JPS61208773A - Induction heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to an induction heater comprising a frequency conversion circuit including a heating coil and a cooling fan motor for cooling components of the frequency conversion circuit. .

<Prior art> In conventional induction heaters, the voltage value applied to the 7-amp motor that cools the components of the inverter circuit as a frequency conversion circuit is constant, so there is a difficulty in cooling the components in the inverter circuit. Ta.

In other words, since a large amount of current flows through the inverter circuit,
There are many parts that self-heat due to this current (and it is no exaggeration to say that the inverter circuit parts should be considered for cooling each component of the induction heater. However, the current flowing through the inverter circuit is and thickness depending on the type of pot being heated (varies. The degree of change depending on the type of pot is a big factor, and in general, the cooling fan motor is designed to match the current that flows most through the inverter circuit. There is.

However, in the case of pots with good heating effects (generally iron pots), the current flowing through the inverter circuit is small, so less cooling capacity is required, while the voltage applied to the cooling fan motor is constant. There was a tendency that the noise caused by the fan was bothersome.

Purpose: In view of the above, the present invention makes it possible to control the voltage applied to the cooling fan motor to increase in the case of a pot with poor heating effect, that is, a pot where the current flowing through the frequency conversion circuit exceeds a specified value. The present invention relates to induction heaters.

<Example> Embodiments of the present invention will be described below based on the drawings.

First, a first embodiment of the present invention shown in FIGS. 1 to 3 will be described. In this embodiment, a frequency conversion circuit 2 including a heating coil 1 and a cooling device for cooling the component parts of the frequency conversion circuit 2 are explained. A detector 4 is provided to detect the current of the frequency conversion circuit 2, and the output value (voltage value) detected by the detector 4 is equal to the reference value V.
A control circuit 5 is provided for controlling the voltage value applied to the cooling fan motor 3 to increase when the voltage value exceeds d.

The frequency conversion circuit 2 is, for example, an inverter circuit, and converts a DC power source smoothed and rectified from an AC power source 6 through a rectifier circuit 7 (diode bridge), a choke coil 8, and a smoothing capacitor 9 to a switching element 10 (transistor).
By performing ON-OFF control, magnetic flux is generated from the heating coil 1 to heat the load pan 11 placed above the heating coil 1. The frequency conversion circuit 2 includes a resonant capacitor 12 and a damper diode 13 that absorbs the reversely applied voltage of the switching element 10.

Furthermore, an inverter control circuit 14 for generating high frequency pulses is connected to the base side of the switching element 10.

The cooling fan motor 3 is a DC motor that rectifies the secondary side voltage of a transformer 15 connected to an AC power source 6 using a rectifying circuit 16 (diode bridge), and then rectifying the secondary side voltage of a transformer 15 connected to an AC power source 6.
It is operated by a smoothed power supply. The control circuit 5 that controls the cooling fan motor 3 includes a resistor 18
It consists of a drive element 19 (transistor) connected in series, a resistor 20 connected in parallel with the series connection body, and a drive circuit 21 that controls the drive element 19 ON-OFF. The cooling fan motor 3 is connected in series to the parallel connection body of the resistor 18, drive element 19, and resistor 20.

Further, the detector 4 consists of a current transformer provided in the frequency conversion circuit 2, and the output signal of the detector 4 is input to the drive circuit 21.

The drive circuit 21 includes a resistor Rd for forming a waveform similar to the current of the heating coil 1 as shown in FIG. A capacitor Ca for detecting the peak value Vc of the input voltage, a discharge resistor Re for discharging the charge of the capacitor Ca, and the peak value Vc.
and a comparator 22 that compares the value obtained by dividing the DC voltage Vs to the drive circuit 21 by the resistors Ra and Rd.

In the above configuration, the principle of induction heating is that high frequency pulses generated from the control circuit 14 cause the switching element 10 to
is turned OFF to cause a high frequency current to flow through the frequency conversion circuit 2 (inverter circuit), and the load pan 11 is heated by the magnetic flux generated from the heating coil 1 in the frequency conversion circuit 2 (inverter circuit). Then, the current of the heating filter 1 is detected by the detector 4, and the magnitude thereof is determined by the drive circuit 21,
When the value is greater than or equal to the reference value Vd, the drive element 19 is turned on. When the drive element 19 is turned on, the resistors 18 and 20 are connected in parallel, so that the voltage applied to the cooling fan motor 3 increases.

FIG. 3 shows the input and output waveforms of the drive circuit 21, in which (a) shows when the heating fill current is small, and (b) shows when the heating coil current is large. In this drive circuit 21, the output Va of the detector 4 has a waveform similar to the current of the heating coil 1 by selecting an appropriate value for the load resistance Rd. Therefore, by half-wave rectifying the output Va with a diode Da and charging the capacitor Ca, the input V of the drive circuit 21 is
The peak value of a can be detected. This peak value is VC, and this peak value Ve and DC voltage Vs are connected to a resistor R
The comparator 22 compares a and the voltage divided by Rh, and if the peak value Vc is higher, the output vb of the comparator 22 becomes H. Then, when the output vb becomes H, the drive element 19 is turned on.

In this manner, when the heating fill current exceeds the reference value Vd, the voltage applied to the cooling fan motor 3 increases, the air volume increases, and heat generation in the inverter components is suppressed, making it possible to provide a safe induction heater.

FIG. 4 shows a second embodiment of the present invention, in which a high-frequency voltage obtained by an auxiliary coil 3o in which the power supply circuit of a cooling fan motor 3 is inductively coupled to a heating coil 1 is transferred to a rectifier circuit 3.
1 and smoothed by a capacitor 32. The other configurations are the same as those of the first embodiment.

In the above configuration, when the heating coil current is small, the voltage applied to the cooling fan motor 3 becomes small, and when the current of the heating filter 1 is larger than the specified value, the voltage applied to the cooling fan motor 3 can be further increased. can.

FIG. 5 shows a third embodiment of the present invention, and is a circuit diagram when the resistor in series with the driving bare hand 19 in the first embodiment is eliminated, that is, the resistor 18 is set to 0Ω, and the configuration of the pond is shown in FIG. is the same as in the first embodiment above.

The above configuration also provides the same functions and costs as the first embodiment.

FIG. 6 shows a fourth embodiment of the present invention, in which two power supply circuits for the cooling fan motor 3 are provided.
and a diode 37 are connected in series, and the second power supply circuit 38 is formed by connecting the drive element 19 and the second power supply 39 (first power supply and second power supply) in series to the first power supply 35 and the diode 37. It is connected in parallel to a series connection body.

In the above configuration, normally the first power source 35 drives the cooling fan motor 3, and when the current of the heating filter 1 exceeds a specified value, the drive element 19 is turned on and the second power source 39 drives the cooling fan motor 3.
The cooling fan motor 3 is driven, and the voltage applied to the cooling fan motor 3 is increased.

It should be noted that the present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention.

For example, the current flowing through the frequency conversion circuit 2 may be detected by the current 11 of the heating coil 1 as in the first embodiment;
Another current value i2 of the frequency conversion circuit 2 shown in the figure. i3. i
4. A similar effect can be obtained by detecting is.

Effect> As is clear from the above description, the present invention provides an induction heater equipped with a frequency conversion circuit including a heating filter and a cooling fan motor for cooling the components of the frequency conversion circuit. A detector is provided to detect the current of the conversion circuit, and a control circuit is provided to increase the voltage value applied to the cooling fan motor when the output value detected by the detector exceeds a reference value. The present invention relates to an induction heater characterized in that it is provided with an induction heater.

Therefore, according to the present invention, when the heating coil current exceeds the reference value, the voltage applied to the cooling fan motor increases;
The increased air volume suppresses heat generation in inverter components, providing a safe induction heater.

[Brief explanation of the drawing]

Fig. 1 is a control circuit diagram of an induction heater showing a first embodiment of the present invention, Fig. 2 is a circuit diagram of the same drive circuit, and Fig. 3 (a) = (
b) is an input/output waveform diagram of the drive circuit, FIG. 4 is a control circuit diagram of an induction heater showing a second embodiment of the present invention, and FIG. 5 is a power supply of a cooling fan motor showing a third embodiment of the present invention. Circuit diagram, FIG. 6 is a power supply circuit diagram of a cooling fan motor showing a fourth embodiment of the present invention. 1: heating filter, 2: frequency conversion circuit, 3: cooling fan motor, 4: detector, 5: control circuit.

Claims (1)

[Claims] In an induction heater comprising a frequency conversion circuit including a heating coil and a cooling fan motor for cooling components of the frequency conversion circuit, a detector for detecting a current in the frequency conversion circuit is provided, and the detection 1. An induction heater comprising: a control circuit configured to increase a voltage applied to the cooling fan motor when an output value detected by the cooling fan motor exceeds a reference value.