U.S. patent application number 13/256120 was filed with the patent office on 2012-04-26 for induction hardening control system.
This patent application is currently assigned to NETUREN CO., LTD.. Invention is credited to Ken-ichi Hoshiba, Fumiaki Ikuta, Keisuke Ito, Taichi Kitamura, Tetsuya Ono, Yue Yang.
Application Number | 20120097663 13/256120 |
Document ID | / |
Family ID | 42727957 |
Filed Date | 2012-04-26 |
United States Patent
Application |
20120097663 |
Kind Code |
A1 |
Ito; Keisuke ; et
al. |
April 26, 2012 |
INDUCTION HARDENING CONTROL SYSTEM
Abstract
The present invention includes: a hardening control unit (70)
for controlling an induction hardening apparatus (10, 10A) based on
setup conditions data regarding the induction hardening apparatus
(10, 10A); a hardening monitoring unit (20) that measures, as
measurement data, the electric quantity in an electric circuit
configured to include a high-frequency inverter (11), a capacitor
(12), and a heating coil (14, 14A, 14B) and that monitors an
induction hardening status; and a data collecting unit (80) that
collects the data from various sensors in the induction hardening
apparatus (10, 10A, 10B) obtained when the induction hardening
apparatus (10) subjects the work (15, 15A, 15B) to an induction
hardening based on the setup conditions data outputted from the
hardening control unit (70) and that collects the measurement data
from the hardening monitoring unit (20) to store the collected data
from the various sensors and the measurement data so that the
collected data from the various sensors and the measurement data
are associated to each other.
Inventors: |
Ito; Keisuke; (Kanagawa,
JP) ; Yang; Yue; (Indianapolis, IN) ; Ikuta;
Fumiaki; (Kanagawa, JP) ; Kitamura; Taichi;
(Aichi, JP) ; Ono; Tetsuya; (Kanagawa, JP)
; Hoshiba; Ken-ichi; (Kanagawa, JP) |
Assignee: |
NETUREN CO., LTD.
Tokyo
JP
|
Family ID: |
42727957 |
Appl. No.: |
13/256120 |
Filed: |
March 12, 2009 |
PCT Filed: |
March 12, 2009 |
PCT NO: |
PCT/JP2009/054817 |
371 Date: |
December 14, 2011 |
Current U.S.
Class: |
219/602 |
Current CPC
Class: |
Y02P 10/253 20151101;
H05B 6/06 20130101; C21D 11/00 20130101; Y02P 10/25 20151101; C21D
1/10 20130101; C21D 1/42 20130101 |
Class at
Publication: |
219/602 |
International
Class: |
H05B 6/10 20060101
H05B006/10 |
Claims
1. An induction hardening control system that is connected to an
induction hardening apparatus configured so that a high-frequency
inverter is connected to a capacitor and a heating coil and that
controls an induction hardening to a work placed in the vicinity of
a heating coil, comprising: a hardening control unit that controls
the induction hardening apparatus based on setup conditions data
regarding the induction hardening apparatus; a hardening monitoring
unit that measures, as measurement data, an electric quantity in an
electric circuit configured to include a high-frequency inverter, a
capacitor, and a heating coil to monitor an induction hardening
status; and a data collecting unit that collects data from various
sensors in the induction hardening apparatus obtained when the work
is subjected to the induction hardening by the induction hardening
apparatus based on the setup conditions data outputted from the
hardening control unit and that collects the measurement data from
the hardening monitoring unit to store the collected data from the
various sensors and the measurement data so that the collected data
from the various sensors and the measurement data are associated to
each other.
2. The induction hardening control system according to claim 1,
wherein the measurement data includes output current from the
high-frequency inverter and a voltage generated in the heating
coil.
3. The induction hardening control system according to claim 1,
wherein the measurement data includes a load impedance calculated
based on output current from the high-frequency inverter and a
voltage generated in the heating coil.
4. The induction hardening control system according to claim 1 or
2, wherein the hardening monitoring unit calculates an effective
value based on the output current from the high-frequency inverter
and calculates an effective value based on the voltage generated in
the heating coil to thereby monitor an induction hardening
processing based on the respective calculated effective values.
5. The induction hardening control system according to claim 1 or
3, wherein the hardening monitoring unit calculates an effective
value based on the output current from the high-frequency and
calculates an effective value based on the voltage generated in the
heating coil to thereby calculate a load impedance based on the
respective calculated effective values.
6. The induction hardening control system according to claim 1,
wherein the hardening monitoring unit and the hardening control
unit are mutually connected via a communication means.
7. The induction hardening control system according to claim 1,
wherein the data collecting unit is connected to the hardening
monitoring unit and/or the hardening control unit via a
communication means.
Description
[0001] The present invention relates to an induction hardening
control system ensuring whether an induction hardening to a work is
performed in accordance with pre-determined setup conditions.
BACKGROUND ART
[0002] In order to improve the property of a work such as hardness,
the work is subjected to a hardening processing by high-frequency
power. FIG. 29 is an appearance diagram schematically illustrating
a general hardening processing. For example, a work 50 to be heated
is configured, as shown, to have an extension portion 52 at a
bar-like base portion 51 in a coaxial manner. Thus, the bar-like
base portion 51 and the extension portion 52 form a substantially
L-like cross section. A heating coil 61 is a saddle-type coil. The
heating coil 61 is adapted to connect both ends of a semicircular
portion 61a with a pair of straight portions 61b, 61b. In order to
perform a hardening processing, a retention means which is not
shown is firstly allowed to retain the work 50. Then, the heating
coil 61 is placed over the work 50 so that the semicircular portion
61a of the heating coil 61 is positioned at the upper face-side of
the extension portion 52 and the straight portion 61b of the
heating coil 61 is positioned to be parallel with a bar-like base
portion 51. In this arrangement, whether the distance between the
heating coil 61 and the extension portion 52 is within a
predetermined range or not is confirmed. Thereafter, while the work
50 is being rotated, high-frequency power is inputted from a
high-frequency inverter 62 to the heating coil 61, thereby
subjecting the work to a hardening processing. The reference
numeral 63 in the drawing denotes a matching capacitor constituting
a parallel resonance circuit with the heating coil 61.
[0003] A known induction hardening apparatus used in a hardening
processing has an equivalent circuit configuration in which output
terminals of a high-frequency inverter have therebetween a matching
capacitor and a heating coil that are connected in parallel. In
order to assure the hardening quality, it is ideal that the
effective power (kW) inputted to the heating coil is preferably
actually measured for the control based on this effective power as
a reference. The equivalent circuit of a heating coil is
represented by a serial connection of inductance and resistance.
Furthermore, the work heated by the heating coil functions as a
resistance load. A method of monitoring the effective power is a
method to measure the phase difference between the voltage (Vcoil)
generated at both ends of the heating coil and the coil current
(Icoil) flowing in the heating coil to calculate the effective
power based on the formula Pkw=cos .PHI.VcoilIcoil. In the formula,
cos .PHI. represents a power factor (.PHI. represents a power
factor angle).
[0004] However, in the case of an induction hardening, many loads
have a low power factor and the phase difference between the coil
voltage and the coil current as a measurement target is high.
Specifically, a parallel circuit of a capacitor and a heating coil
has Q of about 10. The power factor may be assumed as a reciprocal
number of Q. When Q is 10, the power factor is 0.1 and the power
factor angle .phi. is 84 degrees. Thus, the resultant effective
power is small that is calculated by measuring Vcoil and Icoil to
integrate these values by an arithmetic circuit. Since this
arithmetic circuit is easily influenced by the temperature drift
and the fluctuation of a frequency and a phase difference, the
current situation is that the effective power of the induction
hardening processing cannot be accurately monitored based on the
calculation value by the arithmetic circuit. [0005] Patent Document
1: Japanese Published Unexamined Patent Application No. 2002-317224
[0006] Patent Document 2: Japanese Published Unexamined Patent
Application No. 2000-150126 [0007] Patent Document 3: Japanese
Published Unexamined Patent Application No. 2003-231923
DISCLOSURE OF INVENTION
Problems to be Solved by the Invention
[0008] In view of the above, when an output control is performed so
as to provide a constant output voltage from a high-frequency
oscillator, a conventional method has been considered to detect the
current of a heating coil to calculate an average current for power
monitoring (e.g., Patent Document 1). However, the coil current, to
be exact, has an inductance component of the coil and a resistance
component. Thus, even when the load fluctuates, the coil current
has a small fluctuation, thus causing a low sensitivity. This
consequently prevents an effective power monitoring.
[0009] Another conventional method has been considered to perform
the monitoring by detecting an output voltage and output current
from the high-frequency inverter or by detecting the output power
(e.g., Patent Documents 2 and 3). This detection of the output
power includes the detection of an output voltage and output
current to multiply the effective values thereof. However, this
method is to monitor the output power from the high-frequency
inverter, i.e., effective power inputted to the load when seen from
between the output terminals of the high-frequency inverter. Thus,
this method is influenced by the loss in a matching circuit and the
power transmission loss. This method cannot sensitively detect the
load fluctuation and has a low sensitivity. When a distance from
the high-frequency inverter to the heating coil is long in
particular, the power transmission loss causes a decreased
sensitivity at which the load fluctuation is detected.
[0010] On the other hand, when the positional relation between the
work as a hardening target and the heating coil deviates from a
predetermined range, another disadvantage is caused, that is, the
load fluctuation generates to prevent an appropriate hardening
processing. This will be described specifically below. In the
hardening processing shown in FIG. 29, the work 50 does not always
have an identical size and has a size within a certain allowable
range. Thus, there is a possibility where the positional relation
between the work 50 and the heating coil 61 may be different
depending on every work. In spite of this, an appropriate hardening
processing is not assured even when the same high-frequency power
is inputted regardless of the work 50. Specifically, as to the
positional relation between the work 50 and the heating coil 61,
when the gap between the work 50 and the heating coil 61 increases,
that is, when the distance between the upper face 53 of the
extension portion 52 and the semicircular portion 61a of the
heating coil 61 increases, it is hard to input a high frequency
wave to the work 50. This causes a current situation where every
work cannot have an assured hardening processing quality.
[0011] The quality control of induction hardening processing for
each work is altered not only by the circuit between high-frequency
inverter and heating coil but also by concentration or temperature
of hardening liquid. Further, it is impossible to check if
hardening is processed in accordance with the predetermined setup
conditions for each work.
[0012] In view of the above problems, it is an objective of the
present invention to provide an induction hardening control system
ensuring whether an induction hardening to a work is processed in
accordance with the setup conditions.
Means for Solving the Problems
[0013] In order to achieve the above objective, the present
invention provides an induction hardening control system that is
connected to an induction hardening apparatus configured so that a
high-frequency inverter is connected to a capacitor and a heating
coil and that controls an induction hardening to a work placed in
the vicinity of a heating coil. The system includes: a hardening
control unit that controls the induction hardening apparatus based
on setup conditions data regarding the induction hardening
apparatus; a hardening monitoring unit that measures, as
measurement data, an electric quantity in an electric circuit
configured to include a high-frequency inverter, a capacitor, and a
heating coil to monitor an induction hardening status; and a data
collecting unit that collects data from various sensors in the
induction hardening apparatus obtained when the work is subjected
to the induction hardening by the induction hardening apparatus
based on the setup conditions data outputted from the hardening
control unit and that collects the measurement data from the
hardening monitoring unit to store the collected data from the
various sensors and the measurement data so that the collected data
from the various sensors and the measurement data are associated to
each other.
[0014] In the above configuration, the measurement data preferably
includes output current from the high-frequency inverter and a
voltage generated in the heating coil.
[0015] In the above configuration, the measurement data may include
a load impedance calculated based on the output current from the
high-frequency inverter and the voltage generated in the heating
coil.
[0016] In the above configuration, the hardening monitoring unit
preferably calculates an effective value based on the output
current from the high-frequency inverter and calculates an
effective value based on the voltage generated in the heating coil
to thereby monitor an induction hardening processing based on the
respective calculated effective values.
[0017] In the above configuration, the hardening monitoring unit
may calculate the effective value based on the output current from
the high-frequency inverter and may calculate the effective value
based on the voltage generated in the heating coil to thereby
calculate the load impedance based on the respective calculated
effective values.
[0018] In the above configuration, the hardening monitoring unit
and the hardening control unit are preferably mutually connected
via a communication means.
[0019] In the above configuration, the data collecting unit is
preferably connected to the hardening monitoring unit and/or the
hardening control unit via the communication means.
Effects of the Invention
[0020] According to the present invention, the high-frequency
inverter is output-controlled by the hardening control unit based
on the setup conditions data. During this, the hardening monitoring
unit measures the electric quantity in the electric circuit
composed of the high-frequency inverter, the capacitor, and the
heating coil. The data collecting unit collects the data from
various sensors in the induction hardening apparatus obtained by
the induction hardening of the work by the induction hardening
apparatus based on the setup conditions data outputted from the
hardening control unit and the measurement data by the hardening
monitoring unit. Thus, by comparing these pieces of collected data
with induction hardening conditions to the respective works,
whether the induction hardening is performed appropriately or not
can be confirmed easily.
BRIEF DESCRIPTION OF DRAWINGS
[0021] FIG. 1 is a configuration diagram of an induction hardening
control system according to the first embodiment of the present
invention.
[0022] FIG. 2 is a diagram schematically showing a part of an
induction hardening monitoring apparatus in the induction hardening
control system shown in FIG. 1.
[0023] FIG. 3 is a configuration diagram showing an internal
configuration of induction hardening monitoring unit, particularly
including its detail, in the induction hardening control system
shown in FIG. 1.
[0024] FIG. 4 shows a voltage measurement circuit in a signal
processing unit in FIG. 3.
[0025] FIG. 5(A) shows a load resonance circuit. FIG. 5(B) is an
equivalent circuit diagram of the load resonance circuit shown in
FIG. 5(A) when the frequency of the high-frequency inverter is
synchronized with the resonance frequency of the load resonance
circuit.
[0026] FIG. 6 is a schematic circuit diagram for explaining the
reason why a coil gap fluctuation can be observed as a load
impedance fluctuation. FIG. 6(A) is an equivalent circuit diagram
of a modeled induction heating. FIG. 6(B) is an equivalent circuit
diagram when no work exists. FIG. 6(C) is a diagram illustrating an
equivalent circuit of FIG. 4(B) with a parallel circuit.
[0027] FIG. 7 is a schematic diagram for explaining a modification
example of the second embodiment of the present invention.
[0028] FIG. 8 shows the result of Example 1 in the first embodiment
of the present invention. FIG. 8(A) shows a signal waveform
corresponding to the voltage in the heating coil. FIG. 8(B) shows a
signal waveform corresponding to the output current from the
high-frequency inverter.
[0029] FIG. 9 shows the result of Example 2 in the first embodiment
of the present invention. FIG. 9(A) shows a signal waveform
corresponding to the voltage in the heating coil. FIG. 9(B) shows a
signal waveform corresponding to the output current from the
high-frequency inverter.
[0030] FIG. 10 shows the result of example 3 in the first
embodiment of the present invention. FIG. 10(A) shows a signal
waveform corresponding to the voltage in the heating coil. FIG.
10(B) shows a signal waveform corresponding to the output current
from the high-frequency inverter.
[0031] FIG. 11 shows the result of Comparison Example 1 in the
first embodiment of the present invention. FIG. 11(A) shows a
signal waveform corresponding to the voltage in the heating coil.
FIG. 11(B) shows a signal waveform corresponding to the current of
the primary-side of the current transformer shown in FIG. 3.
[0032] FIG. 12 shows the result of Comparison Example 2 in the
first embodiment of the present invention. FIG. 12(A) shows a
signal waveform corresponding to the voltage in the heating coil.
FIG. 12(B) shows a signal waveform corresponding to the current of
the primary-side of the current transformer shown in FIG. 3.
[0033] FIG. 13 is a diagram showing the positional relation between
the heating coil and the work according to Example 4 in the second
embodiment of the present invention
[0034] FIG. 14 is a diagram showing the coil gap dependency of the
load impedance in the result of Example 4 in the second embodiment
of the present invention.
[0035] FIG. 15 is a diagram showing the coil gap dependency to the
load impedance change rate in the result of Example 4 in the second
embodiment of the present invention.
[0036] FIG. 16 is a diagram showing the coil gap dependency of the
output current from the high-frequency inverter in the result of
Example 4 in the second embodiment of the present invention.
[0037] FIG. 17 is a diagram showing the coil gap dependency of the
change rate of the output current from the high-frequency inverter
in the result of Example 4 in the second embodiment of the present
invention.
[0038] FIG. 18 shows waveforms when the coil gap d is 1.5 mm in the
result of Example 4 in the second embodiment of the present
invention. FIG. 18(A) is a diagram showing a waveform of the load
impedance. FIG. 18(B) is a diagram showing a waveform of the output
current.
[0039] FIG. 19 shows waveforms when the coil gap d is 2.1 mm in the
result of Example 4 in the second embodiment of the present
invention. FIG. 19(A) is a diagram showing a waveform of the load
impedance. FIG. 19(B) is a diagram showing a waveform of the output
current.
[0040] FIG. 20 is a diagram showing the coil gap dependency of the
coil voltage in the result of Comparison Example 3 in the second
embodiment of the present invention.
[0041] FIG. 21 is a diagram showing the coil gap dependency on the
change rate of the coil voltage in the result of Comparison Example
3 in the second embodiment of the present invention.
[0042] FIG. 22 is a diagram showing the coil gap dependency of the
output current from the high-frequency inverter in the result of
Comparison Example 3 in the second embodiment of the present
invention.
[0043] FIG. 23 is a diagram showing the coil gap dependency of the
change rate of the output current from the high-frequency inverter
in the result of Comparison Example 3 in the second embodiment of
the present invention.
[0044] FIG. 24 shows waveforms when the coil gap d is 1.5 min in
the result of Comparison Example 3 in the second embodiment of the
present invention. FIG. 24(A) is a diagram showing the waveform of
the coil voltage. FIG. 24(B) is a diagram showing the waveform of
the output current.
[0045] FIG. 25 shows waveforms when the coil gap d is 2.1 mm in the
result of Comparison Example 3 in the second embodiment of the
present invention. FIG. 25(A) is a diagram showing the waveform of
the coil voltage. FIG. 25(B) is a diagram showing the waveform of
the output current.
[0046] FIG. 26 is a configuration diagram of an induction hardening
control system according to the first modification example
different from the diagram shown in the FIG. 1.
[0047] FIG. 27 is a configuration diagram of an induction hardening
control system according to the second modification example
different from the diagram shown in the FIG. 1.
[0048] FIG. 28 is a configuration diagram of an induction hardening
control system according to the third modification example
different from the diagram shown in the FIG. 1.
[0049] FIG. 29 is a diagram schematically showing a general
hardening processing.
EXPLANATION OF REFERENCE NUMERALS
[0050] 1,2,3, and 4: Induction hardening control system [0051] 3A,
3B, and 3C: Induction hardening system [0052] 10, and 10A:
Induction hardening apparatus [0053] 11: High-frequency inverter
[0054] 11a: Sensor [0055] 12: Matching capacitor [0056] 13, 13A,
and 13b: Current transformer [0057] 13a: Primary current-side coil
[0058] 13b: Secondary current-side coil [0059] 14, 14A, 14B, and
61: Heating coil [0060] 15, 15A, and 15B Work (to-be-heated object)
[0061] 16,16a,16b: Switcher [0062] 20: Hardening monitoring unit
[0063] 21: Current sensor [0064] 22, 22A, 22B: Voltage sensor
[0065] 22a, 22b, 22c, and 22d: End portion of voltage sensor [0066]
23: Control unit [0067] 23a: Current detection unit [0068] 23b:
Voltage detection unit [0069] 23c: Signal processing unit [0070]
23d: Determination unit [0071] 23e: Display unit [0072] 24: Warning
unit [0073] 30: Voltage measurement circuit [0074] 31: First
operational amplifier [0075] 32: Second operational amplifier
[0076] 33: Filter circuit [0077] 34: Input resistance [0078] 35:
First diode [0079] 36: Second diode [0080] 37, 38, 39, 40, and 41:
Resistance [0081] 42: Capacitor [0082] 50: Work [0083] 51: Bar-like
base portion [0084] 52: Extension portion [0085] 53: Upper face
[0086] 61a: Semicircular portion [0087] 61b: Straight portion
[0088] 70: Hardening control unit [0089] 71: Input unit [0090] 71:
Memory unit [0091] 73: Output unit [0092] 74: Input and output
control unit [0093] 80: Data collecting unit [0094] 90: Data
editing unit [0095] 100: First cooling system [0096] 101: Coolant
tank [0097] 102: Flow sensor [0098] 102, and 115 Flow sensor [0099]
103 and 114: Pump [0100] 110: Second cooling system [0101] 111:
Jacket [0102] 112: Retrieving unit [0103] 113: Tank [0104] 113a:
Heating unit [0105] 116: Temperature sensor [0106] 117: Measuring
unit
BEST MODES FOR CARRYING OUT THE INVENTION
[0107] The following section will describe some embodiments of the
present invention with reference to the attached drawings.
First Embodiment
[0108] FIG. 1 is a configuration diagram illustrating an induction
hardening control system according to the first embodiment of the
present invention. FIG. 2 is a schematic view illustrating a part
of an induction hardening apparatus in the induction hardening
control system shown in FIG. 1. FIG. 3 is a configuration diagram
particularly illustrating the details of the internal configuration
of the hardening monitoring unit in the induction hardening control
system shown in FIG. 1.
[0109] An induction hardening control system 1 includes: an
induction hardening apparatus 10 that has a high-frequency inverter
11, a capacitor 12, and a heating coil 14 for example; a hardening
control unit 70 that controls the high-frequency inverter based on
setup conditions data; a hardening monitoring unit 20 that
measures, as measurement data, the electric quantity in an electric
circuit in the induction hardening apparatus 10 and that monitors
the induction hardening; a data collecting unit 80 that collects
data from various sensors in the induction hardening apparatus 10
obtained when the work 15 is subjected to the induction hardening
by the induction hardening apparatus 10 based on the setup
conditions data outputted from the hardening control unit 70 and
that collects the measurement data from the hardening monitoring
unit 20 to store the collected data from the various sensors and
the measurement data so that the collected data from the various
sensors and the measurement data are associated to each other; and
a data editing unit 90 that obtains, from the data collecting unit
80, the data from the various sensors and the measurement data to
edit these pieces of data. The data collecting unit 80 also may
collect the setup conditions data from the hardening control unit
70 so that the setup conditions data is stored as a pair with the
above-described data from the various sensors and measurement
data.
[0110] As shown in FIGS. 1 and 2, the induction hardening apparatus
10 has an electric circuit configuration composed of a
high-frequency inverter 11, a matching capacitor 12 connected
between the output terminals of the high-frequency inverter 11,
especially between output cables, a heating coil 14 for subjecting
a work 15 to an induction heating, and a current transformer 13
provided between the matching capacitor 12 and the heating coil 14.
Thus, the induction hardening apparatus 10 has an equivalent
circuit configuration that includes the matching capacitor 12 and
the heating coil 14 including a parallel resonance circuit.
[0111] The high-frequency inverter 11 is a current-fed inverter and
is controlled so that the output voltage remains constant. The
current transformer 13 has a primary coil 13a parallely connected
to the matching capacitor 12 with regard to the high-frequency
inverter 11 and a secondary coil 13b parallely connected to the
heating coil 14.
[0112] According to the induction hardening apparatus 10, by
supplying high-frequency current from the high-frequency inverter
11 to the heating coil 14 while the work 15 is being placed in a
receiving unit (not shown) including the heating coil 14, eddy
current is caused in the work 15 to thereby heat the work 15 to
perform a hardening processing.
[0113] The induction hardening apparatus 10 is attached with
various sensors. Various sensors include: a sensor 11a as shown in
FIG. 1 for monitoring the output time and the output intensity from
the high-frequency inverter 11; a sensor (not shown) for detecting
the position, the transportation speed, or the rotation speed of
the work 15 for example; a flow sensor 115 as shown in FIG. 2 for
detecting the flow of the hardening liquid; a temperature sensor
116 as shown in FIG. 2 for detecting the temperature of the
hardening liquid; and a measuring unit 117 as shown in FIG. 2 for
measuring the cooling power or concentration of the hardening
liquid for example. The following section will describe these
sensors.
[0114] The sensor 11a is included in the high-frequency inverter 11
and detects the output time and the output intensity from the
high-frequency inverter 11.
[0115] The induction hardening apparatus 10 is attached with a
moving means or a rotary means (not shown). The moving means moves
the work from a predetermined position relative to the heating coil
14. The rotary means rotates the work relative to the heating coil
14. Thus, the induction hardening apparatus 10 is attached with
sensors for sensing whether the work 15 is accurately moved or
rotated by the moving means or the rotary means (specifically, a
position sensor, a rotation sensor, or a speed sensor for
example).
[0116] The induction hardening apparatus 10 shown in FIG. 1
includes, as shown in FIG. 2, a first cooling system 100 for
causing coolant to flow in the heating coil 14 and the second
cooling system 110 for jetting hardening liquid to the work 15 to
collect the liquid.
[0117] The first cooling system 100 has a configuration as
described below for example. The first cooling system 100 is
configured, as shown in FIG. 2, so that a coolant tank 101, a pump
103, and the heating coil 14 are connected by a piping. When the
work 15 shown by the dotted line is subjected to an induction
heating, coolant is caused to flow over the heating coil 14 in the
direction shown by the arrow. A flow sensor 102 is attached in the
middle of the piping. This flow sensor 102 detects the flow of the
coolant.
[0118] The second cooling system 110 has a configuration as
described below for example. The second cooling system 110 is
configured, as shown in FIG. 2, so that a jacket 111 surrounds the
work 15 shown by the solid line, a tank 113 stores therein
hardening liquid, and a pump 114 pumps up the hardening liquid from
the tank 113. The hardening liquid is sent, as shown by the arrow,
via the piping to the jacket 111 and is jetted from the jacket 111
toward the work 15 and is returned by a retrieving unit 112 to the
tank 113. The tank 113 has a heating unit 113a for controlling the
temperature of the hardening liquid. The tank 113 is attached with
a temperature sensor 116 for detecting the temperature of the
coolant in the tank 113. The piping between the pump 114 and the
jacket 111 is attached with the flow sensor 115. The measuring unit
117 is provided to measure the cooling power of the hardening
liquid. The measuring unit 117 measures the cooling power of the
hardening liquid in the tank 113 at an arbitrary timing or on a
real-time basis.
[0119] As shown in FIG. 3, the hardening monitoring unit 20
includes: a current sensor 21 for detecting the output current from
the high-frequency inverter 11; a voltage sensor 22 for detecting
the voltage in the heating coil 14; a controller 23 for monitoring
a hardening processing based on the detection signal from the
current sensor 21 and the detection signal from the voltage sensor
22; and the warning unit 24 for inputting various pieces of control
information to the controller 23 and for receiving a warning signal
from the controller 23.
[0120] The current sensor 21 is electrically connected to a wiring
of the high-frequency inverter 11 and the matching capacitor 12 and
detects the output current I.sub.o of the high-frequency inverter
11. The voltage sensor 22 has both ends including the terminals 22a
and 22b that are parallely connected to the heating coil 14 to
detect the voltage V.sub.coil of the heating coil 14.
[0121] The controller 23 includes: the current detection unit 23a
for receiving an input of a detection signal from the current
sensor 21; the voltage detection unit 23b for receiving an input of
a detection signal from the voltage sensor 22; the signal
processing unit 23c for receiving an input from the current
detection unit 23a and the voltage detection unit 23b to subject
the inputs to a signal processing, respectively; and the
determination unit 23d for receiving the input of the signal
processing by the signal processing unit 23c to determine whether
the result is within a predetermined range or not. The
determination unit 23d includes the display unit 23e for outputting
the result of the signal processing by the signal processing unit
23c.
[0122] The current sensor 21 and the current detection unit 23a may
be configured by a current transfer (current transformer) for
converting the detected current to a voltage. A Rogowski coil can
be used for the current sensor 21. The current detection unit 23a
converts the voltage generated in the Rogowski coil to a voltage
within a predetermined range. The current transfer converts the
output current of 500 A.sub.rms to 0.5V.sub.rms for example.
[0123] The voltage sensor 22 and the voltage detection unit 23b may
be configured by a potential transfer (transformer) for converting
the detected voltage to a voltage within a predetermined range. In
this case, the voltage sensor 22 can use a probe that can be
connected between the terminals of the heating coil 14. The voltage
detection unit 23b converts the voltage extracted by the probe to a
voltage within a predetermined range. The potential transfer
converts the coil voltage of 200V.sub.rms to 10V.sub.rms for
example.
[0124] The signal processing unit 23c rectifies the signals from
the current detection unit 23a and the voltage detection unit 23b
respectively to calculate effective values and removes noise by
filters to thereby output the current signal S.sub.i and the
voltage signal S.sub.v to the determination unit 23d. Thus, the
signal from the current transfer e.g., a signal of 0.5V.sub.rms is
converted to a voltage signal of 5V, while the signal from the
potential transfer e.g., a signal of 10V.sub.rms is converted to a
voltage signal of 5V.
[0125] Further, in response to a request from the data collecting
unit 80 as mentioned below, the signal processing unit 23c
transmits the calculated effective values, namely current signal
S.sub.i and voltage signal S.sub.v, to the data collecting unit
80.
[0126] The determination unit 23d determines whether the current
signal S.sub.i and the voltage signal S.sub.v inputted from the
signal processing unit 23c are appropriate or not. That is, by
receiving the heating synchronization signal S.sub.s from a
controller (not shown) for controlling the high-frequency inverter
11, the determination unit 23d extracts the waveforms of the
current signal S.sub.i and the voltage signal S.sub.v. Then, the
determination unit 23d displays the waveforms on the display unit
23e together. In this case, the determination unit 23d displays
upper-limit and lower-limit threshold values that are set in
advance. This allows the determination unit 23d to determine, when
the current signal S.sub.i and the voltage signal S.sub.v are
higher than the upper-limit threshold value or lower than the
lower-limit threshold value during the operation of the induction
hardening apparatus 10, that the determination is not fine to
thereby record the waveform as an abnormal waveform. The
determination unit 23d outputs a warning signal to the warning unit
24. The output of a warning signal may be performed by performing a
warning display of "Not Fine" on the display unit 23e.
[0127] The warning unit 24 performs a warning display based on the
warning signal from the determination unit 23d, generates warning
sound to the outside, or instructs a controller (not shown) of the
high-frequency inverter 11 to stop the output of high-frequency
power.
[0128] The following section will describe a circuit configuration
in the signal processing unit 23c of FIG. 3. The signal processing
unit 23c includes a current measurement circuit for processing a
signal from the current detection unit 23a and a voltage
measurement circuit for processing a signal from the voltage
detection unit 23b. The current measurement circuit and the voltage
measurement circuit have a similar circuit configuration.
Therefore, the voltage measurement circuit will be described
below.
[0129] FIG. 4 shows a voltage measurement circuit 30 in a signal
processing unit 23c in FIG. 3. The voltage measurement circuit 30
is structured so that the first operational amplifier 31 and the
second operational amplifier 32 are cascade-connected and the
output-side is connected to a filter circuit 33. The first
operational amplifier 31 is connected to input resistance 34, a
first diode 35 connected to an input terminal and an output
terminal, a second diode 36 having one end connected to an output
terminal, and resistance 37 having one end connected to an input
terminal and the other end connected to the other end of the second
diode 36. This first operational amplifier 31 is a so-called ideal
diode and performs a half-wave rectification of an input signal
voltage. The first operational amplifier 31 and the second
operational amplifier 32 are connected by resistance 38. The second
operational amplifier 32 is an inverting amplifier in which
resistance 39 is connected between an input terminal and an output
terminal. The second operational amplifier 32 has an input terminal
connected to the input signal-side of the input resistance 34 via
resistance 40. The output from the second operational amplifier 32
is a waveform obtained by subjecting the input voltage signal to a
full wave rectification. This full wave rectification waveform is
inputted to the low pass-type filter circuit 33 composed of the
resistance 41 and a capacitor 42. Then, the ripple of the full wave
rectification waveform is removed and the full wave rectification
waveform is converted to a DC voltage. By setting the value of the
resistance 41 and the capacitor 42 of the filter circuit 33, the
effective value of the wave by the full wave rectification
outputted from the second operational amplifier 32 is obtained.
[0130] The following section will describe in detail the relation
among the hardening control unit 70, the data collecting unit 80
and the hardening monitoring unit 20 shown in FIG. 1. The hardening
control unit 70, the hardening monitoring unit 20, and the data
collecting unit 80 are mutually connected by a communication means
(not shown). The communication means includes, for example, wired
communication by a LAN cable or an RS232C cable and wireless
communication such as wireless LAN. Data communication by wired
communication or wireless communication may be provided by parallel
transmission or serial transmission. The hardening control unit 70
and the high-frequency inverter 11 also may be connected by these
communication means.
[0131] As shown in FIG. 1, the hardening control unit 70 includes:
an input unit 71 for inputting input information such as setup
conditions data; a memory unit 72 for storing setup conditions data
inputted from the input unit 71; an output unit 73 for outputting
setup conditions data; and an input and output control unit 74 for
subjecting the setup conditions data to an input/output control.
The setup conditions data is data for setting the output intensity
and the output time from the high-frequency inverter 11 in the
induction hardening apparatus 10 and includes, for example, output
current, an output voltage, an output power, and an output time.
This setup conditions data also may include control data for
controlling the positional relation between the work 15 and the
heating coil 14 (e.g., control data of the moving means or the
rotary means of the work 15, control data of the pump 103 in the
first cooling system 100 or the pump 114 in the second cooling
system 110).
[0132] When measurement data is sent from the hardening monitoring
unit 20 to the hardening control unit 70 or when the hardening
control unit 70 causes the output unit 73 to output setup
conditions data to the high-frequency inverter 11 and measurement
data is sent to the hardening control unit 70 upon a transmission
request of then measurement data to the hardening monitoring unit
20, the measurement data generated by the hardening monitoring unit
20 is stored in the memory unit 72 of the hardening control unit 70
while being combined with the setup conditions data.
[0133] When the induction hardening apparatus 10 subjects a work to
an induction hardening based on the setup conditions data outputted
from the hardening control unit 70, the data collecting unit 80
receives data detected by various sensors in the induction
hardening apparatus (e.g., the sensor 11a, a detection sensor (not
shown) for detecting the position of the work 15, the carry-in
speed, or the rotation speed for example, the flow sensor 102 in
the first cooling system 100, the flow sensor 115 in the second
cooling system 110, the temperature sensor 116, the measuring unit
117) and stores the data. The data collecting unit 80 collects
these pieces of detection data from the induction hardening
apparatus 10, setup conditions data for each work from the
hardening control unit 70, and measurement data generated by the
hardening monitoring unit 20 for each induction hardening
processing and stores the data in an internal memory unit (not
shown).
[0134] The data editing unit 90 is configured by a general-purpose
computer for example. The data editing unit 90 reads setup
conditions data and measurement data for each work from the data
collecting unit 80 via a wired or wireless LAN to store the data.
The data editing unit 90 stores therein spreadsheet software for
example as a tool. The data editing unit 90 reads the detection
data from the induction hardening apparatus 10 and the setup
conditions data and the measurement data for each work to determine
the induction hardening quality for each work to allow a user to
input the determination result. The data communication between the
data collecting unit 80 and the data editing unit 90 may be
realized by the data transmission, for example by the RS232C, or by
storing the data in the data collecting unit 80 to a
separately-prepared recording medium (e.g., USB memory) to insert
the recording medium to the data editing unit 90 to copy the data
for example.
[0135] If the hardening control unit 70 is configured in a
different manner from the above-described one so that the detection
data from the induction hardening apparatus 10 and the setup
conditions data and measurement data are stored while having no
association among them at all, setup conditions data and
measurement data are acquired from the hardening control unit 70
based on a processing number attached to each work or an induction
hardening processing date for example. Then, the setup conditions
data and measurement data are associated with the detection data
outputted from the induction hardening apparatus 10 based on
association data such as an induction hardening processing time so
that the detection data as well as the setup conditions data and
measurement data can be stored as a combination.
[0136] The following section will describe a hardening monitoring
by the induction hardening control system 1 shown in FIG. 1.
[0137] The hardening control unit 70 outputs setup conditions to
the induction hardening system 10. Accordingly, in the induction
hardening apparatus 10, the high-frequency inverter 11 inputs
high-frequency power to the heating coil 14 via the matching
capacitor 12 and the current transformer 13 based on the input
setup conditions. Moving means in the induction hardening apparatus
10 moves the work 15 and rotary means in the induction hardening
apparatus 10 rotates the work 15. As a result, the work 15 placed
in the heating coil 14 is heated and is subjected to an induction
hardening. Then, in the induction hardening monitoring apparatus
20, the current sensor 21 detects the output current I.sub.o from
the high-frequency inverter 11 and the voltage sensor 22 detects
the voltage V.sub.coil of the heating coil 14. The sensor detects a
location, import speed, and rotation speed of the work 15. The flow
sensor 102 in the first cooling system 100 detects flow of coolant.
The temperature sensor 116 and the flow sensor 115 in the second
cooling system 110 detect temperature and flow of hardening liquid.
These detected data are output to the hardening control unit 70 or
data collecting unit 80 as the detected data from the induction
hardening system 10.
[0138] The current detection unit 23a and the voltage detection
unit 23b of the controller 23 adjusts the levels of the respective
detection signals from the current sensor 21 and the voltage sensor
22 respectively and outputs the current signal S.sub.i and the
voltage signal S.sub.v to the signal processing unit 23c. Then, the
signal processing unit 23c rectifies the current signal and the
voltage signal inputted from the current detection unit 23a and the
voltage detection unit 23b respectively to calculate effective
values and outputs the effective values as the current signal
S.sub.i and the voltage signal S.sub.v to the determination unit
23d.
[0139] The determination unit 23d synchronizes the current signal
S.sub.i and the voltage signal S.sub.v from the signal processing
unit 23c based on the heating synchronization signal S.sub.s to
determine the waveforms. Then, the determination unit 23d compares
the current signal S.sub.i and the voltage signal S.sub.v with the
upper-limit and lower-limit threshold values to determine whether
the current signal S.sub.i and the voltage signal S.sub.v are
higher than the upper-limit threshold value or not and/or whether
the current signal S.sub.i and the voltage signal S.sub.v are lower
than the lower-limit threshold value or not. When the current
signal S.sub.i and the voltage signal S.sub.v deviate from the
threshold value, the determination unit 23d records the waveform
and outputs a warning signal to the warning unit 24.
[0140] Upon receiving the warning signal, the warning unit 24
displays a warning and/or generates warning sound. Thus, upon
recognizing the warning display or the warning sound, a worker
performing a hardening can notice that abnormality is caused in the
induction hardening. The warning unit 24 may stop the output
operation of the high-frequency inverter 11 of the induction
hardening apparatus 10.
[0141] As described above, the current sensor 21 is used to detect
the output current from the high-frequency inverter 11. The voltage
sensor 22 is used to detect the voltage generated in the heating
coil 14. Based on the detection signal from the current sensor 21
and the detection signal from the voltage sensor 22, a hardening
processing is monitored. As a result, when high-frequency power is
inputted to the heating coil 14 via the capacitor 12 from the
high-frequency inverter 11 for which the output is controlled so
that the output power is constant, the fluctuation of the output
power from the high-frequency inverter 11 has a direct influence on
the output current. Thus, by monitoring this output current by the
current sensor 21, the output power from the high-frequency
inverter 11 can be monitored during the induction hardening
processing. On the other hand, by using the voltage sensor 22 to
monitor the voltage generated in the heating coil 14, an increased
detection sensitivity is obtained by the transmission loss from the
high-frequency inverter 11 to the heating coil 14 and/or the
matching loss by the parallel resonance circuit of the capacitor 12
and the heating coil 14. Thus, the fluctuation of the voltage of
the heating coil 14 can be detected accurately.
[0142] That is, when the power transmission loss is small, the
fluctuation rate of the output current due to a load fluctuation is
higher than the fluctuation rate of the coil voltage. Thus, it is
effective to monitor the output current from the high-frequency
inverter 11 by the current sensor 21. When the power transmission
loss is large on the other hand, the fluctuation rate of the coil
voltage due to the load fluctuation is higher than the fluctuation
of the output current from the high-frequency inverter 11. Thus, it
is effective to monitor the coil voltage by the voltage sensor 22.
On the contrary, when the output power is controlled so that the
high-frequency inverter has a constant output voltage in the method
described in the background art of monitoring the output current
and the output voltage of the high-frequency inverter, the load
fluctuation cannot be detected
[0143] FIG. 5(A) shows a load resonance circuit. FIG. 5(B) is a
diagram showing an equivalent circuit when the frequency of the
high-frequency is synchronized with the resonance frequency of the
load resonance circuit with regard to the load resonance circuit
shown in FIG. 5(A). The induction heating electric circuit shown in
FIG. 3 is represented, as shown in FIG. 5(A), by a circuit in which
the parallel connection of the matching capacitor C.sub.p, the load
resistance R.sub.p, and the load inductance L.sub.p is serially
connected to the resistance R.sub.x including the transmission loss
between the high-frequency inverter and the heating coil and the
matching loss. When the frequency of the high-frequency inverter is
synchronized with the frequency of the load resonance circuit in
the load resonance circuit shown in FIG. 5(A), the circuit shown in
FIG. 5(A) can be rewritten to the equivalent circuit shown in FIG.
5(B), i.e., a non-inductive resistance circuit. It is assumed that
the resistance including the matching loss and the transmission
loss between the high-frequency inverter and the heating coil is
R.sub.x, the load resistance is R.sub.p, the output voltage from
the high-frequency inverter is V.sub.o=300V, and the output
I.sub.o=300 A. It is assumed that Rx and R.sub.p are both
0.5.OMEGA. and the description will not be further provided. When
the load fluctuation causes a change of the resistance R.sub.p from
0.5.OMEGA. to 0.55.OMEGA. by +10%, the output voltage controlled to
be constant causes the output voltage V.sub.o to be unchanged at
300V and causes the output current I.sub.o to be changed from 300 A
to 285.7 A. Thus, the change rate of the output current is also
-4.8% and the output power changes by -4.8%. Then, the coil voltage
V.sub.coil changes from 150V (=300 A.times.0.5.OMEGA.) to 157.1V
(=285.7 A.times.0.55.OMEGA.), causing a change rate of the coil
voltage of +4.8%. That is, the decreasing rate of the output
current from the high-frequency inverter is substantially equal to
the increase rate of the coil voltage.
[0144] When the resistance R.sub.x including the transmission loss
and the matching loss is 0.4.OMEGA. and the load resistance R.sub.p
is 0.6.OMEGA. in the above circuit configuration, a case will be
considered where the change rate of the load resistance R.sub.p is
+10%, i.e., the load resistance R.sub.p changes from 0.6.OMEGA. to
0.66.OMEGA.. In this case, the output voltage V.sub.o of the
high-frequency inverter is unchanged at 300V and the output current
I.sub.o changes from 300 A to 283.0 A. Thus, the change rate of the
output current is also -5.7% and the output power changes by -5.7%.
Then, the coil voltage V.sub.coil changes from 180V (=300
A.times.0.6.OMEGA.) to 186.8V (=283.0 A.times.0.66.OMEGA.) and the
change rate of the coil voltage is about +3.8%. That is, the
decrease rate of the output current from the high-frequency
inverter has an absolute value that is higher than the absolute
value of the increase rate of the coil voltage.
[0145] When a case is considered where the resistance R.sub.x
including the transmission loss and the matching loss is 0.6.OMEGA.
and the load resistance R.sub.p is 0.4.OMEGA. in the circuit
configuration, the change rate of the load resistance R.sub.p is
+10%, i.e., the load resistance R.sub.p changes from 0.4.OMEGA. to
0.44.OMEGA.. In this case, the output voltage V.sub.o of the
high-frequency inverter is unchanged at 300V and the output current
I.sub.o changes from 300 A to 288.5 A. Thus, the change rate of the
output current is also -3.8% and the output power also changes by
-3.8%. Then, the coil voltage V.sub.coil changes from 120V (=300
A.times.0.4.OMEGA.) to 126.9V (=288.5 A.times.0.44.OMEGA.) and the
change rate of the coil voltage is about +5.7%. That is, the
decrease rate of the output current from the high-frequency
inverter has an absolute value that is lower than the absolute
value of the increase rate of the coil voltage.
[0146] From the above, it can be seen that, in the case of the
conventional method to monitor the output current and the output
voltage of a high-frequency inverter, with an increase of the
transmission loss and the matching loss, e.g., with an increase of
the ratio between the resistance R.sub.x including the transmission
loss and the matching loss and the load resistance R.sub.p from
0.4:0.6 through 0.5:0.5 to 0.6:0.4, the change rate of the output
current I.sub.o from the high-frequency inverter changes from -5.7%
through -4.8% to -3.8% and thus the output current from the
high-frequency inverter does not change in proportion with the
change rate of the load resistance R.sub.2, thus showing a poor
sensitivity to the fluctuation of the load resistance R.sub.p.
[0147] In contrast with this, by monitoring as in this embodiment
both of the coil voltage V.sub.coil and the output current I.sub.o
from the high-frequency inverter, the influence by the transmission
loss can be eliminated to monitor the load fluctuation. The reason
is that, in the case that the ratio of the transmission loss and
the matching loss is small, the fluctuation of the load resistance
has a bigger influence on the change rate of the output current
than on the fluctuation rate of the coil voltage and thus the
monitoring of the change of the output current from the
high-frequency inverter is preferred. In the case that the ratio of
the transmission loss and the matching loss is large on the
contrary, the fluctuation of the load resistance has a bigger
influence on the fluctuation rate of the coil voltage than on the
change rate of the output current and thus the monitoring of the
change of the coil voltage is preferred. That is, by monitoring
both of the coil voltage V.sub.coil and the output current I.sub.o
from the high-frequency inverter, a monitoring method is
established to eliminate an influence by the power loss in the
circuit.
[0148] After the induction hardening processing is performed in the
manner as described above, the data collecting unit 80 collects the
data regarding the induction hardening processing to a
predetermined work. Specifically, the data collecting unit 80
requests the hardening control unit 70 to send the search data
(e.g., the processing number, the induction hardening processing
date) as well as setup conditions data, measurement data, and
detection data. Then, the input and output control unit 74 of the
hardening control unit 70 identifies, based on the search data, the
setup conditions data, the measurement data, and the detection data
from the memory unit 72 to output the data to the data collecting
unit 80. In this manner, the data collecting unit 80 collects the
setup conditions data, the measurement data, and the detection
data.
[0149] In addition to this, another configuration also may be used
where the data collecting unit 80 requests the hardening control
unit 70 to simultaneously send the setup conditions data, the
measurement data, and the detection data and the data collecting
unit 80 collects the setup conditions data, the measurement data,
and the detection data to store, based on association data (e.g.,
an induction hardening processing date), the setup conditions data,
the measurement data, and the detection data in a database so that
the association thereamong can be established.
[0150] The data collection by the data collecting unit 80 also may
be performed, in addition to the communication means as described
above, by another configuration in which setup conditions data,
measurement data, and detection data stored in the memory unit 72
of the hardening control unit 70 are once stored in a recording
medium such as a card or a CD-ROM to subsequently insert the
recording medium to the data collecting unit 80.
[0151] Another configuration also may be used in which, if
detection data is directly inputted from the induction hardening
apparatus 10 to the data collecting unit 80, only setup conditions
data and measurement data are obtained from the data collecting
unit 80.
[0152] As described above, the data collecting unit 80 stores the
setup conditions data, the measurement data, and the detection data
in a database so that the association thereamong can be
established. The stored setup conditions data, measurement data,
and detection data can be searched and read by inputting
information identifying the induction hardening processing by the
data collecting unit 80. Thus, setup conditions data regarding a
desired induction hardening processing and associated measurement
data and detection data can be easily and quickly extracted to
thereby perform a control for the induction hardening processing in
a secure manner. Furthermore, the setup conditions data, the
measurement data, and the detection data stored in the data
collecting unit 80 can be stored, as required, in a medium (e.g., a
card, CD-ROM) and can be transferred to the data editing unit 90 as
shown in FIG. 1 so that a user can confirm the data by the data
editing unit 90 through spreadsheet software for example.
Second Embodiment
[0153] In the hardening unit 20 of the second embodiment, during an
induction hardening, the normality of the induction hardening
processing is monitored by monitoring load impedance i.e., a value
obtained by dividing a heating coil voltage by output current
outputted from a high-frequency inverter. An induction hardening
control system 1 including a hardening monitoring unit according to
the second embodiment has the same configuration as in the case of
FIG. 1 showing the first embodiment. Specifically, the induction
hardening monitoring apparatus according to the second embodiment,
specifically, an induction hardening control system 1 including an
impedance monitoring apparatus is composed, as shown in FIG. 1, of
an induction hardening apparatus 10, a hardening monitoring unit
20, hardening control unit 70 and a data collecting unit 80.
[0154] As shown in FIGS. 1 and 3, the induction hardening apparatus
10 is configured so that a matching capacitor 12 and a heating coil
14 form a parallel resonance circuit in an equivalent circuit-like
manner. In the second embodiment, the induction hardening apparatus
10 may be a series resonance circuit composed of a matching
capacitor and a heating coil. Although the high-frequency inverter
11 is a current-fed inverter as in the first embodiment, the second
embodiment is different from the first embodiment in that the
high-frequency inverter 11 is driven while being controlled based
on a constant power control method so that an outputted
high-frequency power is constant. The second embodiment is the same
as the first embodiment in that the current transformer 13 is
composed of the primary current-side coil 13a parallely connected
to the matching capacitor 12 with regard to the high-frequency
inverter 11 and the secondary current-side coil 13b parallely
connected to the heating coil 14.
[0155] According to the induction hardening apparatus 10, by
supplying high-frequency current from the high-frequency inverter
11 to the heating coil 14 while the work 15 is being placed in a
receiving unit (not shown) including the heating coil 14, eddy
current is caused in the work 15 to thereby heat the work 15 to
perform a hardening processing. Other configuration is same as
FIGS. 1 to 3.
[0156] The hardening monitoring unit 20 includes: a current sensor
21 for detecting the output current from the high-frequency
inverter 11; a voltage sensor 22 for detecting the voltage in the
heating coil 14; a controller 23 for calculating a load impedance
based on the detection signal from the current sensor 21 and the
detection signal from the voltage sensor 22 to monitor a hardening
processing based on this load impedance; and the warning unit 24
for inputting various pieces of control information to the
controller 23 and for receiving a warning signal from the
controller 23.
[0157] The current sensor 21 is electrically connected to a wiring
of the high-frequency inverter 11 and the matching capacitor 12 and
detects the output current I.sub.o of the high-frequency inverter
11. The voltage sensor 22 has both ends including the terminals 22a
and 22b that are parallely connected to the heating coil 14 to
detect the voltage V.sub.coil of the heating coil 14.
[0158] The controller 23 includes: the current detection unit 23a
for receiving an input of a detection signal from the current
sensor 21; the voltage detection unit 23b for receiving an input of
a detection signal from the voltage sensor 22; the signal
processing unit 23c for receiving an input from the current
detection unit 23a to calculate an effective value regarding the
output current and for receiving an input from the voltage
detection unit 23b to calculate an effective value regarding the
coil voltage; and the determination unit 23d for calculating a load
impedance based on the respective effective values regarding the
output current and the coil voltage calculated by the signal
processing unit 23c to thereby determine whether the load impedance
is within a reference interval or not. The determination unit 23d
includes the display unit 23e for outputting the result of the
signal processing by the signal processing unit 23c.
[0159] The current sensor 21 and the current detection unit 23a may
be configured by a current transfer (current transformer) for
converting the detected current to a voltage. The voltage sensor 22
and the voltage detection unit 23b may be configured by a potential
transfer (transformer) for converting the detected voltage to a
voltage within a predetermined range. These points are the same as
those of the first embodiment.
[0160] The signal processing unit 23c rectifies the signals from
the current detection unit 23a and the voltage detection unit 23b
respectively to calculate effective values and uses filters to
remove noise to thereby output the current signal S.sub.i and the
voltage signal S.sub.v to the determination unit 23d. This point is
the same as that of the first embodiment. The signal processing
unit 23c includes a current measurement circuit for processing the
signal from the current detection unit 23a and a voltage
measurement circuit for processing the signal from the voltage
detection unit 23b, respectively. The current measurement circuit
and the voltage measurement circuit have the same specific
configurations as those of the first embodiment. Thus, the signal
from the current transfer, e.g., a signal of 0.5V.sub.rms, is
converted to a voltage signal of 5V while the signal from the
potential transfer, e.g., a signal of 10V.sub.rms, is converted to
a voltage signal of 5V.
[0161] The determination unit 23d divides the coil voltage by the
output current based on the current signal S.sub.i and the voltage
signal S.sub.v inputted from the signal processing unit 23c to
thereby determine whether this calculated load impedance is within
a stipulated range or not. In particular, by receiving the heating
synchronization signal S.sub.s from a controller (not shown) for
controlling the high-frequency inverter 11, the determination unit
23d samples the values of the current signal S.sub.i and the
voltage signal S.sub.v inputted from the signal processing unit
23c. Next, the determination unit 23d divides the sampled voltage
value by the sampled current value and multiplies the result with a
predetermined proportional constant to thereby calculate the value
of the output current to the coil voltage, i.e., a load impedance.
Then, the calculation result is graphically displayed on the
display unit 23e during which whether the calculated load impedance
is within the reference interval or not is determined. When the
calculated load impedance is within the reference interval, the
determination unit 23d determines that the hardening processing is
fine. When the calculated load impedance is not within the
reference interval, the determination unit 23d determines that the
hardening processing is not fine to thereby display a warning
signal to the warning unit 24.
[0162] The determination unit 23d may be configured so as to be
able to output the waveform of any of the current signal S.sub.i
and the voltage signal S.sub.v to the display unit 23e upon
receiving the heating synchronization signal S.sub.s from a
controller (not shown) of the high-frequency inverter 11. In this
case, the determination unit 23d displays upper-limit and
lower-limit threshold values that are set in advance. This allows
the determination unit 23d to determine, when the current signal
S.sub.i and the voltage signal S.sub.v are higher than the
upper-limit threshold value or lower than the lower-limit threshold
value during the operation of the induction hardening apparatus 10,
that the determination is not fine to thereby record the waveform
as an abnormal waveform.
[0163] The determination unit 23d outputs a warning signal to the
warning unit 24. The output of a warning signal may be performed by
performing a warning display of "Not Fine" on the display unit
23e.
[0164] The warning unit 24 performs a warning display based on the
warning signal from the determination unit 23d, generates warning
sound to the outside, and instructs a controller (not shown) of the
high-frequency inverter 11 to stop the output of high-frequency
power.
[0165] The following section will describe a hardening monitoring
when the induction hardening system 1 is used to perform a
hardening processing. In the induction hardening apparatus 10, the
high-frequency inverter 11 inputs high-frequency power to the
heating coil 14 via the matching capacitor 12 and the current
transformer 13. As a result, the work 15 placed in the heating coil
14 is heated and is subjected to an induction hardening. Then, in
the induction hardening apparatus 10, the current sensor 21 detects
the output current I.sub.o from the high-frequency inverter 11 and
the voltage sensor 22 detects the voltage V.sub.coil of the heating
coil 14.
[0166] The current detection unit 23a and the voltage detection
unit 23b of the controller 23 adjust the levels of the respective
detection signals from the current sensor 21 and the voltage sensor
22 respectively and output the current signal S.sub.i and the
voltage signal S.sub.v to the signal processing unit 23c. Then, the
signal processing unit 23c rectifies the current signal and the
voltage signal inputted from the current detection unit 23a and the
voltage detection unit 23b respectively to calculate effective
values and outputs the respective effective current and voltage
values as the current signal S.sub.i and the voltage signal S.sub.v
to the determination unit 23d.
[0167] Upon receiving the current signal S.sub.i and the voltage
signal S.sub.v from the signal processing unit 23c, the
determination unit 23d synchronizes the current signal S.sub.i and
the voltage signal S.sub.v with the heating synchronization signal
S.sub.s to thereby acquire waveforms. Then, based on the respective
waveforms, the determination unit 23d acquires a data sequence of
the effective current value and the effective voltage value.
Thereafter, the determination unit 23d divides the effective
current value by the effective voltage value to thereby calculate a
load impedance and determines whether the calculated load impedance
is within a stipulated range or not. When the load impedance is not
within the threshold value, the determination unit 23d acquires and
records the data sequence and outputs a warning signal to the
warning unit 24.
[0168] During this, the determination unit 23d may compare the
effective current value with an upper-limit threshold value and a
lower-limit threshold value to determine whether the current signal
S.sub.i is higher than the upper-limit threshold value or is lower
than the lower-limit threshold value. When the current signal
S.sub.i deviates from the threshold value, the waveform is recorded
and a warning signal is outputted to the warning unit 24. This can
provide the monitoring as described later of a fluctuation in the
output from the high-frequency inverter 11. The fluctuation cannot
be determined by the monitoring of a load impedance.
[0169] Upon receiving the warning signal, the warning unit 24
displays a warning or generates warning sound. Thus, upon
recognizing the warning display or the warning sound, a worker
performing a hardening can notice that abnormality is caused in the
induction hardening. The warning unit 24 may stop the output
operation of the high-frequency inverter 11 of the induction
hardening apparatus 10.
[0170] As described above, the current sensor 21 is used to detect
the output current from the high-frequency inverter 11. The voltage
sensor 22 is used to detect a voltage generated in the heating coil
14. Based on the detection signal from the current sensor 21 and
the detection signal from the voltage sensor 22, the load impedance
is calculated and a hardening processing is monitored based on the
calculated load impedance. As a result, when high-frequency power
is inputted to the heating coil 14 via the capacitor 12 from the
high-frequency inverter 11 for which the output is controlled so
that the output power is constant, even when the output current
from the high-frequency inverter 11 has a low fluctuation rate and
the coil voltage generated in the heating coil 14 has a low
fluctuation rate, a deviation from a reference interval of a
positional relation between a work as a hardening target and a
heating coil, i.e., an increase of a gap d between the work 50 and
the heating coil (hereinafter referred to as a coil gap d) as shown
in FIG. 13, mentioned later, can be detected as a fluctuation of
the load impedance. Thus, the quality control of the induction
hardening processing can be performed easily and accurately.
[0171] The following section will describe the reason why the coil
gap d appears as the fluctuation of the load impedance even when
the output current from the high-frequency inverter 11 has a low
fluctuation rate and even when the coil voltage generated in the
heating coil 14 has a low fluctuation rate during an induction
hardening processing.
[0172] FIGS. 6(A), 6(B), and 6(C) are a schematic circuit diagram
for explaining the reason why the fluctuation of the coil gap d can
be observed as a load impedance fluctuation. FIG. 6(A) is an
equivalent circuit diagram illustrating a model of an induction
heating. FIG. 6(B) is an equivalent circuit diagram when no work
exists. FIG. 6(C) is a diagram showing the equivalent circuit shown
in FIG. 6(B) as a parallel circuit.
[0173] Among the induction heating electric circuits, the electric
circuit from the high-frequency inverter 11 to the heating coil 14
is shown in the point that, when a transmission loss R.sub.x is
omitted as shown in FIG. 6(A), the serial connection of a
resistance R1 and a self-inductance L1 is parallely connected to
the matching capacitor Cp. The work 15 is shown as a parallel
connection between a self-inductance L2 and a resistance R2. A
situation in which the work 15 is placed in the heating coil 14 can
be modeled as mutual-inductance. Here, R1 denotes a resistance
component of the coil conducting wire, R2 denotes a resistance
component of the heating target, L1 denotes an inductance component
of the heating coil 14, L2 denotes an inductance component of the
heating target, and M denotes a mutual-inductance that changes
depending on the gap between the heating coil 14 and the work 15.
When assuming that the coupling factor of the self-inductance L1
and the self-inductance L2 is k, the mutual-inductance M satisfies
the relation of k=M/(L1.times.L2).sup.1/2. The load impedance seen
from both ends of the matching capacitor Cp is represented by the
sum of a reactance component .omega.Le and a resistance component
Re. It is established that Le=L1(1-k.sup.2) and Re=R1+AR2. In the
formula, A is a factor determined depending on the above-described
coupling factor k, the load shape, and the heating frequency.
[0174] When the gap d between the work 15 and the heating coil 14
increases, the load coupling is reduced. An ultimate situation may
be that the load coupling is reduced until k=0 and Re=R1 are
reached and finally Le=L1 is reached. Specifically, the equivalent
circuit of FIG. 6(A) can be rewritten as shown in FIG. 6(B).
[0175] Furthermore, the serial equivalent circuit of FIG. 6(B) can
be converted to the parallel equivalent circuit of FIG. 6(C). Since
Ze=Re+jwLe is established, an admittance Ye is Ye=1/Ze and thus can
be represented by the following formula.
Ye=Gp+jBp
Gp and Bp are represented by the following formulae.
Gp=Re/(Re.sup.2+(.omega.Le).sup.2)
BP=.omega.Le/(Re.sup.2+(.omega.Le).sup.2)
In the formulae, Rp=1/Gp and |Xp|=1/|Bp|. Rp and |Xp| are
represented by the following formulae.
Rp=(Re.sup.2+(.omega.Le).sup.2)/Re
|Xp|=(Re.sup.2+(.omega.Le).sup.2)/(.omega.Le)
Since .omega.Le.sup.2>>Re.sup.2 is established in a hardening
application, the following formula is established.
Rp=(.omega.Le).sup.2/Re
|Xp|.apprxeq..omega.Le
[0176] In the formulae, .omega. denotes an angular frequency of a
high frequency outputted from the high-frequency inverter 11.
[0177] When the high-frequency inverter has a frequency that
corresponds to and that is synchronized with a frequency of the
load resonance circuit, the load impedance Z.sub.o can be
represented as:
Z.sub.o=R.sub.p=(.omega.Le).sup.2/Re
[0178] In other words, as is clear from the above approximation
formula, an increase in the gap d between the work 15 and the
heating coil 14 causes a decrease in the load coupling, an increase
in Le, a decrease in Re, and an increase in the load impedance
Z.sub.o. Furthermore, the load impedance Z.sub.o has a change rate
that is higher than those of Le and Re, respectively.
[0179] Therefore, when the output power from the high-frequency
inverter 11 is constant and the coil gap d increases, the output
current from the high-frequency inverter 11 decreases and the coil
voltage increases. Thus, even when the output current has a small
decrease rate and even when the coil voltage has a small increase
rate, the coil voltage ratio to the output current (i.e., load
impedance) increases. Thus, an increase in the coil gap d directly
appears as a fluctuation of the load impedance.
[0180] As can be seen from the above, when the output power of the
high-frequency inverter 11 is controlled to be constant in the
induction hardening processing, the fluctuation of the load
impedance is monitored by the determination unit 23d to confirm
that the fluctuation of the load impedance is within the range of
the upper-limit and lower-limit threshold values. By doing this,
the induction hardening monitoring can be performed efficiently.
Furthermore, the controller 23 preferably calculates the output
current from the high-frequency inverter 11 based on the detection
signal from the current sensor 21 to confirm that the fluctuation
of this output current is within the range of the upper-limit and
lower-limit threshold values. By doing this, whether the gap is
within an allowable range or not can be confirmed by monitoring the
load impedance. At the same time, the fluctuation of the output
current from the high-frequency inverter 11 can be monitored to
thereby confirm that energy required for the hardening is inputted,
thus providing a high-quality hardening control.
[0181] The measurement data generated by the hardening monitoring
unit 20 as described above is stored, as in the first embodiment,
in the memory unit 72 of the hardening control unit 70. Thus, as in
the first embodiment, the data collecting unit 80 requests, via a
communication means, the hardening control unit 70 for setup
conditions data, measurement data, and detection data also in the
second embodiment. Upon the request, the hardening control unit 70
sends the setup conditions data, measurement data, and detection
data for the induction hardening processing to the data collecting
unit 80 via the communication means. Then, upon receiving the setup
conditions data, measurement data, and detection data, the data
collecting unit 80 stores the received setup conditions data,
measurement data, and detection data in a database while being
associated to one another.
[0182] The setup conditions data, measurement data, and detection
data stored in the database as described above can be searched and
read by inputting information identifying the induction hardening
processing by the data collecting unit 80. Based on an instruction
from a user, the data editing unit 90 obtains the setup conditions
data, measurement data, and detection data from the data collecting
unit 80 and displays these pieces of data by spreadsheet software.
Therefore, the operator can confirm these pieces of data through
the spreadsheet displayed on a screen. In other words, the user can
always easily and quickly extract the setup conditions data
regarding the desired induction hardening processing as well as
associated measurement data and detection data also in the second
embodiment. Therefore, the second embodiment also can provide a
secure control for the induction hardening processing.
[0183] A modification example of the second embodiment will be
described.
[0184] FIG. 6 is a schematic diagram for explaining a modification
example of the present invention. The same components as those of
FIG. 29 are denoted with the same reference numerals. As shown by
the dotted line in FIG. 7, the ends 22c and 22d of voltage sensor
22 are arranged so that the voltages at both ends of the
semicircular portion 61a of the coil are detected as a coil
voltage. As a result, the fluctuation of the coil gap d can be
efficiently reflected on the load impedance.
[0185] A configuration as in this modification example is preferred
where the semicircular portion 61a is provided in which the heating
coil 61 is provided to have the predetermined gap d to the
hardening target region of the work 50 and, as shown by the dotted
line in FIG. 7, both end portions 22c and 22d of the voltage sensor
22 are connected to both ends of the semicircular portion 61a so as
to detect the voltage between the both ends of the semicircular
portion 61a. When this configuration where the end portions 22c and
22d of the voltage sensor 22 are connected to both ends of the
semicircular portion 61a as shown by the dotted line is compared
with a case where both ends 22a and 22b of the voltage sensor 22
are connected via the straight portions 61b, 61b as shown by the
solid line, the fluctuation rate of the coil gap can be detected
with a higher sensitivity, thus providing a more accurate hardening
monitoring.
[0186] From the above, when the high-frequency power is controlled
to be constant, an increase of the coil gap d causes an increase of
the load impedance and, based on this fluctuation of the load
impedance, whether the hardening processing is performed correctly
or not can be determined.
[0187] The induction hardening control system 1 according to the
second embodiment is not limitedly applied to the induction
hardening apparatus 10 shown in FIGS. 1 and 3. The induction
hardening monitoring apparatus according to the second embodiment
can be applied to an induction hardening apparatus having an
equivalent circuit configuration including a resonance circuit
having a matching capacitor and a heating coil and a high-frequency
inverter. For example, the current transformer 13 may be
omitted.
[0188] The following section will describe Examples 1 to 3 and
Comparison Examples 1 and 2 corresponding to the first embodiment
and Example 4 and Comparison Example 3 corresponding to the second
embodiment.
Example 1
[0189] The induction hardening control system 1 shown in FIG. 1 was
used to perform a load evaluation test.
[0190] As the high-frequency inverter 11, an inverter was used for
which a DC voltage was controlled to be constant to thereby output
a high frequency of 25 kHz. As a parallel resonance-type load
circuit, the matching capacitor 12 of 10 .mu.F and the current
transformer 13 having a turn ratio of 6:1 were used. Such a
saddle-type receiving unit including therein the heating coil 14
and receiving the work 15 was used that had an inner diameter of 40
mm and a width of 4 mm. The work 15 used was a circular pipe having
an outer shape of 33 mm and a thickness of 5.5 mm. In Example 1,
the work 15 was placed so that the gap between an end face of the
saddle-type receiving unit and the outer shape of the work has a
standard value of 4 mm. The output power from the high-frequency
inverter 11 was set to 50% of the set volume and the output power
from the high-frequency inverter 11 was set to be outputted for 1
second. For the determination unit 23d, the reference ranges for
the coil voltage V.sub.coil and the current I.sub.o were set in
advance. In detail, the work 15 was placed in a standard status to
the saddle-type receiving unit and then the work 15 was hardened.
Then, the current sensor 21 and the voltage sensor 22 were used to
sample the respective waveforms of the current signal S.sub.i and
the voltage signal S.sub.v. Then, it was confirmed that the quality
is within the predetermined range. Then, the sampled waveforms were
respectively assumed as reference waveforms and, along the
respective reference waveforms, an upper limit and a lower limit
were set for the voltage value on the vertical axis and the time on
the horizontal axis. In this Example, the upper and lower limit set
values for the voltage V.sub.coil was .+-.4.3% (.+-.50 mV), the
value set for the time axis was .+-.4.8 (.+-.48 ms), the upper and
lower limit set values for the current I.sub.o was .+-.3.8% (.+-.20
mV), and the value set for the time axis was .+-.4.8% (.+-.48
ms).
[0191] FIG. 8 shows the result of Example 1 in the first
embodiment. FIG. 8(A) shows a signal waveform corresponding to the
voltage in the heating coil 14. FIG. 8(B) shows a signal waveform
corresponding to the output current from the high-frequency
inverter 11. In the drawings, the solid lines represent the
respective waveforms and the dotted lines represent the range of
the upper-limit and lower-limit threshold values. In Example 1, the
gap is 4 mm of the reference value. Thus, as can be seen from FIGS.
8(A) and 8(B), the waveform is at substantially the center of the
upper-limit and lower-limit threshold values and the determination
by the determination unit 23d was "fine". The output power and the
output voltage from the high-frequency inverter 11 were 18 kW and
290V, respectively. The signal of the voltage V.sub.coil of the
heating coil 14 was 1.157V (which corresponds to V.sub.coil of
1.157.times.200/5V) and the signal of the output current I.sub.o of
the high-frequency inverter 11 was 0.529V (which corresponds to
I.sub.o of 0.529.times.500/5 A).
Example 2
[0192] Example 2 had the same configuration as that of Example 1
except for that the work 15 was placed so that the gap between the
end face of the saddle-type receiving unit and the outer shape of
the work 15 was 6 mm.
[0193] FIG. 9 shows the result of Example 2 in the first
embodiment. FIG. 9(A) shows a signal waveform corresponding to the
voltage in the heating coil 14. FIG. 9(B) shows a signal waveform
corresponding to the output current from the high-frequency
inverter 11. In the drawings, the solid lines represent the
respective waveforms and the dotted lines represent the range of
the upper-limit and lower-limit threshold values. In Example 2, the
gap is wider than the reference value of 4 mm. Thus, as can be seen
from FIGS. 9(A) and 9(B), although the waveform of the current was
at the lower limit-side than the substantially the center of the
upper-limit and lower-limit threshold values, the waveform of the
current was within the range of threshold values. Thus, the
determination by the determination unit 23d was "fine". The output
power and the output voltage from the high-frequency inverter 11
were 18 kW and 290V, respectively. The signal of the voltage
V.sub.coil of the heating coil 14 was 1.172V (which corresponds to
V.sub.coil of 1.172.times.200/5V) and the signal of the output
current I.sub.o of the high-frequency inverter 11 was 0.520V (which
corresponds to I.sub.o of 0.520.times.500/5 A).
Example 3
[0194] Example 3 had the same configuration as that of Example 1
except for that the work 15 was placed so that the gap between the
end face of the saddle-type receiving unit and the outer shape of
the work 15 was 7 mm.
[0195] FIG. 10 shows the result of Example 3 in the first
embodiment. FIG. 10(A) shows a signal waveform corresponding to the
voltage in the heating coil 14. FIG. 10(B) shows a signal waveform
corresponding to the output current from the high-frequency
inverter 11. In the drawings, the solid lines represent the
respective waveforms and the dotted lines represent the range of
the upper-limit and lower-limit threshold values. In Example 3, the
gap of 7 mm is further wider than the reference value of 4 mm.
Thus, as can be seen from FIGS. 10(A) and 10(B), the signal
waveform of the current was partially extruded from the lower limit
of the threshold value. Thus, the hardening processing is
determined as "not fine". The output power and the output voltage
from the high-frequency inverter 11 were 17 kW and 290V,
respectively. The signal of the voltage V.sub.coil of the heating
coil 14 was 1.162V (which corresponds to V.sub.coil of
1.162.times.200/5V) and the signal of the output current I.sub.o of
the high-frequency inverter 11 was 0.500V (which corresponds to
I.sub.o of 0.520.times.500/5 A).
Comparison Example 1
[0196] The following section will describe comparison examples.
[0197] In comparison examples, the induction hardening system 1 was
configured so that the current sensor 21 connected to the wiring
between the high-frequency inverter 11 and the matching capacitor
12 was connected, as shown by the broken line in FIG. 3, to the
primary-side of the current transformer 13 so that the current
sensor 21 detects the primary current I.sub.ctrl-1 of the
transformer.
[0198] As in examples 1 to 3, the output power from the
high-frequency inverter 11 was set to 50% of the set volume and the
output power from the high-frequency inverter 11 was set to be
outputted for 1 second. For the determination unit 23d, the upper
and lower limit set values for the voltage V.sub.coil were .+-.4.3%
(.+-.50 mV), the value set for the time axis was .+-.4.8 (.+-.48
ms), the upper and lower limit set values for the current I.sub.o
were .+-.3.8% (.+-.125 mV), and the value set for the time axis was
.+-.4.8% (.+-.48 ms). The reason is that, regarding the setting of
the upper and lower limit values for the current I.sub.o, since the
current to be measured as a target was changed from the output
current I.sub.o of the high-frequency inverter 11 to the primary
current I.sub.ctrl-1 of the current transformer 13, the current
value increases even when the upper and lower set values are set
within the same range (%).
[0199] In Comparison Example 1, the gap between the saddle-type
receiving unit and the work was set to 4 mm as in Illustrative
Embodiment 1.
[0200] FIG. 11 shows the result of Comparison Example 1 in the
first embodiment. FIG. 11(A) shows a signal waveform corresponding
to the voltage in the heating coil 14. FIG. 11(B) shows a signal
waveform corresponding to the primary-side current of the current
transformer 13. In the drawings, the solid lines represent
waveforms and the dotted lines represent the range of the
upper-limit and lower-limit threshold values.
[0201] In Comparison Example 1, since the gap has the reference
value of 4 mm, as can be seen from FIG. 11, the respective current
and voltage signal waveforms are both at substantially the center
of the upper-limit and lower-limit threshold values and the
determination by the determination unit 23d was "fine". The output
power and the output voltage from the high-frequency inverter 11
were 18 kW and 290V, respectively. The signal of the voltage
V.sub.coil of the heating coil 14 was 1.170V (which corresponds to
of 1.170.times.200/5V) and the signal of the primary current
I.sub.ctrl-1 was 3.287V (which corresponds to I.sub.ctrl-1 of
3.287.times.500/5 A).
Comparison Example 2
[0202] In Comparison Example 2, the hardening was performed in the
same manner as in Comparison Example 2 except for that the gap
between the saddle-type receiving unit and the work was 7 mm.
[0203] FIG. 12 shows the result of Comparison Example 2 in the
first embodiment. FIG. 12(A) shows a signal waveform corresponding
to the voltage in the heating coil 14. FIG. 12(B) shows a signal
waveform corresponding to the primary-side current of the current
transformer 13. In the drawings, the solid lines represent
waveforms and the dotted lines represent the range of the
upper-limit and lower-limit threshold values.
[0204] In Comparison Example 2, in spite of the gap wider than the
reference gap of 4 mm, as can be seen from FIG. 12, the signal
waveform of the voltage and the signal waveform of the primary-side
current of the current transformer 13 were both at substantially
the center of the upper-limit and lower-limit threshold values and
thus the determination by the determination unit 23d was "fine".
The output power and the output voltage from the high-frequency
inverter 11 were 17 kW and 290V, respectively. The signal of the
voltage V.sub.coil of the heating coil 14 was 1.166V (which
corresponds to V.sub.coil of 1.166.times.200/5V) and the signal of
the primary current I.sub.ctrl-1 was 3.281V (which corresponds to
of 3.281.times.500/5 A).
TABLE-US-00001 TABLE 1 Gap between work and Output Determination
unit receiving unit power Sv Si Determination [mm] [kW] [V] [V]
result Example 1 4.00 18 1.157 0.529 Fine Example 2 6.00 18 1.172
0.520 Fine Example 3 7.00 17 1.162 0.500 Not Fine Comparison 4.00
18 1.170 3.287 Fine Example 1 Comparison 7.00 17 1.166 3.281 Fine
Example 2
[0205] Table 1 shows the results of Examples 1 to 3 and Comparison
Examples 1 and 2. The results as shown below are obtained, in the
induction hardening system 1, when a case as in Illustrative
Embodiments 1 to 3 where the wiring between the high-frequency
inverter 11 and the matching capacitor 12 is electrically connected
to the current sensor 21 is compared with a case as in Comparison
Examples 1 and 2 where the wiring between the high-frequency
inverter 11 and the matching capacitor 12 is electrically connected
to the primary-side of the current transformer 13.
[0206] When the output current I.sub.o from the high-frequency
inverter 11 is detected as in Examples 1 to 3, when the gap is
increased from the reference value of 4 mm through 6 mm to 7 mm in
this order, the signal S.sub.i of the output current I.sub.o
detected by the current sensor 21 changes, when being converted to
a voltage, from 0.529V through 0.520V to 0.500V. When the change
rate from a case where the reference value is 4 mm is calculated,
the change rate is about -1.7% when the gap is 6 mm and the change
rate is about -5.5% when the gap is 7 mm. Thus, the determination
unit 23d can determine a deviation from .+-.3.8% of the upper-limit
and lower-limit threshold values (which is .+-.20 mV when being
converted to a voltage).
[0207] On the other hand, when the gap is increased from the
reference value of 4 mm to 7 mm as in Comparison Examples 1 and 2,
the output power (the value shown by the meter) increases from 18
kW to 17 kw. Thus, in spite of the change of about -5.5% of the
signal S.sub.i of the detected current, the current I.sub.ctrl-1 in
the determination unit 23d is substantially the same that in the
case where the gap is 4 mm. This is within the range of threshold
values. Thus, the determination unit 23d determines "fine". Thus,
when the primary-side current of the current transformer 13 is
detected as in Comparison Examples 1 and 2, the induction hardening
cannot be monitored accurately.
[0208] The reason of this will be considered below. Since the
comparison examples monitor the primary current I.sub.ctrl-1 as a
target, this is given by an equivalent circuit configuration of the
vector synthesis of the effective current flowing in the parallel
resistance and the reactive current flowing in the parallel
inductance (=(I.sub.R.sup.2+I.sub.L.sup.2).sup.1/2). Thus, a small
change of the gap between the work 15 and the heating coil 14
causes a small change of inductance. Thus, in the case that the
resonance sharpness Q is equal to or higher than 4 to 5, the above
vector synthesis does not significantly change even when the
effective current changes.
[0209] On the other hand, since in the present invention the
effective current is detected, a change of a parallel resistance
due to a change of the gap is directly and proportionally reflected
on the detection current. Therefore, a change of the monitoring
current can be detected easily.
Example 4
[0210] The induction hardening control system 1 shown in FIG. 1 was
used to perform a load evaluation test. A saddle-type coil was used
as the heating coil and a work was used as a hardening processing
target. FIG. 13 is a diagram showing the positional relation
between the heating coil 61 and a bar-like member as the work 50
according to Example 4 in the second embodiment of the present
invention. In FIG. 11, the same or corresponding members as those
of FIG. 29 are denoted with the same reference numerals.
[0211] As shown, the work 50 as a heating target is configured so
that the bar-like base portion 51 includes the extension portion 52
in a coaxial manner. Thus, the bar-like base portion 51 and the
extension portion 52 form a substantially L-like cross section. It
was assumed that the portion of the heating coil 61 opposed to the
straight portion 61b had a size a and the portion of the heating
coil 61 opposed to the semicircular portion 61a had a size b. It
was also assumed that the distance between the semicircular portion
61a of the heating coil 61 and the upper face 53 of the work 50,
i.e., the coil gap, was d. Such a high-frequency inverter 11 was
used that outputs high frequency having a frequency of 10 kHz and
for which the output power can be controlled to be constant without
depending on the load. As a parallel resonance-type load circuit,
the matching capacitor 12 in which four pieces of 4.15 .mu.F were
parallely connected and the current transformer 13 having a turn
ratio of 8:1 were used.
[0212] The heating coil 61 was placed to the work so that the coil
gap d was 1.5, 1.7, 1.9, 2.1, 2.3, and 2.5 mm, respectively. Then,
at each coil gap d, while the work 50 is being rotated around the
axis at a speed of 500 rpm, high-frequency power of 150 kW was
inputted for 5.5 seconds to thereby perform a hardening
processing.
[0213] In Example 4, the numerical value of the reference range of
the load impedance was set in the determination unit 23d in
advance. The reference range of the load impedance was set so that
the upper limit was 1.78.OMEGA. and the lower limit was
1.712.OMEGA.. Furthermore, the output current from the
high-frequency inverter was measured. The reference range of the
output current I.sub.o was set so that the upper limit was 290 A
and the lower limit was 250 A.
[0214] The following section will describe the result of Example 4.
FIG. 14 is a diagram showing the coil gap dependency of the load
impedance in the result of Example 4 of the second embodiment. FIG.
15 is a diagram showing the coil gap dependency to the load
impedance change rate in the second embodiment. FIG. 16 is a
diagram showing the coil gap dependency of the output current from
the high-frequency inverter in the second embodiment. FIG. 17 is a
diagram showing the coil gap dependency of the change rate of the
output current from the high-frequency inverter in the second
embodiment. In the drawings, all of the horizontal axes represent a
coil gap. The vertical axis in FIG. 14 represents the load
impedance. The vertical axis in FIG. 15 represents the load
impedance change rate. The vertical axis in FIG. 16 represents the
output current from the high-frequency inverter. The vertical axis
in FIG. 17 represents the change rate of the output current from
the high-frequency inverter. The change rate of each value was
calculated, when assuming that the value at the coil gap d was
f(d), by centuplicating the formula (f(d)-f(1.5))/f(1.5).
[0215] As can be seen from FIG. 14, the load impedance is
1.752.OMEGA. when the coil gap d has the standard value of 1.5 mm.
However, with an increase of d, the load impedance linearly
increases. When d is 2.1 mm, the load impedance exceeds the upper
limit of the reference range. As can be seen from FIG. 15, the
change rate of the load impedance increases by about 1.8% when d is
2.1 and increases to 2.6% when d is 2.5 mm.
[0216] As can be seen from FIG. 16, the output current from the
high-frequency inverter is about 267 A when the coil gap d has the
standard value of 1.5 mm. However, with an increase of d, the
output current from the high-frequency inverter linearly decreases
and decreases to about 262 A when d is 2.5 mm. As can be seen from
FIG. 17, the change rate of the output current decreases by 1.9%
when d is 2.5 mm.
[0217] Among the results of the forth embodiment 4 in the second
embodiment, FIG. 18 shows the waveform when the coil gap d is 1.5
mm. Among the results of the forth embodiment 4 in the second
embodiment, FIG. 18(A) shows the waveform of the load impedance.
FIG. 18(B) shows the waveform of the output current. FIG. 19 shows
the waveform when the coil gap d is 2.1 mm. FIG. 19(A) shows the
waveform of the load impedance. FIG. 19(B) shows the waveform of
the output current. As can be seen, in both of the case where the
coil gap d is 1.5 mm and the case where the coil gap d is 2.1 mm,
the load impedance rapidly increases by the start of the induction
hardening and then slightly decreases to subsequently increase. In
accordance with this, it can be seen that the output current
rapidly increases by the start of the induction hardening and then
slightly increases to subsequently slightly decrease. A similar
tendency was found when the coil gap d was 1.7 mm, 1.9 mm, 2.3 mm,
and 2.5 mm.
[0218] The above result shows that the change rate of the load
impedance to the coil gap d has an absolute value higher than that
of the change rate of the output current to the coil gap d. This
shows that, when an induction hardening processing is performed,
the induction hardening processing is preferably monitored by
measuring the load impedance. By monitoring the output current
I.sub.o from the high-frequency inverter, the stability of the
high-frequency inverter 11 can be inferred.
Comparison Example 3
[0219] Next, Comparison Example 3 is shown.
[0220] Comparison Example 3 is different from Example 4 in that the
load impedance is not used for monitoring and the coil voltage and
the output current from the high-frequency inverter are measured
for monitoring. The other conditions are the same as those of
Illustrative Embodiment 4.
[0221] Regarding the hardening monitoring, the determination unit
23d was set with the reference range of the coil voltage V.sub.coil
and the current I.sub.o in advance. In detail, the work 50 was
placed in a predetermined standard status and then the work 50 was
subjected to hardening. Then, the current sensor 21 and the voltage
sensor 22 were used to sample the respective waveforms of the
current signal S.sub.i and the voltage signal S.sub.v. Then, it was
confirmed that the quality was within the predetermined range.
Then, the respective sampled waveforms were used as a reference
waveform to set an upper limit and a lower limit for the voltage
value along the vertical axis and the time along the horizontal
axis along the respective reference waveforms. Then, the upper
limit of the coil voltage V.sub.coil was set to 61V and the lower
limit was set to 55V. The upper limit of the output current I.sub.o
was set to 290 A and the lower limit was set to 250 A.
[0222] The following section will describe the result of Comparison
Example 3. Among the results of the Comparison Example 3 in the
second embodiment, FIG. 20 is a diagram showing the coil gap
dependency of the coil voltage. Among the results of the Comparison
Example 3 in the second embodiment, FIG. 21 is a diagram showing
the coil gap dependency to the change rate of the coil voltage.
Among the results of the Comparison Example 3 in the second
embodiment, FIG. 22 is a diagram showing the coil gap dependency of
the output current from the high-frequency inverter. Among the
results of the Comparison Example 3 in the second embodiment, FIG.
23 is a diagram showing the coil gap dependency of the change rate
of the output current from the high-frequency inverter. In the
drawings, all of the horizontal axes represent a coil gap. In FIG.
20, the vertical axis represents a coil voltage. In FIG. 21, the
vertical axis represents the change rate of the coil voltage. In
FIG. 22, the vertical axis represents the output current from the
high-frequency inverter. In FIG. 23, the vertical axis represents
the change rate of the output current from the high-frequency
inverter. The change rate was calculated as in the illustrative
embodiments.
[0223] As can be seen from FIG. 20, the coil voltage is 58.8V when
the coil gap d has the standard value of 1.5 mm. However, with an
increase of d, the coil voltage linearly increases and is about
59.2V when d is 2.5 mm. As can be seen from FIG. 21, the change
rate of the coil voltage increases to 0.68% when d is 2.5 mm.
[0224] As can be seen from FIG. 22, the output current from the
high-frequency inverter is about 268.4 A when the coil gap d has
the standard value of 1.5 mm. However, with an increase of d, the
coil voltage linearly decreases and decreases to about 263 A when d
is 2.5 mm. As can be seen from FIG. 23, the change rate of the
output current decreases by about 1.9% when d is 2.5 mm.
[0225] Among the results of the Comparison Example 3 in the second
embodiment, FIG. 24 shows the waveform when the coil gap d is 1.5
mm. FIG. 24(A) shows the waveform of the coil voltage. FIG. 24(B)
shows the waveform of the output current. Among the results of the
Comparison Example 3 in the second embodiment, FIG. 25 shows the
waveform when the coil gap d is 2.1 mm. FIG. 25(A) shows the
waveform of the coil voltage. FIG. 25(B) shows the waveform of the
output current. In the drawings, the solid lines show the
respective waveforms and the dotted lines show upper limits and
lower limits of the range of threshold values. As can be seen from
FIG. 24, when the coil gap d is 1.5 mm, the voltage waveform was
almost at the neighborhood of the center of the upper-limit and
lower-limit threshold values. However, when the coil gap d is 2.1,
as can be seen from FIG. 25, the voltage waveform was almost at the
neighborhood of the center of the upper-limit and lower-limit
threshold values but the current waveform was not within the range
of the threshold values. Thus, the determination by the
determination unit 23d was "fine" when the coil gap d was 1.5 mm
but was "not fine" when the coil gap d was 2.1 mm. It is considered
that the reason why the coil voltage V.sub.coil and the output
current I.sub.o change in the case that an induction heating is
started without changing the coil gap d is that the heating
suppresses the work from being induction-heated.
[0226] As can be seen from the result of Comparison Example 3, an
increase of the coil gap d of 1 mm causes a decrease of about 2% of
the output current I.sub.o and an increase of about 0.7% of the
coil voltage V.sub.coil. The change rates are smaller when compared
with the change rates of the load impedance of Example 4.
[0227] As described above, the comparison of Example 4 with
Comparison Example 3 showed that the monitoring of the load
impedance is more effective than the monitoring of the output
current I.sub.o and the coil voltage V.sub.coil. Although the above
section has described a bar-like member as a work, the invention is
effective as a monitoring means when a structure in which a work
has a connected portion in a direction crossing an axis portion,
e.g., a flange or the neighborhood of the flange, is subjected to a
hardening processing. The reason is that, with an increase of the
distance between a hardening target region in the work and a
heating coil, a straight portion shows no change in a hardening
processing but a semicircular portion shows a poor hardening
processing, as shown in FIG. 13.
[0228] The following section will describe a modification example
of the system shown in FIG. 1. The first modification example shows
a case where the system configuration shown in FIG. 1 is changed in
the relation among the hardening control unit 70, the hardening
monitoring unit 20, and the data collecting unit 80. The second
modification example shows a case where there are a plurality of
combinations of the induction hardening apparatuses 10, the
hardening monitoring units 20, and the hardening control units 70
shown in FIG. 1 and these combinations are connected to the data
collecting unit 80 via a communication means such as LAN. The third
modification example shows a case where the induction hardening
apparatus is configured so that one high-frequency inverter 11
subjects a plurality of works to an induction hardening. In any of
these modification examples, the hardening monitoring unit 20 may
monitor current from the high-frequency inverter 11 and a coil
voltage outputted or the hardening monitoring unit 20 also may
calculate a load impedance to monitor the load impedance as
described above. The following section will describe in detail the
first modification example to the third modification example.
First Modification Example
[0229] FIG. 26 is a configuration diagram illustrating an induction
hardening control system 2 of the first modification example
different from the system configuration shown in FIG. 1. The
induction hardening control system 2 is different from the system
shown in FIG. 1 in that the data collecting unit 80 is connected to
the hardening control unit 70 and the hardening monitoring unit 20
via communication means, respectively. In this case, the data
collecting unit 80 collects measurement data from the hardening
monitoring unit 20, collects setup conditions data from the
hardening control unit 70, and collects detection data from the
induction hardening apparatus 10 to store, in a database, the
measurement data, the setup conditions data, and the detection data
to be associated with association data such as a processing date.
During this, the data collecting unit 80 may send a transmission
request to the hardening monitoring unit 20, the hardening control
unit 70, and the induction hardening apparatus 10, respectively or
the data also may be automatically sent at a predetermined timing
from the hardening monitoring unit 20, the hardening control unit
70, and the induction hardening apparatus 10, respectively. When
detection data is outputted from the induction hardening apparatus
10 to the hardening control unit 70 as described above, the data
collecting unit 80 collects measurement data and detection data
from the hardening control unit 70.
Second Modification Example
[0230] FIG. 27 is a configuration diagram illustrating an induction
hardening control system 3 according to the second modification
example. The induction hardening control system 3 is configured so
that there are a plurality of combinations of the induction
hardening apparatus 10, the hardening monitoring unit 20, and the
hardening control unit 70 so that the hardening control unit 70 in
each combination and the data collecting unit 80 are connected via
a communication means such as LAN. Specifically, one combination of
induction hardening systems 3A, 3B, and 3C is controlled by one
data collecting unit 80. In this case, the LAN connects the
hardening control units 70 to one another to send the setup
conditions data, measurement data, and detection data to the data
collecting unit 80. In this second modification example, the data
collecting unit 80 uses a sequencer control for example to request
the respective hardening control units 70 to send the setup
conditions data, measurement data, and detection data regarding the
induction hardening processing. Upon receiving the request as
described above, the hardening control unit 70 receives the
measurement data via the communication means from the hardening
monitoring unit 20 and sends this measurement data together with
the setup conditions data and the detection data to the data
collecting unit 80 via the LAN. Then, the data collecting unit 80
receives the setup conditions data, the measurement data, and the
detection data from the respective hardening control units 70 and
stores these pieces of data in a database so that the association
thereamong can be established. Thus, these pieces of data can be
subjected to a uniform control.
[0231] As described in the first modification example, another
configuration also may be used in which the LAN connects the
respective combinations of the hardening monitoring units 20 and
the hardening control units 70, respectively, and the data
collecting unit 80 stores the setup conditions data, measurement
data, and detection data in a database while being associated with
one another.
Third Modification Example
[0232] FIG. 28 is a configuration diagram illustrating an induction
hardening control system 4 according to the third modification
example. The induction hardening control system 4 is different from
the above-described induction hardening control systems 1, 2, and 3
in the induction hardening apparatus 10A. The induction hardening
apparatus 10A has an electric circuit configuration as shown in
FIG. 28 that includes: one high-frequency inverter 11; one matching
capacitor 12 connected between output terminals of the
high-frequency inverter 11; a plurality of heating coils 14A and
14B for subjecting works 15A and 15B to an induction heating,
respectively; a plurality of current transformers 13A and 13B
provided between the matching capacitor 12 and the respective
heating coils 14A and 14B, respectively; and a plurality of
switchers 16a and 16b provided between the primary input-side of
the plurality of current transformers 13A and 13B and one matching
capacitor 12, respectively. Each of the current transformers 13A
and 13B is composed of the primary current-side coil 13a parallely
connected to the matching capacitor 12 with regard to the
high-frequency inverter 11 and the secondary current-side coil 13b
parallely connected to the heating coils 14A and 14B, respectively.
The following section will describe a case as shown in FIG. 28 in
which the two heating coils 14A and 14B, the two current
transformers 13A and 13B, and the two switchers 16a and 16b are
provided. However, another configuration also may be used where
three or more heating coils and current transformers are provided
that are connected to the corresponding switchers. One heating coil
14A is serially connected to the secondary current-side coil 13b of
one current transformer 13A. The primary current-side coil 13a of
one current transformer 13A is parallely connected via one switcher
16a to the matching capacitor 12. Similarly, the other heating coil
14B is serially connected to the secondary current-side coil 13b of
one current transformer 13B. The primary current-side coil 13a of
the other current transformer 13B is parallely connected via the
other switcher 16b to the matching capacitor 12. Thus, one work 15A
can be subjected to an induction hardening processing by turning ON
one switcher 16a and turning OFF the other switcher 16b. Similarly,
the other work 15B can be subjected to an induction hardening
processing by turning OFF one switcher 16a and turning ON the other
switcher 16b. The switchers 16a and 16b are controlled by a switch
control unit (not shown) for example based on setup conditions
data. The example shown as the third modification example is also
configured so that the induction hardening apparatus 10 has an
equivalent circuit configuration in which the matching capacitor 12
and the heating coils 14, 14 include a parallel resonance
circuit.
[0233] When the induction hardening apparatus 10A subjects, as
shown in FIG. 28, a plurality of works 15A and 15B to an induction
heating by one high-frequency inverter 11, the hardening monitoring
unit 20 includes: one current sensor 21 for detecting the output
current from the high-frequency inverter 11; a plurality of voltage
sensors 22A and 22B for detecting the voltages in the respective
heating coils 14A and 14B; a control unit 23 for monitoring the
induction hardening based on the detection signal from the current
sensor 21 and the detection signals from the voltage sensors 22A
and 22B; and a warning unit 24 that inputs various control
information to the control unit 23 and that receives a warning
signal from the control unit 23. Specifically, the hardening
monitoring unit 20 has one current sensor 21 and the voltage
sensors 22A and 22B provided in the same number as that of the
heating coils 14A and 14B.
[0234] When the induction hardening apparatus 10A receives, as
setup conditions data from the hardening control unit 70, an output
control signal from the high-frequency inverter 11 and a switching
control signal from the switcher 16, a high frequency wave is
outputted from the high-frequency inverter 11 based on this setup
conditions data and the switchers 16a and 16b are switched. One
current sensor 21 is connected to a closed circuit between the
high-frequency inverter 11 and the matching capacitor 12. The
respective voltage sensors 22A and 22B are connected to closed
circuits provided between the heating coils 14A and 14B and the
secondary current-side coils 13b and 13b, respectively. Thus, the
hardening monitoring unit 20 receives the detection signal from the
current sensor 21 and the detection signals from the respective
voltage sensors 22A and 22B. Thus, the measurement data regarding
each induction hardening processing is inputted.
[0235] Thus, the induction hardening control system 3 according to
the third modification example has a similar configuration in which
the data collecting unit 80 obtains setup conditions data from the
hardening control unit 70, obtains measurement data from the
hardening monitoring unit 20 via the hardening control unit 70, and
obtains detection data from the induction hardening apparatus 10A
directly or via the hardening control unit 70 to store, in a
database, the setup conditions data, measurement data, and
detection data for each induction hardening processing with regard
to the respective works 15A and 15B. Another configuration as in
the first modification example also may be used in which the data
collecting unit 80 directly obtains measurement data from the
hardening monitoring unit 20. The data exchange other than this is
the same as the above-described one and will not be described
further.
[0236] In any of the induction hardening control systems 1 to 4
shown in FIG. 1 and FIG. 26 to FIG. 28, the data collecting unit 80
stores, in a database and in an integrated fashion, the setup
conditions data obtained from the hardening control unit 70, the
measurement data directly or indirectly obtained from the hardening
monitoring unit 20, and the detection data directly or indirectly
obtained from the induction hardening apparatus 10A. The following
section will describe an example of a data item in the hardening
control unit 70, the data collecting unit 80, and the hardening
monitoring unit 20.
[0237] The hardening control unit 70 stores therein, as setup
conditions data, the induction hardening processing number, an
induction hardening date, an induction hardening time, the
information for the position of the work at the start of the
induction hardening, the work transfer speed to the heating coil,
the set output value of the high-frequency inverter 11, instruction
information regarding whether coolant is jetted to the work or not,
or the work rotation speed for example.
[0238] The data stored in the data collecting unit 80 (i.e.,
detection data) obtained as a result of the setup conditions data
outputted from the hardening control unit 70 to the induction
hardening apparatuses 10 and 10A includes, for example, data
outputted from various sensors of the induction hardening
apparatuses 10 and 10A (e.g., the sensor 11a, the flow sensors 102
and 115, the temperature sensor 116, and the measuring unit 117).
Various sensors also include various meters included in the
induction hardening apparatuses 10 and 10A. Detection data items
include, for example, the induction hardening processing number,
the induction hardening date, the induction hardening time, the
information regarding the position of the work at the start of the
induction hardening, the output power from the high-frequency
inverter 11, the hardening liquid flow, and the rotation number of
the work.
[0239] Data stored in the hardening monitoring unit 20 includes:
the date of the trigger for sampling the detection signal from the
current sensor 21 and the voltage sensor 22; the instantaneous
value and the time-series value of an effective value of the
current sensor 21 and the voltage sensor 22; and the determination
result by the determination unit 23d for example. If an impedance
is calculated by the signal processing unit 23c, data stored in the
hardening monitoring unit 20 also includes an impedance
instantaneous value, a time-series value, and the determination
result by the determination unit 23d based on the impedance for
example.
[0240] Thus, the data editing unit 90 collects the data stored in
the hardening control unit 70, the data collecting unit 80, and the
hardening monitoring unit 20 so that the data for example can be
confirmed by a user through spreadsheet software for example. This
data is edited by a user so that the user can organize and confirm,
with regard to each induction hardening processing, the induction
hardening time, the position of the work at the start of the
induction hardening, the high frequency wave power, the hardening
liquid flow, and the work rotation number. Alternatively, the
induction hardening quality for each induction hardening processing
also can be controlled by setting conditions for an allowable range
with regard to the respective data items except for the induction
hardening processing number.
[0241] As described above, the data collecting unit 80 stores, in a
database, the setup conditions data regarding an induction
hardening processing of a certain work, the measurement data of the
electric quantity in an electric circuit configured between the
high-frequency inverter 11 and the heating coil 14, and various
pieces of detection data (e.g., the flow data for the coolant for
the heating coil 14, the hardening liquid flow data, temperature
data, cooling power data) for example. Furthermore, the setup
conditions data, measurement data, and detection data are stored
while being associated with one another with regard to each
induction hardening processing. Thus, the data stored in the data
collecting unit 80 can be read so that the induction hardening
conditions and various statuses during an actual induction
hardening can be associated to each other with regard to each work,
thus providing a comprehensive control to the induction
hardening.
[0242] The present invention can be changed within a scope not
deviating from the scope of the invention. For example, the data
editing unit 90 also may store, in a database, the setup conditions
data stored in the hardening control unit 70 and the measurement
data measured by the hardening monitoring unit 20 so that these
pieces of data are associated to each other.
[0243] The configurations of the electric circuits in the induction
hardening apparatuses 10 and 10A shown in FIG. 1 and FIG. 28 may be
changed arbitrarily. Various sensors provided in the induction
hardening apparatuses 10 and 10A also may be the ones other than
the one shown in FIG. 2 for example.
* * * * *