Note: Descriptions are shown in the official language in which they were submitted.
CA 02328010 2000-12-12
INDUCTIVE HEATING ROLLER APPARATUS
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an inductive heating
roller apparatus.
2. Description of the R la d Art
As commonly known, the inductive heating roller apparatus
is structured by arranging an inductive heat generation
mechanism provided with an inductive coil inside a rotating
roller. In such the structure, when the inductive coil is
excited by the AC power source, the magnetic flux is generated
along the shaft center direction of the roller, and the magnetic
flux passes through a closed magnetic path one portion of which
is formed of the peripheral wall of the roller, and by this
magnetic flux, the current is induced in the roller, and the
peripheral wall of the roller is heat-generated by the Joule
heat due to this current.
As being understood by this description, because the
closed magnetic path for the generated magnetic flux is a single
closed magnetic path including the peripheral wall of the
roller, the AC power source to excite the inductive coil is
limited to a single phase power source. On the one hand, in
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general factories, because three-phase power source is a main
power source, it is required that the inductive coil is excited
by the three-phase power source.
However, in order to obtain the single phase voltage from
the three-phase power source, when two lines of the three-
phase lines are used, and the single phase voltage is obtained
from between the two lines, and this voltage is applied onto
each inductive coil, the unbalance of the power source is
generated between the case of two lines between which the
inductive coil is connected, and the case of two lines between
which the inductive coil is not connected. Accordingly, the
utilization efficiency of the power source is lowered.
SLTNMARY OF THE INVENTION
The object of the present invention is to apply the single
phase voltage onto the roller without generating any unbalance
in the three-phase power source, when the three-phase power
source is used as the power source for the roller heat
generation.
In the structure of the present invention, an inductive
heat generation mechanism having an inductive coil is arranged
inside a rotating roller, an inverter having a three-phase
power source as an input power source, and outputting the single
phase voltage by the phase conversion is prepared, and the
single phase output voltage from the inverter is applied onto
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the inductive coil as the exciting voltage.
As an inverter, an inverter using, for example, a SCR,
or a transistor can be appropriately used. Also in any one
of inverters, in order to obtain the single phase voltage from
the three-phase voltage, the three-phase voltage is converted
once into the DC voltage, and the DC voltage is converted again
and the single phase voltage is obtained. In such the manner,
when the single phase voltage obtained from the three-phase
voltage is used for the excitation of the inductive coil, no
unbalance is generated in the three-phase power source which
is the input power source.
When a plurality of inductive coils constituting the
inductive heat generation mechanism are provided, the single
phase voltage obtained from the inverter may also be applied
on each of inductive coils as the exciting voltage. In this
case, when the single phase voltage applied onto each of
inductive coils is the same phase to each other, the closed
magnetic path for the magnetic flux induced by each of inductive
coils, is independent of each other, and the interference does
not occur with each other.
A value of the single phase output voltage of the inverter
can be adjusted by changing an arc angle of SCR constituting
the inverter. Accordingly, in the case where a plurality of
inverters are prepared, and respective single phase output
voltage are applied onto respective inductive coils, when each
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of inverters is independently adjusted, an amount of the
magnetic flux induced by each of inductive coils can be
adjusted, and accordingly, the peripheral wall temperature of
the roller can be freely changed along the length direction of
the roller.
Accordingly, in one aspect, the present invention resides
in an induction heating roller apparatus comprising: a
rotating roller; an inductive heat generation unit arranged in
said rotating roller; a plurality of inductive coils arranged
in the shaft center direction of said roller, being provided
in said inductive heat generation unit; an input power source
being a three phase power source; and an inverter outputting a
single phase voltage, wherein the single phase voltage
outputted from said inverter is applied to said inductive coil
as an exciting voltage; and wherein the rotating roller
includes: a plurality of temperature sensors provided on said
rotating roller and each outputting a first signal
corresponding to a portion of said roller corresponding to one
of said plurality of inductive coils; and a plurality of
temperature adjusters comparing the first signal from said
each temperature sensor with a set temperature value of each
said inductive coil and outputting a second signal
corresponding to a difference based on the comparison into
said inverter, wherein said inverter adjusts said single phase
voltage in accordance with the second signal.
In another aspect, the present invention resides in an
induction heating roller apparatus, comprising: a rotating
roller; an inductive heat generation unit arranged in said
rotating roller; a plurality of inductive coils arranged in
the shaft center direction of said roller, being provided in
said
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inductive heat generation unit; an input power source being a
three phase power source; and a plurality of inverters, each
inverter outputting a single and same phase voltage, wherein
the single and same phase voltage outputted from each of
inverters is respectively applied to each of inductive coils
as an exciting voltage; and wherein the rotating roller
includes: a plurality of temperature sensors provided on said
rotating roller and each outputting a first signal
corresponding to a portion of said roller corresponding to one
of said plurality of inductive coils; and a plurality of
temperature adjusters comparing the first signal from said
each temperature sensor with a set temperature value of each
said inductive coil and outputting a second signal
corresponding to a difference based on the comparison into
said inverter, wherein said inverter adjusts said single phase
voltage in accordance with the second signal.
In yet a further aspect, the present invention resides in
an induction heating roller apparatus comprising: a rotating
roller; an inductive heat generation unit arranged in said
rotating roller; a plurality of inductive coils arranged in
the shaft center direction of said roller, being provided in
said inductive heat generation unit; an input power source
being a three phase power source; and an inverter outputting a
single phase voltage, wherein the single phase voltage
outputted from said inverter in applied to said inductive coil
as an exciting voltage; and wherein the rotating roller
includes: temperature sensors provided on said rotating roller
and each outputting a first signal corresponding to a portion
of said roller corresponding to one of said plurality of
inductive coils; and
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temperature adjusters comparing the first signal from said
each temperature sensor with a set temperature value of each
said inductive coil and outputting a second signal
corresponding to a difference based on the comparison into
said inverter, wherein said inverter adjusts said single phase
voltage in accordance with the second signal.
BRIEF DESCRIPTION FO THE DRAWINGS
Fig. 1 is a sectional view showing a first embodiment of
the present invention;
Fig. 2 is a circuit diagram for an inductive heat
generation mechanism shown in Fig. 1;
Fig. 3 is a sectional view showing a second embodiment of
the present invention;
Fig. 4 is a circuit diagram for the inductive heat
generation mechanism shown in Fig. 3;
Fig. 5 is a sectional view showing still a third
embodiment of the present invention;
Fig. 6 is a circuit diagram for the inductive heat
generation mechanism shown in Fig. 5;
Fig. 7 is a sectional view showing yet a fourth
embodiment of the present invention; and
Fig. 8 is a sectional view showing still yet a fifth
embodiment of the present invention.
DETAILED DESCRIPTION FO THE PREFERRED EMBODIMENT
Referring to the drawings, an embodiment of the present
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invention will be described below. In Fig. 1, numeral 1 is
a roller main body, numeral 2 are journals integrally provided
on its both sides, andarerotatablysupportedthrough bearings,
not shown, on the base. Numeral 3 is jacket chambers provided
inside the peripheral wall of the roller 1, and a plurality
of the jacket chambers are formed by drilling by, for example,
a drill, and end portions of each of the jacket chambers 3 are
communicated to each other. Inside each of jacket chambers
3, a heating medium of two phase of gas-liquid is filled.
Numeral 4 is an inductive heat generation mechanism and
supported by a supporting rode 5. The supporting rod 5 is
inserted into the journal 2, and supported by the journal 2
through a bearing 6. The inductive heat generation mechanism
4 is structured by an iron core 7 and an inductive coil 8 wound
around the iron core 7. A power source lead wire 9 connected
to the inductive coil 8 passes through the inside of a
supporting rod 5, and is led out to the outside from its end
portion of the supporting rod 5.
Numeral 11 is a temperature sensor inserted into the
peripheral wall of the roller main body 1, and is used for
detecting the temperature of the peripheral wall of the roller
main body 1, and outputs a voltage signal corresponding to the
temperature. This voltage signal is sent to a temperature
signal transmission mechanism 13 through a signal lead wire
12. Specifically, the temperature signal transmission
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mechanism 13 structured by a rotation transformer composed of
a pair of coils which are magnetically connected, is used.
In the drawing, a stator 14 provided with a stator side
coil is supported by the supporting rod 5, and a rotor 15
provided with a rotator side coil is supported by the journal
2. A signal lead wire 12 is connected to the rotor side coil.
The voltage corresponding to the temperature of the peripheral
wall of the roller main body 1 is sent to the rotor side coil
through the signal lead wire 12. Then, the voltage is
transmitted to the stator side coil connected to this coil.
By measuring this voltage, the temperature of the peripheral
wall of the roller main body 1 is obtained. This measured value
is taken out from an output terminal 16 to the outside.
According to the present invention, three phase power
source is used as the power source. In Fig. 2, numeral 20 is
the three phase power source, and numeral 21 is an inverter
whose input power source is the three phase power source and
which outputs the single phase AC voltage. The inverter 21
is mainly structured by a rectifying apparatus to rectify the
three phase voltage, and an SCR circuit or a transistor circuit
to convert the DC voltage from the rectifying apparatus into
the single phase AC voltage. In the structure of the present
invention, an arbitrarily structured one of this kind of
inverters may be appropriately used.
Numeral 22 is an output circuit of the inverter 16, and
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the single phase voltage is outputted from this circuit. The
single phase voltage outputted from this output circuit 22 is
applied onto the inductive coil 8 through the power source lead
wire 9 and excites it. A voltage signal from the signal lead
wire 12, that is, the voltage signal obtained from the stator
side coil of the temperature signal transmission mechanism 13
is supplied from an output terminal 16 to a temperature adjuster
24. The voltage signal is compared here to a set temperature
value of the roller main body 1, and a signal corresponding
to the difference is sent to the inverter 20. In the inverter
20, according to the signal, the arc angle of the SCR is adjusted,
and the single phase output voltage value is adjusted. Thereby,
the surface temperature of the roller main body 1 is adjusted
to the setting value.
In the above structure, the voltage obtained from the three
phase power source 20 is inputted into the inverter 21, and
the single phase voltage obtained from it, is applied onto the
inductive coil 8 in the rotating roller main body 1 from the
output circuit 22. Thereby, the magnetic flux is generated
and the current is induced in the peripheral wall portion of
the roller main body 1, and by this current, the roller main
body 1 is heat-generated. In this case, because the inverter
21 rectifies the three-phase voltage and converts it into the
single phase voltage, even when the inverter 21 outputs the
single phase voltage, no unbalance is generated on the
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three-phase power source 20 side.
In second embodiment of the present invention shown in
Fig. 3, as the inductive heat generation mechanism 4, the
following one is shown, which is structured such that, around
a long-sized cylindrical iron core which is structured by
cylindrically laminating the long-sized steel plate bent so
as to be along the involution curve, (refer to Japanese Utility
Model Registration No. 2532986), a plurality of (6 in the
example in the drawing) inductive coils 8 which commonly uses
this iron core 7, are wound in parallel. The power source lead
wire 9 is respectively connected to each of inductive coils
8.
Further, the inverter 21 has a plurality of output circuits
22, and the single phase and same phase AC voltage is outputted
from each output circuit 22. This output voltage is applied
onto each inductive coil 8 through the power source lead wire
9, and excites the coil 8. The other structure is not
specifically different from that of Fig. 1.
In the case where generally the long-sized iron core is
commonly used and the inductive heat generation mechanism is
structured by winding 3 or its multiple inductive coils around
the iron core in parallel, when each of inductive coils is
excited by the three-phase power source, the magnetic flux
induced by it crosses also the other inductive coils through
the commonly used iron core. Thereby, the magnetic flux
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induced in each of inductive coils interferes with each other.
When in this manner, the magnetic flux induced by each
of inductive coils interferes with each other, even when V phase
in U. V, W phases of the three-phase circuit is made to opposite
phase, and the voltage whose phase is shifted by 60 each is
applied onto each of inductive coils, and the phase difference
of the voltage applied onto each of inductive coils is reduced,
the current induced in each of inductive coils is influenced
on each other. Specifically, there is a tendency that the phase
of the current induced in the inductive coil connected to the
U phase is more delayed compared to the current induced in the
other inductive coils connected to V phase and W phase, and
the power factor is lowered. Accordingly, the unbalance is
generated onto the load between phases. Of course, the power
source unbalance among three-phase lines is also generated,
and the utilization efficiency of the power source is also
lowered.
However, as shown in Fig. 3 and Fig. 4, when the same and
single phase voltage from the inverter 21 is applied onto each
of inductive coils 8 and excites that, even when the iron core
is commonly used, because there is no phase difference in the
power source to excite each of inductive coils, there is no
variation of the power factor by the relative interference with
each other. Thereby, there is no generation of the unbalance
on the three-phase power source side and the unbalance on the
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load side.
The structure shown in Fig. 3 shows a case in which one
temperature sensor 11 is arranged, and the exciting voltage
of each of inductive coils 8 is simultaneously controlled in
the same manner. According to this, there is an advantage that
the surface temperature of the roller main body 1 is uniformly
controlled over its whole surface. However, there is a case
where the surface temperature in each portion of the roller
main body 1 is required to be controlled quickly responding
to its change, or a case where the surface temperature in each
portion along the shaft center direction of the roller main
body 1 is required to be controlled to a partially different
value, depending on the purpose of use of the roller main body
1.
The structure corresponding to such the requirement, is
a third embodiment of the present invention as shown in Fig.
5. As easily be understood from Fig. 5, a plurality of
temperature sensors 11 are prepared. Then, these are arranged
at positions opposite to the arrangement positions of each of
inductive coils 8, in the peripheral wall of the roller main
body 1. Further, as shown in Fig. 6, the same number as the
inductive coils 8, of the inverters 21 and the temperature
adjusters 24 are prepared. Of course, the single phase voltage
outputted from each of inverters 21 is in the same phase as
each other.
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The output voltage of each of inverters 21 is applied onto
each of inductive coils 8 through the power source lead wire
9. Further, the temperature signal detected by each of
temperature sensors 11 is sent to each of temperature adjusters
24. The output voltage of the inverter 21 is controlled by
the output of each of temperature adjusters 24. The other
structure is not specifically different from that of Fig. 3
and Fig. 4. According to this structure, in the same manner
as in the structure shown in Fig. 3, the unbalance on the
three-phase power source side and the load side is not
generated.
Then, each temperature along the shaft center direction
on the surface of the roller main body 1 is detected by each
temperature sensor 11, and corresponding toits detection value,
the output voltage of each of inverters 21 is adjusted. In
this case, in the case where the temperature setting values
set in all of temperature adjusters 24 are the same, when the
temperature on the surface of the roller main body 1 is
partially changed, the changed portion is detected by the
temperature sensor 11, and the inverter 21 corresponding to
this is controlled through the temperature adjuster 24
corresponding to the temperature sensor 11.
According to this, the surface temperature of the roller
main body 1 can be restored quickly responding to its change.
Further, when the temperature setting value set to each of
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temperature adjusters 24 is an objective temperature value in
each portion of the roller main body 1, the temperature of each
portion can be controlled to the same temperature as the setting
value.
In Fig. 7, a fourth embodiment of the present invention
is shown. The structure shown in Fig. 7 is a structure in which
a plurality of inductive heat generation mechanisms 4 composed
of iron cores 7 and inductive coils 8 are arranged along the
shaft center direction of the roller main body 1. In this case,
the structure is as follows: when yokes 18 are provided on both
sides of each of inductive heat generation mechanisms 4, the
magnetic path in each of inductive heat generation mechanisms
4 is independent of each other, and the magnetic flux passing
through each of magnetic paths does not interfere with each
other.
When generally, the yoke 18 is provided in this manner,
even when each of inductive coils is directly excited by the
three-phase power source, each magnetic path can be
theoretically independent of each other, however, actually,
the leakage magnetic flux is generated although it is a slight
amount, and there is a case in which it passes through the other
magnetic paths. Accordingly, it is vary difficult to delete
the unbalance on the power source side and the load side.
Further, as shown in the drawing, in the case where 3 or
its multiple of inductive heat generation mechanisms are
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provided, when each of them is equally connected to the
three-phase lines, even though the unbalance on the power
source side can be reduced, when the other numbers of inductive
heat generation mechanisms are provided, these can not be
equally connected to the three-phase lines, and as the result,
the generation of the unbalance as described above can not be
avoided.
However, even in such the case, the inverter 21 whose input
is the three-phase voltage as shown in Fig. 4, is prepared,
and when the inductive coil 8 of each of inductive heat
generation mechanisms 4 is excited by the output voltage of
the inverter 21, in the same manner as in each embodiment, no
unbalance on the three-phase power source side and the load
side is generated.
A fifth embodiment shown in Fig. 8 corresponds to Fig.
5, and a plurality of temperature sensors 11 are arranged
corresponding to each of inductive heat generation mechanisms
4. In this case, in the same manner as in the case shown in
Fig. 6, a plurality of inverters 21 and temperature adjusters
24 may be prepared. According to this, the heat generation
temperature of the roller main body 1 portion corresponding
to each of inductive heat generation mechanisms 4 can be
controlled independently of each other, in the same manner as
in Fig. 5.
The inverter used for the phase conversion in the present
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invention, has an adjusting function which can arbitrarily set
and change the frequency of its output voltage. By utilizing
the function, an another advantage is obtained other than
advantage that the single phase power source is obtained. That
is, the principle of inductive heat generation in the inductive
heating roller apparatus is that: the alternating magnetic flux
crosses the roller main body, and thereby, the short circuit
current in which the roller main body is one turn, is induced
in the peripheral wall of the roller main body. Further, when
this magnetic flux passes through the wall thickness portion
of the peripheral wall of the roller main body, the eddy current
is generated. By the Joule heat due to this short circuit
current and the eddy current, the roller main body is heated.
Generally, in the case of the low frequency current, it
is well known that its depth of penetration becomes large.
Accordingly, when the frequency of the current generated in
the roller main body is low, the heat generation due to the
short circuit current is dominant. Reversely, in the case of
the high frequency current, its depth of penetration becomes
small. Accordingly, when the frequency of the current
generated in the roller main body is high, the heat generation
due to the eddy current is dominant over the others.
Accordingly, when the frequency of the single phase output
voltage of the inverter applied onto the inductive coil as the
exciting voltage is adjusted and the frequency of the
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alternating magnetic flux generated by the inductive coil is
selected, so that the impedance matching can be obtained
corresponding to the wall thickness, inner diameter, diameter
of the inductive coil, and length, then, the highly efficient
operation condition can be selected.
Further, when the roller main body is formed of the
magnetic material, the roller main body itself performs an
action as the magnetic path. Accordingly, the short circuit
current and the eddy current are generated here, and the roller
main body is heated. In contrast to this, when the roller main
body is formed of the non-magnetic material such as stainless
steel, aluminum, or copper, the roller main body itself does
not perform an action as the magnetic path, and the alternating
magnetic flux generated by the inductive coils pass through
the external space of the inductive coils, and a part of that
flux crosses the roller main body.
The short circuit current flows in the roller main body
corresponding to the crossed magnetic flux as described above,
and on the other hand, the magnetic flux does not pass in such
a manner that the magnetic flux penetrates the wall thickness
portion of the roller main body in the axial direction, but
passes in such a manner that it crosses the roller main body
toward the radial direction, and goes out of the external space
of the roller main body, and at this time, the eddy current
is generated only by the magnetic flux which crossed the roller
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main body.
Accordingly, in the case where the roller main body is
formed of the non-magnetic material, when, by appropriately
adjusting the output frequency of the inverter, the frequency
of the alternating magnetic flux generated by the inductive
coil is made high and the number of alternation of the magnetic
flux is increased, and the eddy current is increased, then,
even when the roller main body is formed of the non-magnetic
material in which it is conventionally difficult to be
inductively heat-generated, it can effectively be inductively
heat-generated.
Incidentally, because, when the output frequency of the
inverter is increased, the depth of penetration of the current
is decreased, and the heat generation due to the short circuit
current is decreased, when the frequency of the single phase
output voltage of the inverter which is applied onto the
inductive coil as the exciting voltage is adjusted, and the
frequency of the alternating magnetic flux generated by the
inductive coil is selected so that the increase of the eddy
current and the decrease of the short circuit current are
balanced and the impedance matching is obtained, then, the good
efficient operation condition can be selected. Accordingly,
the frequency range appropriate for its use is appropriately
10 Hz - 1 kHz.
According to the present invention as described above,
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even when the three-phase power source is utilized as the
exciting power source and it excites the inductive coil of the
inductive heat generation mechanism, by using the inverter and
converting the three-phase into the single phase, the unbalance
is not generated on the three-phase power source side nor load
side, and accordingly, the three-phase power source can be
effectively utilized. Further, the following effects can also
be attained: when the three-phase power source is used in this
manner, even when a plurality of inductive heat generation
mechanisms are provided, and the heat generation temperature
of the peripheral wall of the roller is partially and
arbitrarily controlled, the utilization efficiency of the
three-phase power source is not lowered, and further, when the
inverter whose output frequency can be freely adjusted and set,
is used, by selecting its output frequency, the good efficient
operation condition can be selected, and even the roller,
formed of non-magnetic material in which conventionally the
inductive heat generation is difficult, can be effectively
inductively heat-generated.
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