JPH0410380A - Induction heating control device - Google Patents

Abstract

PURPOSE:To save product cost and construction cost by using both of DC and AC coils as an induction heating means, providing a selector device for selecting output from both of the aforesaid coils, and feeding back the operation mode of a roll rotational speed detector and the signal thereof to the selector device. CONSTITUTION:A rotational speed detector 21 always detects the speed of a rotary roll 1 and transmits a rotational speed signal 22 to a feedback device 23. This feedback device 23 compares the signal 22 with a rotational speed lower limit value 24 set with a heating control device 10. When the level of the rotational speed signal 22 from the rotational speed detector 21 drops to or below the aforesaid lower limit value 24, a rotational speed drop signal 18 is outputted from the feedback device 23 to selector devices 25a to 25n. Then, the selector devices 25a to 25n fix DC heating instruction signals 9a to 9n at maximum levels, and gradually increase the levels of AC heating instruction signals 20a to 20n. As a result, induction heating due to AC oils 11a to 11n in addition to DC coils 6a to 6n starts, and the heating deficiency of the DC coils 6a to 6n is thereby compensated. According to the aforesaid construction, product cost and construction cost can be saved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an induction heating control device applied to rotating rolls of a paper machine.

(Prior Art) In general, induction heating devices include those that use a DC coil as a magnetic flux generation source and those that use an AC coil as their magnetic flux generation source, each having different characteristics.

First, an induction heating device using a DC coil will be explained based on FIG. In the figure, 1 is a rotating roll, 5 is a roll drive device, and 68 to 6n are DC coils. The rotating roll 1 is rotatable by the roll drive device 5, and a plurality of DC coils 6a6b---6n are rotated. They are arranged close to each other in the axial direction of the roll 1. And multiple excitation bags W8
a, 8b8n, respectively corresponding DC coils 6a.

6b--6n are excited, and this causes DC magnetic flux 17a, 17b1 to be applied to the surface of the rotating roll 1.
Supply 7n. At this time, eddy current is generated on the surface of the rotating roll 1, and the rotating roll 1 is heated by the Joule heat. On the other hand, from the heating control device 10, the excitation device 8
Heating command signals 9a, 9b--9 for a, 8b-8n
n is output, thereby making it possible to control the heating distribution on the shaft of the rotating roll 1.

A major feature of the induction heating device using a DC coil is that the energy for heating the rotating roll is transferred to the roll drive device 5.
This means that it will be covered by Figure 4 shows this situation. DC magnetic flux 1 is generated by DC coils 6a to 6n.
7a, 17b-17n are supplied to the surface of the rotating roll 1, a brake torque 15 generated when crossing the magnetic flux acts on the rotating roll 1. Therefore, if the current state remains as it is, the rotational speed of the rolls will decrease, so if the output of the roll drive device 5 is increased to increase the rotational torque 16, the rotational speed of the rolls will not decrease and the heating of the rolls will be reduced. sustained.

FIG. 5 shows a characteristic diagram of the amount of heating. The amount of heating increases as the DC currents 7a, 7b ---7n increase. This is because the aforementioned eddy current causes the DC magnetic flux 17a, 17b...
This is because it is proportional to the size of 17n. Similarly, the amount of heating increases as the rotational speed of the roll increases. This is because the surface of the rotating roll 1 has direct current magnetic flux 17a, 17b-.
This is because an eddy current is generated in proportion to the speed of crossing -17n. Therefore, when the rotating roll 1 is stationary, heating is not performed even if the DC currents 7a, 7b7n are passed.

Next, an induction heating device using an AC coil will be explained based on FIG. This AC induction heating device replaces the DC coils 6a, 6b-6n in FIG. 3 with AC coils lla, 1lb-6n.
1In, and the excitation devices 8a, 8b8n are replaced with inverters 12a, 12b-12n, and an alternating current magnetic flux 19a is applied to the surface of the rotating roll l.

19b-19n are supplied. The direction of these AC magnetic fluxes 19a, 19b-19n changes at a certain frequency, as shown in FIGS. 7, 8, and 9.
At this time, eddy current is generated and the surface of the rotating roll 1 is heated. Therefore, the amount of heating in an induction heating device using an AC coil differs from that in the case of a DC coil in that it does not depend on the roll rotation speed. Furthermore, the energy for heating is supplied by the inverters 12a, 12b-12n of FIG. 6, and not by the roll drive 5 as in the case of a DC coil.

(Problems to be Solved by the Invention) As described above, in the case of an induction heating device using a DC coil, the roll rotation speed is varied from a low speed range to a high speed range for operational conditions and operational purposes. When driving with frequent changes between speeds, there is a problem that the amount of heating in the low speed range is insufficient.

This is due to the characteristics of the DC coil as explained in FIG. Therefore, in such cases, it is sufficient to apply an induction heating device using an AC coil whose heating amount does not depend on the roll rotation speed, but an induction heating device using an AC coil does not heat the rotating roll. All of the energy for
There is a problem in that it must be supplied from a DC coil, and larger power equipment must be provided than in the case of a DC coil.

In particular, when installing an induction heating device using an AC coil in an existing rotating roll device, it is necessary to newly install the power supply equipment, which poses the problem of increasing product cost, construction cost, and construction period. there were.

The present invention uses both a DC coil and an AC coil as induction heating means, is provided with a selection device for selecting the output of both, and is further provided with a roll rotation speed detector and a feedback device that feeds back its signal to the selection device. This is an attempt to solve the above-mentioned conventional problems.

(Means for Solving the Problems) For this reason, the present invention provides a DC coil and an AC coil that are disposed close to a rotating roll that can be rotated by a roll drive device, and selects the DC coil through an excitation device. The AC coil is connected to the device, and the AC coil is connected to a selection device via an inverter, and the selection device is controlled based on the rotation speed of the rotating roll and the signal from the heating control device, This is a means to solve problems.

(Function) The feedback device of the present invention compares the roll rotation speed signal with the lower limit value of the roll rotation speed that can be set arbitrarily,
When the former becomes smaller than the latter, a command is issued to the selection device to start heating by the AC coil in addition to or instead of heating by the DC coil, so that there is no shortage even in the low speed range. The amount of heating can be maintained. In addition, if the capacity of the roll drive device is sufficient, by using both a DC coil and an AC coil,
The power supply equipment for the AC coil can be made smaller than when only the AC coil is used.

(Example) Hereinafter, the present invention will be described based on an example of the drawings. FIG. 1 is a configuration diagram of an induction heating control device of the present invention.

In Figure 1, ■ is a rotating roll, and this rotating roll 1
are provided with shafts 2a and 2b, and these shafts 2a and 2b
are bearings 3a provided in support frames 4a and 4b,
3b. A roll drive device 5 for rotating the rotary roll 1 is attached to one end of the shaft 2a, and a rotation speed detector 21 for detecting the rotation speed of the roll is attached to the roll drive device 5. It is being Further, DC coils 6a to 6n and AC coils lla to lln are arranged close to the rotating roll 1, and the DC coils 68 to 6n are connected to an excitation device 88 to 8n, and the AC coils lla to lln are connected to an inverter. 12a
-12n to selection devices 25a-25n. The selection devices 25a to 25n are for selecting either heating of the roll by a DC coil or an AC coil, or heating of the roll by both at the same time.
It is operated based on a signal from the heating control device 10 and a signal from the feedback device 23, which issue a heating command signal to the heating control device 12n. In addition, the DC coil 6
Effect of heating the roll by 8 to 6n and AC coil ll
The roll heating effect by a to 11n is the same as that of the conventional example, so its explanation will be omitted here.

Here, it is assumed that the rotational speed of the rotary roll 1 decreases for some operational reason while induction heating is being performed only by the DC coils 6a, 6b ---6n. On the other hand, the rotational speed detector 21 constantly detects the rotational speed of the rotating roll 1 and transmits the rotational speed signal 22 to the feedback device 23. The feedback device 23 compares this signal with a rotational speed lower limit value 24 arbitrarily set by the heating control device 10. and rotation speed detector 2
When the magnitude of the rotational speed signal 22 from 1 becomes equal to or less than the rotational speed lower limit value, the rotational speed reduction signal 18 is selected by the selection device 25.
a, output to 25b-25n. Then the selection device 25a
, 25b-25n fix the DC heating command signals 9a and 9b9n to the maximum (100%), and furthermore, the AC heating command signal 2
Increase 0a, 20b-2On. As a result, in addition to the DC coils 6a, 6b...-6n, the AC coil 11a,
Induction heating by l1b--4In is started, and it becomes possible to compensate for the insufficient heating of the DC coils 6a, 6b-6n. In this case, AC coil lla, 1lb-4I
Viewed from the n side, part of the total heating amount is transferred to the roll drive device 5.
Inverters 12a, 12b -
--The size of the 12n power supply equipment is AC coil Ila,
It can be made smaller than when only llb-11n is used.

Next, the manner in which the AC heating command signal is increased will be explained.

FIG. 2 shows how the heating output of the DC coil decreases when the roll rotation speed decreases. Initially, it is assumed that the rotation speed of the roll is sufficiently high and the heating characteristics of the DC coil follow the dotted line. It is assumed that the DC current (DC heating command signal) at this time is 50% and the heating amount is P. Next, if the roll rotation speed decreases for some reason and the heating characteristics become like the solid line, even if the DC current (DC heating command signal) is increased to 100% of the maximum,
The amount of heating decreases to Q. Therefore, in such a case, by issuing an AC heating command signal corresponding to -Q and starting induction heating by the AC coil, the insufficient heating energy can be supplemented.

(Effects of the Invention) As described above, according to the present invention, even if the roll rotation speed decreases for some reason, the necessary amount of heating can be supplied via the AC coil, ensuring stable heating energy at all times. be able to. In addition, the size of the power supply equipment required for AC induction heating can be made smaller than when using only AC induction heating, which reduces the product cost and construction cost of induction heating equipment.
Alternatively, excellent effects such as being able to save the construction period can be achieved.

[Brief explanation of drawings]

Fig. 1 is a system diagram of an induction heating control device according to an embodiment of the present invention, Fig. 2 is an explanatory diagram showing changes in the output of the DC coil when the roll rotation speed decreases, and Fig. 3 is a conventional DC induction heating device. Fig. 4 is a principle diagram of DC induction heating, Fig. 5 is a heating characteristic diagram of a DC coil, Fig. 6 is a perspective view of a conventional AC induction heating device, and Figs. 7 and 8 are AC induction heating devices. FIG. 9 is an explanatory diagram showing changes in magnetic flux over time. FIG. 9 is a diagram showing changes in alternating current and alternating current magnetic flux density over time. Explanation of main parts of the figure 1-Rotating rolls 2a, 2b--Axes 3a, 3
b --Bearing 4a, 4b -Support frame 5・
- Roll drive device 68~6n-DC coil 78~7
n-DC current 88-8n-Exciting device 9a-9n-DC heating command signal 1〇-Heating control device 11a-11 DC coil 1
2a-12 rr-Inverter 14a=14n--AC current 17a-17n-DC magnetic flux 18-Rotational speed reduction signal 19a"-19rt-m-AC magnetic flux 20a-20rt-AC heating command signal 21-Rotational speed detector 22-・Rotation speed signal 23-
Feedback device 24 - Rotation speed lower limit value 25 - Selection device 26a to 26n
- Heating command signal Fig. 2 M direct electric A most missing Fig. 4 Fig. 5 Kabutsu Fig. 3! Figure 446

Claims (1)

[Claims] A DC coil and an AC coil are disposed close to a rotating roll that can be rotated by a roll drive device, the DC coil is connected to a selection device via an excitation device, and the AC coil is selected via an inverter. An induction heating control device connected to the device and capable of controlling the selection device based on the rotational speed of the rotating roll and a signal from the heating control device.