33 and the overcurrent detection circuit 31 exceeds the input overcurrent set value, the input overcurrent signals 41a, 41b, 41c, 41d is output from the average current detection circuit 32, and the average current value signal 42 of each of the input current signals 21a, 21b, 21c , 21d is output from the average current detection circuit 32 from the current balance detection circuit 33. and the average current value signal 42, compared the respective input current signals 21a, 21b, 21c, the balance value of the 21d When exceeding the allowable unbalance current setpoint, in response to the input current signal, the unbalance current signal 43a, respectively, 43 b, 43c, 43d is outputted.
[0021]
Furthermore, the input overcurrent signals 41a, 41b, 41c and 41d and the unbalanced current signals 43a, 43b, 43c and 43d respectively outputted from the overcurrent detection circuit 31 and the current balance detection circuit 33 are the overcurrent abnormalities. is input to the detection circuit 34 monitors both of these signals, when either signal is input, in response to the input current signal, each of the matching portion 3a, 3b, 3c, 3d overcurrent Abnormal alarm signals 44a, 44b, 44c, and 44d are output to the outside.
[0022]
Here, when the electrical contact state between the matching portions 3a, 3b, 3c , 3d and the high-frequency heating coils 2a, 2b, 2c , 2d is poor, the matching portions 3a, 3b, 3c , 3d The inductance measured from the input side of the disk-shaped transformer T is not an inductance value between the high-frequency heating coils 2a, 2b, 2c , 2d and the workpiece (crankshaft) 100, but the disk-shaped transformer. This is the inductance value on the primary side of T. The value is several mH compared to several tens of μH in the case of a steady value.
[0023]
Therefore, if the contact state between the disk-shaped transformer T of the matching portions 3a, 3b, 3c and 3d and the high frequency heating coils 2a, 2b, 2c and 2d is poor, the matching portions 3a, 3b and 3c , 3d is greatly different from the steady state, and when a plurality of locations of the workpiece (crankshaft) 100 are simultaneously heated in such a state, the matching sections 3a, 3b, The input currents to 3c and 3d are larger than the steady values.
[0024]
In this case, although the output state of the high-frequency oscillator 6 depends on the heating state at a plurality of locations, the heating conditions in the high-frequency oscillator 6, that is, the high-frequency voltage, current, power, and drive frequency, as the number of heating stages increases. Is less than the steady state value. In such a case, the matching unit input current detection circuit unit 30 is effective, and the input current to the matching units 3a, 3b, 3c , and 3d is larger than a steady value. by a proper value overcurrent setting value, the detected abnormal overcurrent abnormality alarm signal 44a, and outputs 44b, 44c, and 44d, it is possible to quickly stop the high-frequency induction pressure heat.
[0025]
Next, each of the high-frequency current detectors 20a, 20b, 20c, and 20d shown in FIG. 3A has a Rogowski probe 22 that detects an input current to the matching portions 3a, 3b, 3c , and 3d. As shown in FIG. 3B, the Rogowski probe 22 is wound around the input power supply line to the matching portions 3a, 3b, 3c , and 3d once.
Each of the high-frequency current detectors 20a, 20b, 20c , and 20d passes through the conductive wire 23 in one thin long flexible hollow tube 22a, and the conductive wire extends from the through end 23b of the hollow tube 22a. 23 has the Rogowski probe 22 wound around the outer peripheral surface of the hollow tube 22a in a coil shape at a constant interval. The material of the hollow tube 22a that is used is used having a high insulating property, the conductive wire 23, the high-frequency heating coil 2a, 2b, 2c, 2d voltage wound around the outer peripheral surface of the hollow tube 22a The one having a sufficient withstand voltage value for a voltage higher than the value is used.
[0026]
The high-frequency current detectors 20a, 20b, 20c , and 20d have a 50Ω coaxial cable 24 connected to the output end of the Rogowski probe 22 and a 50Ω termination resistor connected to the matching sections 3a, 3b, The input current value to 3c and 3d is converted into a voltage value. The conversion ratio between the input current and voltage to the matching sections 3a, 3b, 3c and 3d is determined by the number of coils wound around the hollow tube 22a. In addition, as shown in FIG. 3B, the Rogowski probe 22 is wound around the input tube to each of the matching portions 3a, 3b, 3c , and 3d once, so that it is coaxial with the hollow tube 22a. the connection point between one end of the cable 24, tubular holding member 26 for mechanically connecting the winding tip of the beginning of the hollow tube 22a is provided. A BNC connector 25 is connected to the other end of the coaxial cable 24.
Here, SL before being used high-frequency current detector 20a, 20b, 20c, 20d, it is also possible to install the matching unit 3a, 3b, 3c, 3d disc type transformer in T that shown in FIG. 1 is there. The Rogowski probe 22 need not be replaced.
[0027]
As described above, according to the present embodiment, the electrical contact state between the matching portions 3a, 3b, 3c , 3d and the high-frequency heating coils 2a, 2b, 2c , 2d is visually observed or after heating. There is no need for visual confirmation of the hardened state of the workpiece (crankshaft) 100 , and the contact state defect can be detected very easily.
[0028]
As described above, the technology of the present invention is not limited to the technology in the above-described embodiment, and may be a means of another aspect that performs the same function, and the technology of the present invention is within the scope of the above configuration. Various modifications and additions are possible.
[0029]
【The invention's effect】
According to the induction hardening method of the present invention As apparent from the above description, through the matching portion of the high-frequency oscillator 6 or al multiple, supplies power to each of the high-frequency NamiKa heat coils, the the workpiece (crankshaft) 100 during high frequency induction heating, detects an input current input to each of the plurality of matching portions, 1) the value of one of the input current to the matching portion of the plurality of matching portions but whether the overcurrent exceeds a rough or dimethyl set current value, or, 2) the value of one of the input current to the matching portion of the plurality of matching portions, to said plurality of matching portions when the sum of the input current inputted difference between the average input current value divided by the total number of said plurality of matching portions are unbalanced current exceeding a rough or set beforehand has been allowed unbalance current value, before Symbol and one of the matching portion, the high-frequency connected thereto Since poor contact between the pressurized heat coil is detected, when at the same time high-frequency induction heating plurality of locations of said workpiece (crankshaft) 100, a matching section, in contact with the disc-shaped transformer contacts of the high-frequency heating coil It is possible to detect a failure in electrical contact with the part.
[0030]
In particular, since the contact failure can be detected while monitoring the input current to the matching section during heating, it is possible to prevent the occurrence of defective products with quenching quality in continuous production, and to improve production efficiency. There is an excellent effect of being able to.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an embodiment of an induction hardening method according to the present invention, in which an input current to a high frequency heating coil through each matching section is monitored from the matching section side.
2 is a configuration circuit diagram of a matching unit input current detection circuit unit in FIG. 1; FIG.
[3] FIG. 3 (a) is an external view of a high-frequency current detector having a Rogowski type probe for detecting an input current to the matching section, FIG. 3 (b), the use state of the high-frequency current detector FIG.
FIG. 4 is a front view of a crankshaft of a four-cylinder engine.
FIG. 5 is a structural external view showing the connection between each matching section and the high-frequency heating coil.
[Explanation of symbols]
2 high-frequency heating coil groups 2a, 2b, 2c, 2d high-frequency heating coils 3a, 3b, 3c, 3d matching section 5
6 High-frequency oscillator 8 Connection portion 8a, 8b Contact convex portion 8c, 8d Contact concave portion 11a, 11b, 11c, 11d Switching device 20a, 20b, 20c, 20d High-frequency current detector (Rogowski type )
21a, 21b, 21c, 21d Input current signal
22 Rogowski probe
23 Conductive wire
24 Coaxial cable
25 BNC connector
26 Holding member 30 Matching section input current detection circuit section 31 Overcurrent detection circuit 32 Average current detection circuit 33 Current balance detection circuit 34 Overcurrent abnormality detection circuits 41a, 41b, 41c, 41d Input overcurrent signal 42 Average current value signal 43a, 43b, 43c, 43d Unbalance current signal 44a, 44b, 44c, 44d Overcurrent abnormality alarm signal 100 Workpiece (crankshaft)
C Matching capacitor T Disc type transformer

Claims (4)

By high-frequency induction heating coil, when simultaneously high frequency induction heating the plurality of positions of the workpiece as the body to be heated, through the matching portion of the high-frequency oscillator or al multiple, supplies power to each of the high-frequency induction heating coil, the workpiece during high frequency induction heating, detects an input current input to each of the plurality of matching portions,
1) the value of the input current of the plurality to one of the matching portion of the matching portion, whether the overcurrent exceeds a rough or dimethyl set current value, or 2) of the previous SL plurality of matching portions the value of the input current to one of the matching portion of the difference between the average input current value divided by the total number of said plurality of matching portions of the sum of the input current inputted to said plurality of matching portions, Flip or rough When the unbalance current exceeds the set allowable unbalance current value,
A contact failure detection method for a high frequency induction heating coil, wherein a contact failure between the one matching portion and the high frequency induction heating coil connected thereto is detected. The alarm signal for stopping the high frequency induction heating is output to the one matching portion where the contact failure is further detected after the contact failure is detected. Of detecting poor contact of high-frequency induction heating coil.   The contact failure detection method for a high frequency induction heating coil according to claim 1, wherein each of the plurality of matching portions includes a matching capacitor and a disk-type transformer formed in a parallel resonance circuit. The method for detecting contact failure of a high-frequency induction heating coil according to claim 1, wherein an input current input to each of the plurality of matching portions is detected by a Rogowski type current detection means.

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