JPH0245313B2 - - Google Patents

Description

[Detailed description of the invention] Industrial applications The present invention relates to an induction heating cooker.

Structure of the conventional example and its problems In FIG. 1, a heating coil 1 is fixed on the upper side of a coil base 3, and a magnet 2 is provided in the center to constitute a heating coil section. Commercial power is then supplied from the power supply 7 to the high frequency power converter 9 via the switch 8 . The high frequency output converted to high frequency is connected to the heating coil 1. heating coil 1
is excited to generate lines of magnetic force and induction heat the pot 6, which is an object to be heated, placed on the top plate 5. When the pot 6 is removed, the magnet 2 naturally falls due to its own weight, so the micro switch 4 is turned off, the high frequency power converter 9 stops operating, and heating is stopped. In this way, when the pot is placed, the pot detection device 10 consisting of the magnet 2 and the micro switch 4 is turned on and heated, and when the pot is removed, the heating is automatically turned off.

As described above, the conventional pot detection device 10 is located almost in the center of the heating coil, and is designed to only determine whether or not a pot is present on the top plate 5, automatically control heating, and bring about a power saving effect. It was hot.
Therefore, even if a pot 6 smaller in diameter than the heating coil 1 is placed, the pot detection device 10 works to heat the pot.
Now, if the diameter B of the pot is smaller than the diameter A of the heating coil 1, the magnetic lines of force will leak from the portion C where the coil part protrudes, which is the difference between them, and will not effectively heat the pot, resulting in poor thermal efficiency. Becomes a source of interference radio waves. Moreover, not only the interference radio waves but also the noise entering the power line may cause terminal voltage to cause malfunction of other equipment connected to the same power supply.

OBJECTS OF THE INVENTION The present invention aims to eliminate leakage magnetic lines of force, suppress interference noise, and improve heat exchange coefficient.

Structure of the Invention In order to achieve the above object, the present invention includes a plurality of adjacent heating coils, an object to be heated such as a pot disposed above the plurality of heating coils, and generation of lines of magnetic force in each of the heating coils. A high frequency power converter,
a control device that detects an inductive coupling state between the heated body and the heating coil and controls energization to each heating coil, the plurality of heating coils consisting of an inner heating coil and an outer heating coil, The control device is configured to energize a heating coil that is inductively coupled to the object to be heated from among the plurality of heating coils. For example, in the case of a large pot, the outer heating coil may also be inductively coupled. Therefore, the control device can energize the inner heating coil and the outer heating coil to heat the entire bottom of the pot. On the other hand, in the case of a small pot, the outer heating coil is not in an inductively coupled state, so the control device energizes the inner heating coil and not the outer heating coil, thereby saving power and preventing radio wave interference. be able to.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention is illustrated in FIGS. 2, 3, and 4.
This will be explained using figures.

FIG. 2A is a top view showing the configuration of the heating coil 1, showing the outer heating coil 1a and the inner heating coil 1.
It is divided into b. FIG. 2B is a cross-sectional view of the same, in which the outer heating coil 1a is placed on the coil base 3.
The heating coil is divided into an inner heating coil 1b and an inner heating coil 1b. Further above there is a top plate 5 on which a pot is placed.

FIG. 3 is a characteristic example showing the relationship between the input current and the coupling coefficient between the pot and the heating coil in FIG. 2, and FIG. 4 is an example of the circuit. The power source 7 is rectified by a rectifier 21 via a switch 8, and a direct current is drawn out to both ends of a smoothing capacitor 20. The outer heating coil 1a and the inner heating coil 1b are connected in series and connected to the resonant capacitor 19 in parallel. This circuit is further connected to an anti-parallel circuit of transistor 18 and diode 17. The output of the current transformer 12 is outputted to the control circuit 14 or the oscillation circuit 16 in accordance with the detection level by the input detection circuit 13. The control circuit 14 drives a contact 15 that short-circuits the outer heating coil 1a.
Furthermore, the oscillation circuit 16 controls the driving of the transistor 18. The control device 11 detects the connection state of the pot and controls the energization of the heating coil, and is constituted by the circuit shown by the dotted line. To explain its operation, if the pot covers the entire heating coil 1, the third
Since the coupling coefficient shown in the figure is 100% or more, 100% of the specified input current flows. Therefore, contact 15 in FIG. 4 remains open and oscillation circuit 16 is approximately
Since the transistor 18 is driven at a cycle of 30 KHz, a high frequency current continues to flow in both the heating coils 1a and 1b.

Next, if the pot 6 is displaced as shown by the dotted line in FIG. 2A, the input current will drop to point X in FIG. 3. The input detection circuit 13 has an F level input current of 98%.
When the temperature is below, the control circuit 14 is driven and the contact 15 is closed. For this reason, the outer heating coil 1a is short-circuited, so a high frequency current flows only through the inner heating coil 1b, and the heating range becomes only the inner heating coil. Since the current point X is below the F level, it will be heated in the above-mentioned state, and magnetic lines of force will not leak from the portion of the outer heating coil 1a that protrudes from the pot 6.

Furthermore, if the pot 6 is shifted or the inner coil 1
For a pan with a diameter smaller than b, the input current in Figure 3 is
It further declines from the point. 80% of the G line is set at a level where the inner heating coil 1b protrudes, but in this case, the input detection circuit 13
detects the input lower limit and prohibits the oscillation circuit 16 from oscillating. Therefore, the drive of the transistor 18 is stopped, and the high frequency current also stops flowing to the inner heating coil 1b, so that heating stops.

When the pot 6 is shifted as described above, the energization range of the heating coil 1 is selected, and if the pot 6 shifts further, heating is stopped. In this way, only the heating coil 1 covered by the pot 6 is energized, so there is no leakage of magnetic lines of force.
Since no interference radio waves are generated and only the heating coil 1 in the portion of the pot 6 is energized, there is no unnecessary loss and efficiency is increased.

In this way, in the case of the present invention, the outer heating coil 1a is short-circuited at the same time as eliminating the leakage of magnetic lines of force that cause interference noise, so that the inner heating coil 1a is short-circuited.
When only b is driven, the short-circuited part acts as a shot ring, and the inner heating coil 1b
The slight leakage of magnetic field lines from the outer heating coil 1
It is possible to obtain the effect of absorbing and further suppressing a.

FIGS. 5 and 6 show other embodiments in which a pan detection device and an input detection circuit are used together.
FIG. 5A is a top view showing an example of the configuration of the heating coil, FIG. 5B is a sectional view thereof, and FIG. 6 is a circuit diagram thereof.

First, in FIGS. 5A and 5B, the heating coil 1 consists of a rectangular outer heating coil 1a for a cooking plate and a circular inner heating coil 1b for a pot.
A central pot detection device 10 is disposed approximately at the center of the pot.
A peripheral pan detection device 22 is arranged around the outer periphery of the heating coil 1 to detect the presence of a pan at four locations 22a to 22d, but 22a to 22d are connected in series and output only when all four locations are detected. Referring to FIG. 6, power source 7 is supplied to the high frequency power conversion circuit via switch 8. As shown in FIG. The power source is rectified by a rectifier 21 and a smoothing capacitor 20 derives direct current. This direct current is applied to a parallel circuit of the inner heating coil 1b and its inner resonant capacitor 19b, and is further connected to the switching semiconductor of the transistor 18b and diode 17b. The smoothing capacitor 20 includes another heating coil 1a on the outer circumferential side, a resonant capacitor 19a on the outer circumferential side thereof, and a transistor 1 as described above.
8a, connected to the diode 17a. Control device 1
1 controls these operations.

To explain its operation, when a rectangular teppanyaki pot that covers the entire heating coil 1 is placed on the top plate 5, both the central pot detection device 10 and the peripheral pot detection device 22 output detection of the presence of the pot. do.
This means that the entire heating coil is inductively coupled to the pot, and first the central pot detection device 10 outputs an output, causing the oscillation circuit 16 to oscillate and drive the transistor 18b at a predetermined period. At the same time, the outer pot detection device 22 also detects the presence of the pot, so the control circuit 14
passes the signal from the oscillation circuit 16 and drives the transistor 18a. Therefore, the outer heating coil 1
A high-frequency current flows through both the heating coil 1b and the inner heating coil 1b, generating lines of magnetic force, and inductively heating the entire rectangular pot.

However, in the case of a circular pot such as an enameled pot, the following operation occurs. For a pot that is slightly larger in diameter than the inner heating coil 1b, only the central pot detection device 10 detects the presence of the pot, and the outer pot detection device 22 does not detect the presence of the pot. Therefore, since the control circuit 14 inhibits the signal from the oscillation circuit 16, the transistor 18a does not operate. Therefore, only the inner heating coil 1b generates magnetic lines of force.

Furthermore, when the diameter is smaller than the diameter of the inner heating coil 1b, the coupling coefficient between the pot and the coil decreases, so as explained in the previous embodiment, the input current decreases as shown in the characteristic example shown in FIG. 5. The input current is detected by a current transformer 12, and an input detection circuit 13 stops the operation of the oscillation circuit 16 when the input current becomes less than a set input lower limit detection level. As described above, in a pot smaller than the inner heating coil 1b and in which leakage of magnetic lines of force occurs, heating is stopped. The pot detection device arranged in this way to detect the presence of a pot and the input detection device to detect the coupling state with the heating coil 1 using input current are used together to select the divided heating coils and control the energization. Therefore, it is particularly suitable for a structure composed of a plurality of irregularly shaped coils as in the present invention. This is because multiple irregularly shaped coils do not provide accurate correlation between the coupling coefficient and the input current.

Furthermore, in this embodiment, the inner heating coil 1b
When heating only the outer heating coil 1a, the transistor 18a, the diode 17a, etc., the operation is stopped, so there is no loss caused by these parts, and the thermal efficiency is improved.

In the plurality of divided heating coils as described above, only the heating coil in which the pot is present is energized, thereby achieving the object of the present invention. The shape of the heating coil, the driving circuit for the heating coil, or the method of detecting the presence of the pot described above is not limited to the embodiments of the present invention.

Effects of the invention (1) Magnetic lines of force are generated only in the area of the heating coil that corresponds to the size of the pot, so all the generated magnetic lines of force act as heating energy for the pot, so there is no leakage of magnetic lines of force, and the diameter of the pot is automatically adjusted. Since it detects and heats, it is easy to use even if the size of the pot is different.

(2) Unnecessary interference noise can be suppressed.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing a conventional example, Figure 2 is an embodiment of the present invention, where A is a plan view, B is a sectional view, and Figure 3 is the relationship between input current and coupling coefficient. 4 is the same circuit diagram, FIG. 5A is a plan view showing another embodiment, B is the same sectional view, and FIG. 6 is the same circuit diagram. 1...Heating coil, 1a...Outer heating coil, 1b...Inner heating coil, 7...Power source, 8
...Switch, 9...High frequency power conversion circuit, 10
...Central pot detection device, 11...Control device, 12...
... Current transformer, 13 ... Input detection circuit, 14 ... Control circuit, 16 ... Oscillation circuit.

Claims (1)

[Scope of Claims] 1. A plurality of adjacent heating coils, a heated object such as a pot disposed above the plurality of heating coils, a high frequency power conversion device that generates magnetic lines of force in each of the heating coils, and A control device that detects an inductively coupled state between the heated body and the heating coil and controls energization of each heating coil, the plurality of heating coils having:
Consists of an inner heating coil and an outer heating coil.
The control device is an induction heating cooker configured to energize a heating coil inductively coupled to the object to be heated from among the plurality of heating coils. 2. The induction heating cooker according to claim 1, wherein the control device detects an input to each heating coil to detect an inductively coupled state between each heating coil and an object to be heated such as a pot.