JP2885511B2 - Apparatus and apparatus for induction hardening machine components with precise power output control - Google Patents

Abstract

An induction hardening machine for contour hardening of machine components such as gears includes a phase angle detector circuit (112) which produces a pulse for each corresponding detection of a predetermined phase angle of an AC signal. A start switch (SW2) and the pulse produced by the phase detector provide inputs to a circuit (116) which requires concurrence of the pulse and activation of the switch before a predetermined width signal pulse is produced. The predetermined width signal pulse activates power switching devices (114) to supply a predetermined power signal to an RF generator (120) coupled to an induction heating coil (128). Precise induction heating is accomplished via precise control of power input to the RF generator (120).

Description

DETAILED DESCRIPTION OF THE INVENTION RELATED APPLICATIONS This application is a pending application Ser. No. 07 / 563,398, filed Aug. 6, 1990, entitled Apparatus an
d Method of Induction-Hardening Machine Component
s With Precise Power Output Control ”.

TECHNICAL FIELD The present invention relates to the technology of induction heating, and more particularly to the use of induction heating devices for case hardening of mechanical components such as gears.

BACKGROUND ART Mechanical components such as gears, splined shaves and sprockets often experience high torque loads, frictional fatigue and impact loads. Gears of this type are typically used in drive trains of power transmissions. An apparatus and method for induction hardening of such machine components is described in U.S. Patent No. 4,845,328 to Storm et al., The contents of which are incorporated herein by reference. Storm et al. And U.S. Patent are both assigned to Contour Hard of Indianapolis, Indiana, U.S.A.
Owned by ening.

As is well known in the art, known devices for the hardening of gear teeth are such that a low frequency current is used to preheat the gear teeth and then a high frequency (radio frequency) current is applied to the gear teeth. Includes a dual frequency device for induction heating used for final heating prior to quench hardening. For the concept of induction hardening of these two frequencies, see the paper "Induction Gear H
ardening by the Dual-Frequency Method "(Heat Tre
ating Magazine, Vol. 19, No. 6, June 1987).

As described in that article, the dual frequency heating method uses both high and low frequency heating sources. The gear is first induction heated with a relatively low frequency source (3-10 KHz) that provides the necessary energy to preheat the entire gear dentition. Immediately following this step, induction heating is followed by a high frequency source typically ranging from 100 to 300 KHz, depending on the size of the gear and the diameter pitch of the gear teeth. The high frequency source heats the contour of the dentition rapidly to the case temperature. Next, the gear is quenched to a predetermined hardness and tempered.

Induction heating is the fastest known method of heating iron alloy gears. In some applications, a low frequency heating process for preheating precedes RF heating for final heating. Heating times for the RF heating step are typically in the range of 0.10 to 2.0 seconds. In induction heating, the gears are mounted on a main shaft and rotated while being placed inside the induction heating coil. A fast pulse of power is supplied to the induction heating coil to obtain optimal final heat of the gear teeth. The workpiece is then manually or automatically transferred to a water quench bath. Since induction hardening imparts the required amount of heat to the component, case hardening requirements and distortion specifications are met with great accuracy.

In induction heating processes, whether dual frequency or single frequency, and regardless of the type of component and its material, the characteristics of the component require an optimal design of both the induction heating coil and the appropriate machine settings. In particular, the number of hours that the high frequency power signal is supplied to the induction heating coil to produce the final heat is the most critical parameter. The exact amount of heat required for gear hardening is directly related to the exact number of hours that the power signal is supplied to the induction heating coil.

Traditionally, two systems are well known in the art for powering induction heating coils as described above. The first system uses what is known in the art as a "solid state" generator method, in which a high power amplifier such as a transistor, which is bipolar or CMOS, supplies a high frequency oscillating signal to an induction heating coil. Used in high frequency RF generators. Another attempt is to use a thyristor-type device that uses a vacuum tube RF generator to turn on and off power to a high frequency, high power vacuum tube oscillator circuit. The output of any of the oscillating circuits is connected to an induction heating coil by a transformer. Some experts in the technology of induction heating coil equipment designed to case harden metal structures have so far favored solid-state RF generators for precise timing control of the power supply to induction heating coils . The tube RF generator is typically a silicon controlled rectifier (SC), also known as a reverse blocking triode thyristor in the JEDEC description
R) receives its input power which is affected by the on / off timing characteristics of the thyristor device, such as R). The power supply timing variations caused by the SCR are inherent in the operation of such devices. In particular, once the SCR is turned "on" for a partial cycle, the anode to cathode terminals remain at a positive voltage even if the on / off signal applied to the gate is removed or deactivated. As long as it is biased, the SCR will continue to conduct current. Even in the worst case of a 60-cycle power signal transmitted by the SCR, half of the 60-cycle waveform is 8.33 milliseconds in a row, resulting in another power signal of 8 milliseconds or more transmitted by the SCR. .

It is recognized that vacuum tube RF generators are preferred by some in induction heating technology because of their characteristic power supply curve when supplying power to the induction heating coil. In addition, because SCRs are devices that select repetitive high-power switching circuits, techniques are needed to accurately control the SCR to provide a specified amount of power to the high-power vacuum tube RF generator.

A method and apparatus for more accurately controlling the timed power output of a silicon controlled rectifier power supply is needed to accurately control the power signal supplied to an induction heating coil used in a case-hardening device. .

SUMMARY OF THE INVENTION An apparatus for induction hardening of machine components with precise control of power output according to the present invention produces an AC power signal
An AC power source, a zero-crossing detector connected to the AC power source for detecting a zero-crossing of the AC power signal and producing a corresponding zero-crossing signal, and a high-frequency high in response to the power input and a signal applied to the power input. A high-frequency generator having an output that produces a power signal, and a high-frequency induction heating coil sized to mate with the gear and connected to the output of the generator, the coil producing a high-frequency electrical signal through the gear;
A thyristor power switching device having a power input and a power output connected to an excitation input and an AC power source;
This power switching device produces an AC power signal at the power output in response to a signal provided to the excitation input, and is connected to the zero crossing detector and the excitation input of the thyristor power switching device to calculate an excitation time and to generate a corresponding excitation signal. To the excitation input, comprising: 1) a device for inputting a predetermined excitation time, and 2) the sum of the excitation time and the delay time corresponds to the minimum integer multiple of the period of the AC power signal. And 3) an input device for receiving a user-supplied manual cycle start input signal, wherein the processor device detects a zero-crossing signal and generates an excitation signal of the AC power signal. The cycle start input signal is delayed by a period equal to the delay time before the excitation signal is applied to the excitation input so that it is deactivated substantially simultaneously with a subsequent zero crossing. Respond to

An induction hardening device according to another aspect of the present invention includes an AC power supply that generates an AC power signal, and a phase detection device that detects a predetermined phase angle of the AC power signal, wherein the detection device has a predetermined phase angle. A high-frequency generator device having a power input that generates a detection signal when a power is input and generates a high-frequency high-power signal at the power output in response to the power input and the power signal applied to the power input; An induction heating coil, the heating coil emitting a high frequency electromagnetic signal in response to the high frequency high power signal, including a power switching device connected to the AC power signal, the power switching device including an excitation input; The power switching device supplies an AC power signal to the power input at the same time as receiving the signal at the excitation input, and provides an excitation signal of a predetermined duration in response to the detection signal. Includes a timer circuit device that supplies the excitation input.

According to another aspect of the present invention, a method for accurately controlling the power supplied to an induction hardening device including an AC power source, a high frequency generator having a power input, and a high frequency induction heating coil is provided by a method comprising: Detecting the predetermined phase angle and connecting an AC power source to the power input of the high frequency generator for a predetermined period in response to the detection of the predetermined phase angle.

According to yet another aspect of the present invention, an induction hardening device for accurately controlling the power supply of a high frequency induction heating coil is provided in response to detecting an AC power source producing an AC power signal and a predetermined phase angle of the AC power signal. A first circuit device for generating a first signal, a switch device for generating a start signal when the switch device is energized, and a predetermined correspondingly responsive to the simultaneous occurrence of the first signal and the start signal. A second circuit arrangement for producing a duration excitation signal; a high frequency generator apparatus having a power input for producing a high frequency high power signal in response to a signal supplied to the power input; a predetermined circuit connected to the AC power signal; A power switching device for providing an AC power signal to the high frequency generator in response to the duration excitation signal.

One object of the present invention is to provide an improved induction hardening machine.

Another object of the present invention is to provide a method for accurately controlling the heating of gears during case hardening by more precisely controlling the power signal supplied to the induction heating coil of the induction hardening machine.

It is another object of the present invention to provide a more accurate high power switching circuit so that the total power output signal can be controlled with greater accuracy.

The above and other objects of the present invention will become more apparent from the following description of preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an exemplary embodiment of an induction hardening system according to the present invention; FIG. 2 is an SCR activity or "on" condition for certain input conditions provided to the SCR gate. FIG. 3 is a graph showing the variation in the power output signal caused by the power switching SCR circuit of the present invention compared to the prior art device. FIG. 4 is another diagram of the induction hardening system according to the present invention. FIG. 4 is a block diagram of an embodiment of FIG.

EXAMPLES For the purpose of promoting an understanding of the principle of the present invention, reference will be made to examples shown in the drawings, and specific terms will be used for the description. However, this is not intended to limit the scope of the invention, and changes and further modifications in the illustrated device,
It will be understood that further applications of the principles of the present invention, as set forth in the examples, will normally occur to those skilled in the art to which the present invention pertains.

Referring now to FIG. 1, there is shown an induction hardening system 10 according to the present invention. Switch SW1 provides an excitation signal to system processor 12 to initiate or initiate gear hardening. The system processor 12 is programmed by the user to control the power signal supplied to the induction heating coil using the timing parameters. Processor 12 provides the on / off power switching signal to power switching SCR circuit 14. System processor 1
2 receives the zero-crossing beacon input signal from the zero-crossing detector 16. One phase b ₁ from the 3b high voltage power supply 18 is provided to the input of the zero crossing detector 16. This 3b high voltage power supply 18
The phase high voltage power is supplied to the power switching SCR circuit 14. When energized, the system processor 12 supplies either a half-wave or a full-wave AC power signal to the primary winding of the boost transformer 22. Transformer 22 boosts AC power signals b ₁ , b ₂ , b ₃ , which are typically 480 volt three-phase signals, to a voltage level at which rectifier and filter 24 produces a 24,000 volt DC signal at its output.

This 24,000 volts at the output of the rectifier filter 24
The DC signal is a power source for a high-energy RF oscillator 26 in the form of a vacuum tube. The output of the high energy RF oscillator 26 is connected via a winding 20 to an induction heating coil 28. Induction heating coil
28 provides a case hardening heating signal to the gear teeth of gear 30 when an RF signal is provided to its input.

Components 22, 24, 26 of system 10 are part of RF generator 20, which is a high frequency, high power RF generator. RF generator 20 falls in McNomonee, Wisconsin, USA
s, Mega Drive N92 W15800 This system is supplied from time to time by Pillar Industries. This RF generator
The 20 is called the "450/600 kW RF generator".

The particular shape and physical attributes of the gear 30 require an exact amount of time that the power switching SCR circuit 14 is turned "on" by the system processor 12 to produce a suitable case-burning result. In some cases, the amount of time that the SCR circuit 14 is turned on is a short period of time, on the order of 0.10 seconds, to obtain the predetermined heating and case-burning of the gear 30. With these conditions in mind, it can be seen why prior art devices that did not include zero-crossing detector 16 could not accurately control the amount of power signal supplied to induction heating coil 28, i.e., total power. You can easily find out.

The system processor 12 of the present invention typically includes a computer with accurate memory and
And a programming input device such as a T / keyboard device. Further, processor 12 has a mass storage device such as a floppy disk drive or hard disk drive used in storing and retrieving control programs. In operation, the operator determines the specific `` on time '' or heating time, which is the exact time at which the power switching SCR circuit 14 must be turned on to provide a fixed amount of high frequency power signal to the induction heating coil 28. Program the system processor 12 via the keyboard. In response to this programmed `` on-time '' information, the system processor 12 activates 8.
Calculate the complement value for a particular "on-time" equal to the difference between "on-times" divided by 33 milliseconds (60 Hz waveform period). The remainder from this calculation is subtracted from 8.33 milliseconds and the processor 12 detects the zero crossing of the 60 Hz signal present at the input of the detector 16 prior to exciting the SCR circuit 14 to power the RF generator. Produces a time value that is the delay time to be delayed. The calculation of this time delay is SC
Is intended to end the on-period or conduction period for R circuit corresponds exactly to the zero crossing or immediately preceding the power signal b ₁ which is fed to the input of the zero crossing detector 16. Thus, the SCR, which remains conductive as long as the anode-to-cathode terminals are forward biased, has signaled the system processor 12 to shut off by deactivating the input to circuit 14 to SCR circuit 14. It does not remain on for a substantial period later.

In the art, the SCR circuit 14 has a half-wave or full-wave
It is well known to provide a b output signal to a transformer 22. If the nature of this signal is half-wave, then the divisor (8.33 ms) is 16.67 ms and the remainder is subtracted from 16.67 ms. In addition, a negative slope zero crossing must be detected to determine an appropriate timing reference point to excite the half-wave output SCR circuit. Thus, the predetermined "on-time" is divided by 16.67, and the remainder is subtracted from 16.67. The result of this subtraction process is the delay period required after the negative slope zero crossing of the power signal prior to exciting the SCR circuit 14 to produce a half-wave output. SCR
Although the other phases of circuit 14 (b ₂ and b ₃ ) each remain “on” even after the input to circuit 14 is de-energized, the above approach provides accurate and repeatable power output from SCR circuit 14. Is generated.

Next, in FIG. 2, the SCR for a certain gate signal condition
A timing diagram showing the change in the active or "on" state of the device is shown. Curve 40 is a standard sine wave power signal representing the b ₁ signal at the input of the detector 16. Curve 40 is a 60 horizontal signal plotted against time. Curves 42, 46 represent the signals generated by system processor 12 and provided to the gate input of SCR circuit 14. Curves 42, 46 are the "on times" required to produce a predetermined amount of heat in a particular gear 30 to be induction hardened.

The circuit 14 is provided with a power signal to the excitation or generator 20 at a point in time during the off / on transition of the curve 42. At the end i.e. time T _D of the "on-time" of the curve 42, the signal changes from "ON" state to the "off" state. The exact timing of the on / off transient does not occur near the zero crossing of curve 40. Since the excitation signal represented by curve 42 does not return to the "off" state until after the zero crossing at time T _C, is applied to the RF generator 20, the power signal represented by curve 44, curve 42
On / off up to 8.33 milliseconds time T _C, which can also be a even after the transient state is continuously "on" state. Thus, if the on signal generated by the system processor 12 begins at time T _B and continues until time T _D , the total power signal supplied to the RF generator will be equal to time T _B until time T _E in the graph.
It will continue during the entire period T ₂ from.

To accurately control the power supplied to the induction heating coil, and thereby to obtain more precise control of the induction hardening process, the system according to the present invention provides a system in which the SCR excitation signal represented by curve 46 has a zero crossing of curve 40. Alternatively, the time delay beyond the zero crossing (in this example, the zero crossing at T _O ) is calculated to turn on the SCR circuit 14 so as to change from the “on” state to the “off” state immediately before. For example, the power signal is compared to the gate-on time input signal represented by curve 42 which switches the SCR circuit.
To remove the 44 other "on-times", the system processor 12 determines the predetermined "on-time" T ₁ divided by 8.33 ms.
Corresponding calculated time T ₃ and produces a time T ₃ by subtracting the remainder from 8.33 milliseconds. Then, the system processor, the curve 42 as "on-time", "off" from the "on" state at the zero crossing and the corresponding time T _C of the curve 40 exactly equal excitation curve 46 the power signal for a duration state so as to change the delays the excitation of the SCR circuit 14 for a period T ₃ after a zero crossing.

Because curve 46 is a very closely related to the zero crossing at time T _C, the exact "on-time" of the SCR circuit 14 weight obtained, thereby accurately by precision power that has not been known heretofore in the SCR circuit Control. At this time, the induction heating coil 28
Is precisely controlled. For this reason, a vacuum tube type RF generator, which is preferred by those skilled in the art as being superior to a solid-state semiconductor type high frequency RF generator, is required to provide an accurate power signal quality and an induction heating coil 28.
Can be used to produce the same accurate quality given to

Although only one phase (b ₁ ) of the power supply 18 is shown in FIG. 2, those skilled in the art will appreciate that in a 3b system, all three phases are 120 °.
It will be clear that this is relevant. This results in a fixed amount of another power signal being supplied by the other phases (b ₂ and b ₃ ) of the power supply 18 beyond the time T _C by the excitation signal represented by the curve 46. Nevertheless, the deactivation signal occurs at another power phase, so that the other power provided by the other two phases is of constant quality. Thus, the amount of power provided by the system 10 to the gear 30 may be repeated by establishing a fixed timing reference point (for one phase) at which to turn the 3b power on / off.

3, a graph of the power output of the RF generator 20 is shown. Generator indicated by curve 50
The 20 maximum power outputs can be adjusted vertically to obtain higher or lower total instantaneous power outputs. SC
Variations in "on time" indicated by the time T ₁ and T ₂ as a result of the inherent functionality of the R circuit is shown at the bottom of the graph. T _{1 when the} SCR circuit is at a given “on time”
If maintaining the ON state by the length of the opposed time T ₂ are the partial another power represented by the portion 52 multiplied by the hatch below the curve 50, which is not applied to hatch under the curve 50 in addition to the actual predetermined power to extend until the end of time T ₁ is represented by, it is supplied to the induction heating coil 29.
Another amount of power supplied to induction heating coil 28 causes excessive heating of gear 30.

As shown in the graph of FIG. 3, in particular "on-time" T ₁
When is approximately 0.10 seconds, it approaches larger fluctuations in the case-burning process. The maximum difference between times T ₂ and T ₁ 8.33
The power represented by region 52 can represent as much as 8-10% power difference when a power signal of 0.10 seconds is required for induction heating coil 28. Another recognized fact is that once the gear 30 is heated, the heat transfer properties of the gear are not linear, and once the gear is heated at the periphery, heat is conducted further deeper to the gear face, thus reducing the area. The extra heating time represented by 52 can significantly increase the gear heat. For this reason, it is highly desirable to control the power supplied to the induction heating coil 28 in the manner described above.

Referring now to FIG. 4, another embodiment of the induction hardening system 110 according to the present invention is shown. Switch SW2 provides a reset / start signal to single pulse timer circuit 116. AC power supply 118 provides an AC signal to phase angle detector 112 and power switching device 114. Phase angle detector 1
12 provides a series of pulses to the input of a single pulse timer circuit 116. Each pulse from detector 112 corresponds to the detection of a predetermined phase angle of the AC power signal from power supply 118.
Upon receipt of the reset / start signal from switch SW2, single pulse timer circuit 116 is triggered by the next pulse from detector 112 to produce a pulse or signal having a predetermined duration. Pulses of a predetermined duration are used for power switching devices.
Enable 114. Therefore, the start of the heating cycle as a result of the closing of switch SW2 is delayed until a predetermined phase angle is detected by phase angle detector 112. Phase angle detector 112 provides a phase detection device that detects a predetermined phase angle in a power signal from AC power supply 118.

As in the previous embodiment, RF generator 120 receives a power signal from power switching device 114,
In response, a high frequency high power signal is supplied to induction heating coil 128 via winding 129. Winding 129 creates an impedance balance between the output of RF generator 120 and induction heating coil 128. Single-phase and multi-phase power supplies are conceivable.

The phase angle detector 112 is implemented using a triac phase angle controller part number TDA1185A manufactured by Motorola of Phoenix, USA. The TDA1185A device is programmable to produce an output signal corresponding to the detection of a predetermined phase angle of the AC signal. This predetermined phase angle can be changed by the TDA1185A device according to an externally set voltage representing a predetermined conduction angle. (See discussion of control signals below.) Because the TDA1185A device detects the firing angle in the negative half of the AC signal,
Even if the firing angle in the negative half of the AC signal is required,
An inverting operational amplifier is inserted between the AC power supply and the phase angle detector 112 to invert the AC signal, thereby providing an input signal to the phase angle detector 112 such that excitation in the negative half of the AC signal occurs.

Signal pulse timer circuit 116 is available from Texas Instruments.
It is implemented using a re-triggerable monostable multivibrator integrated circuit, part number 74LS123, manufactured by the Company. This 74LS1
23 is a rising edge triggered device, so that the pulse generated by the phase angle detector 112 can be used to trigger an output pulse from the timer circuit 116. The signal generated by switch SW2 can be retriggered, enabled, or rearmed.
ng) The signal is supplied to the timer circuit 116. One 74LS123 device
The combination of phase angle detector 112 and timer circuit 116 can be configured to produce output pulses from sub-milliseconds to very large durations, such as time units.
It provides a widely variable control of the timing function required to excite the power switching device 114 in accordance with the previously described conditions that require the supply of a specific duration power signal to the RF generator 120.

Optional control signals, represented by dashed lines 132, 134, detect the duration signal of the selected phase angle and pulse width.
112 and circuit 116, respectively. In particular, the signal path
The phase angle control signal present at 134 and supplied to the input of the detector 112 provides phase angle selection information to the detector 112. Signal path 1
In response to the signal at 34, detector 112 produces an output pulse that corresponds in time with the occurrence of the predetermined phase angle established by the signal on signal path 134. Similarly, signal path 13
The duration control signal present at 2 controls the duration of the pulse generated by the circuit 116. The signal in signal path 132 typically comprises a potentiometer / capacitor combination that establishes an attenuated signal, as is known in such circuits.

4 includes several components that are the same as those of device 10 of FIG. In particular, the AC power supply 118 is compatible with the three-phase high voltage power supply 18 and is a power switching device.
114 corresponds to the power switching SCR circuit 14, RF generator 120 corresponds to the RF generator 20, and induction heating coil 1
28 corresponds to the induction heating coil 28, and the gear 130 corresponds to the gear 30. Triac or silicon controlled rectifier (SC
R) is considered the power switching device in block 114.

In operation, pulses occurring at the output of the phase angle detector 112, the phase angle and temporally correspond to predetermined of the AC signal indicated by time line T _B in FIG. Similarly, the output pulse produced by timer circuit 116 corresponds to the time T _2. This ensures accurate timing and power output control
The difficulty of exciting the AC power supply is overcome by the embodiment of FIG. 1 used to determine the on-time of the power signal using the time delay after the zero crossing, or as in the embodiment of FIG. A particular phase angle is detected to determine when the excitation signal is required for excitation of the power switching device. According to both embodiments of the present invention, the predetermined timing reference point for the AC power signal is such that the power switching device is off at a precise predetermined time, typically at a zero crossing as in most thyristors. Prior to the excitation of the power switching device to produce an excitation signal that falls before or at the same time as the subsequent zero crossing of the power signal so that
The AC power signal is found or detected.

Alternatively, the phase angle detector 112 and the timer circuit 1
16 is part of a microcomputer-based controller (not shown), which uses an A / D converter (not shown) to monitor the amplitude (corresponding to the phase angle) of the signal from the power supply 118 It is also possible. Still further, user-modifiable software allows control of the detected predetermined phase angle and the control pulse width provided to power switching device 114.

Although the present invention has been shown and described in detail in the drawings and text, it should be understood that this embodiment is illustrative and is not limiting in nature, and that only preferred embodiments have been shown and described; It will be understood that all changes and modifications equivalent to the spirit of the invention are required to be protected.

(56) References JP-A-58-103880 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C21D 1 / 10,1 / 42 H05B 6/10

Claims (5)

(57) [Claims] An AC power supply for producing an AC power signal; zero-crossing detector means connected to the AC power supply for detecting zero-crossings of the AC power signal and generating a corresponding zero-crossing signal; A high frequency generator having an output and producing a high frequency high power signal in response to a signal provided to the power input; sized to match the gear and connected to the output of the generator, A high frequency induction heating coil for generating a high frequency electrical signal passing therethrough, an excitation input, a power input connected to the AC power source, and a power output, wherein the AC power signal is responsive to a signal supplied to the excitation input. To the power input of the high frequency generator, to the thyristor power switching means, to the zero crossing detector means and to the excitation input of the thyristor power switching means. Processor means for calculating an excitation time and providing an excitation signal corresponding to the excitation input, the processor means comprising: (a) means for inputting a desired excitation time; and (b) excitation time. Means for controlling the delay time such that the sum of the delay time and the delay time corresponds to a minimum integer multiple of the period of the AC power signal; and (c) means for receiving a user-supplied manual cycle start input signal. The processor means is responsive to a cycle start input signal by detecting a zero crossing signal, and the excitation signal is applied to the excitation input such that the excitation signal is extinguished substantially simultaneously with a subsequent zero crossing of the AC power signal. An induction quenching machine for gear quenching, characterized in that a period equal to the delay time is delayed before feeding. 2. A thyristor power switching means having an AC power supply, an excitation input for generating a power signal in response to a signal appearing on the excitation input, and an RF for generating a high frequency, high power signal in response to the power signal. A method for accurately controlling heating of a gear from an induction quenching device including a generator and an induction heating coil connected to the RF generator and generating an electrical signal on the gear in response to the high frequency, high power signal. Determining a desired excitation time to supply power to the heating coil based on the shape of the gear; anddividing the desired excitation time by half the period of the AC power supply signal to generate a remainder. Subtracting the remainder from half of the period of the AC power supply signal to generate a delay time, and performing the excitation after a time equal to the delay time has been spent. During the corresponding period, the thyristor power method for accurately controlling and supplying an excitation signal to the excitation input, the heating of the gear from the induction hardening apparatus comprising a switching means. 3. A low-frequency AC power supply for generating a low-frequency AC power signal; and phase detecting means for detecting a predetermined phase angle of the low-frequency AC power signal, wherein the detecting means detects the predetermined phase angle. A high frequency generator having a power input and a power output, wherein the high frequency generator generates a high frequency high power signal at the power output in response to a power signal applied to the power input; A high frequency induction heating coil connected to and emitting a high frequency electromagnetic wave signal in response to the high frequency high power signal; connected to the AC power source and including an excitation input; and receiving the signal at the excitation input; Power switching means for supplying an AC power signal to the power input; and timer circuit means for responsive to the detection signal for providing an excitation signal contained in a single predetermined duration pulse to the excitation input. , Induction hardening apparatus characterized by comprising provided. 4. A low-frequency generator for generating a low-frequency AC power signal at an output.
An AC power supply, a high-frequency generator having a power input, and a method for accurately controlling power supplied to an induction heating device including a high-frequency induction heating coil, wherein a predetermined phase angle of the low-frequency AC power signal is detected. And the AC power output in response to the detection of the predetermined phase angle.
Connecting to the power input of the high frequency generator for a single predetermined duration; and a method for accurately controlling the power supplied to the induction heating device. 5. An AC power supply for generating a low-frequency AC power signal; a first circuit for generating a first signal in response to detection of a predetermined phase angle of the low-frequency AC power signal; The switch means for generating a start signal when the first signal is generated and a second continuous pulsing excitation signal responsive to the simultaneous occurrence of the first signal and the start signal to produce a single continuous predetermined sustained pulse excitation signal responsive thereto. A circuit means having a power input and generating a high frequency high power signal in response to a signal applied to the power input; and a single continuous predetermined power supply connected to the AC power source. Power switching means for supplying the low frequency AC power signal to the high frequency generator in response to a sustained pulse excitation signal; a high frequency quenching device for accurately controlling the power supply of the high frequency induction heating coil. Place.