JPS59114789A - Induction heating cooking device - 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] 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 form 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.

The heating coil 1 is excited and generates lines of magnetic force to inductively heat a pot 6, which is an object to be heated, placed on a top plate 5. When the pot 6 is removed, the magnet 2 naturally falls due to its own weight, so the microswitch 4 turns OFF [,, High frequency power converter 9
operation will stop and heating will stop. When the pot is placed in this manner, the pot detection device 10 consisting of the magnet 2 and the microswivel 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 only determines whether or not there is a pot on the top plate 5, automatically controls heating, and saves power. The purpose was to bring

Therefore, even if a pot 6 smaller in diameter than the heating coil 1 is placed, the pot detection device 1o works and heats 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 that enters the power line and generates terminal voltage may 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 thermal efficiency.

Structure of the Invention The present invention has a heating coil structure divided into a plurality of parts, and controls the energization of the divided heating coils according to the thickness and shape of the object to be heated, and detects the thickness and shape of the pot. As a method, there is a method using a pot detection device arranged according to the divided shape of the heating coil, a method that detects the inductive coupling state between the pot and the heating coil using an electrical signal, such as an input power level, and a method using a pot detection device. In addition to the device, there are three means of detection based on both the input power level, and the output signals detected by these means are used to energize the divided heating coils in order to energize only the heating coil in the part where the pot is present. ) consists of devices.

DESCRIPTION OF EMBODIMENTS FIG. 2A is a top view showing the arrangement of a plurality of heating coils of the present invention, FIG. 2B is a sectional view thereof, and FIG. 3 is a block diagram thereof. Heating coil 1a on coil base 3
It is divided and arranged by 161. Each heating coil has a pot detection device consisting of a magnet and a microswitch shown in FIG. 1, and the pot detection device 1o2L corresponds to the heating coil 12LK. To explain its operation, when the pan 6 shown by the dotted line in FIG. 2A is placed on the top plate 5, the pan detection devices IC1&, 10b, 10C.

10d detects the presence of the pot, 1oe and 10f do not. Next, referring to FIG. 3, the power supply 7 is switched to the switch 8.
is supplied to the high frequency power conversion circuit 9 via the
is converted to a high frequency. Now, the pot detection device 10iL ~ 10
Contact points 102L to 10 because the presence of the d reed pot is detected.
(1 is closed. The control device 11 selects and energizes the heating coil 1 corresponding to the output of the pot detection device 1o, so only the heating coils 1a to 1d are energized. Therefore, the heating coils 1e and 1f are No magnetic lines of force are generated from a heating coil that is not energized and has no pot 6.In other words, all the generated magnetic lines of force are absorbed by the pot 6.Therefore, there is no leakage of magnetic lines of force, and the heating coil is located in a useless area without a pot. Thermal efficiency can be increased because no electricity is applied to the pan 6.
Although the description has been made for the case of a circular iron plate, since all of the heating coils 121 to 1f generate magnetic lines of force, a good temperature distribution can be obtained with a rectangular iron plate IIAa.

Next, FIGS. 4, 6, and 6 show other examples of actual persimmons, in which the state of inductive coupling between the pot and the heating coil is detected using an input current that is an electrical signal level.

FIG. 4A is a top view showing a proposed configuration of the heating coil 1, which is divided into an outer heating coil 1& and an inner heating coil 1b. FIG. 4B is a cross-sectional view thereof, in which a heating coil divided into 1a and 1b is provided on the coil base 3. Further above there is a top plate 5 on which a pot is placed.

FIG. 6 is a characteristic example showing the relationship between the input current and the coupling coefficient between the pot and the heating coil in FIG. 4, and FIG. 6 is an example of the circuit. Rectifier 21 from power supply 7 via switch 8
The DC current is rectified at both ends of the smoothing capacitor 2o. The heating coils 1a and 1b are connected in series and connected in parallel to a resonant capacitor 19. This circuit further includes transistor 1
8 and a diode 17 in an anti-parallel circuit. The output of the current transformer 12 is outputted to a control circuit 14 or an oscillation circuit 16 in response to a detection level by an input detection circuit 13.

The control circuit 14 drives a contact 16 that short-circuits the heating coil 12L. Furthermore, the oscillation circuit 16 controls the driving of the transistor 18. The control device 11 detects the connection state of the pot and makes the heating coil energized, and is composed of a circuit shown by a dotted line. To explain its operation, when the pot covers the entire heating coil 1, the coupling coefficient shown in FIG. 5 is 100% or more, so a predetermined input current of 10% flows. Therefore, since the contact 15 in FIG. 6 is open and the oscillation circuit 16 drives the transistor 18 at a frequency of about 30 kHz, high frequency current continues to flow through both the heating coils 1a and 1b.

Next, if the pot 6 shifts as shown by the dotted line in Figure 4A,
In the figure, the input current decreases at point X 1. The input detection circuit 13 drives the side leg circuit 14 by 1 and closes the contact 15 when the input current, which is the F level, becomes 98% or less. For this reason, the outer heating coil 1& 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 point X is now below the F level, it will be heated in the above-mentioned state, and magnetic lines of force will not leak from the part protruding from the pot using the outer heating coil.

Furthermore, if the pan shifts or if the pan has a smaller diameter than the inner coil, the input current in FIG. 5 will further decrease from point X.

The 8Q section, which is the G line, is set at a level where the inner coil part just protrudes, but in this case, the input detection circuit 1
3 detects the input lower limit and prohibits the oscillation circuit 16 from oscillating.

Therefore, the driving of the transistor 18 is stopped, and the high frequency current also stops flowing to the inner heating coil 1b, and heating is stopped.

When the pot is shifted as described above, the energization range of the heating coil is selected, and heating is stopped if the pot is shifted further. In this way, only the heating coil that covers the pot is energized, so there is no leakage of magnetic lines of force, and no interference is generated, and since only the heating coil in the area where the pot is energized, there is no unnecessary loss. Higher efficiency.

In this way, in order to eliminate the leakage of magnetic lines of force which are a source of interference noise, in the case of the present invention, the outer heating coil 1& is short-circuited, so when only the inner coil 1b is driven, the short-circuited part is connected to the short ring. As a result, the outer heating coil 13 absorbs a slight leakage of magnetic lines of force from the inner heating coil 1b, thereby achieving the effect of further suppressing the leakage.

FIGS. 7 and 8 show other embodiments in which a pot detection device and an input detection circuit are used together. FIG. 7A is a top view showing an example of the configuration of the heating coil, FIG. 7B is a sectional view thereof, and FIG. 8 is a circuit example.

Heating coil 1 is cooking plate 1 in Figure A and B of the cabinet.
It consists of a rectangular outer heating coil 1a for - and a circular inner heating coil 1b for pots, and a central pot detecting device 1o is disposed approximately at the center of the coil 1. An outer pot detection device 22 is arranged around the outer periphery of the heating coil 1 to detect the presence of a pot at four locations 22a to 22d, but 222L to 22d are connected in series and output only when all four locations are detected. Referring to FIG. 8, 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 the parallel circuit of the inner heating coil 1b and the one-law resonant capacitor 19b, and further connected to the transistor L8b and the diode 17b.
connected to Suinochinda semiconductor. Smoothing capacitor 2
0 is connected to another outer heating coil 1a and its outer resonant capacitor 19a, as well as to a transraster 18a and a diode 17a in the same manner as described above. The control device 11 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 1o 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 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, since the outer pot detection device 22 also detects the presence of the pot, the control circuit 14 passes the signal from the oscillation circuit 16 and drives the transistor IEla. Therefore, a high frequency current flows through both the outer heating coil 1a 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 1o detects the presence of the pot, and the outer pot detection device 22 does not detect it.

Therefore, since the control circuit 14 inhibits the signal from the oscillation circuit 16, the transistor 18& does not operate. Therefore, only the inner heating coil 1b generates magnetic lines of force.

Further, 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. In this way, in a pot smaller than the inner heating coil 1b and in which leakage of magnetic lines of force occurs, heating is stopped. By using the pot detection device arranged in this way to detect the presence of a pot and the input detection device which detects the connection state with the heating coil using input current, it is possible to select the divided heating coils and control the energization. This is especially suitable when the coil is constructed from 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, when only the inner heating coil 1b is heated, the outer heating coil 11L and the transistor 18
Since the operation of i1L, diode 172L7, etc. is stopped, there is no loss generated by these components, and thermal efficiency is increased.

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 thickness of the pot, so all the generated lines of force act as heating energy for the pot, so there is no leakage of lines of magnetic force, and the diameter of the pot can be adjusted automatically. Since it detects and heats, it is easy to use even if the pot size is different.

(2) Unnecessary interference noise can be suppressed0

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a conventional example, FIG. 2 is an embodiment of the present invention, A is a plan view of the main part, B is a sectional view, FIG. 3 is a circuit diagram, and FIG. The figures show other embodiments of the present invention, A is a plan view, B is a cross-sectional view, FIG. 6 is a diagram showing the relationship between the human power current and the coupling coefficient, and FIG. FIG. 7A is a plan view showing another embodiment, FIG. 7B is a sectional view thereof, and FIG. 8 is a circuit diagram showing another embodiment. 1... Heating coil, 7... Power supply, 8.
...Switch, 9...High frequency power conversion circuit, 10...Central pan detection device, 11...
・Side leg device, 12...Current transformer, 13...
・Input detection circuit, 14... Side tilt circuit, 16...
...Oscillation circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 2 1θa 1Oe-10e Figure 3 Figure 4 Figure 5 ) ”Figure 8

Claims (1)

[Scope of Claims] (1) A plurality of adjacent heating coils; an object to be heated such as a pot disposed above the heating coils; a high-frequency power converter that generates lines of magnetic force in each of the heating coils; The control device detects the inductive coupling state between the heated body and the heating coil and controls the energization to the heating coil, and one power switch, and the control device detects the inductive coupling state between the heated body and the heating coil. An induction heating cooker in which electricity is supplied to a heating coil that is inductively coupled to the coil almost entirely. @) The induction heating cooker according to claim 1, wherein the scale control device detects the inductive coupling state between the heating coil and the pot by input, and controls the energization of the heating coil at that level. (3) The control device is equipped with a pot detection device and a lid located at the outer periphery and the center of the heating coil. When the outer pot detection device detects the presence of a pot, the entire heating coil is driven and the center pot detection device is activated. 2. The induction heating cooker according to claim 1, wherein only the divided inner heating coil portion is driven when the presence of a pot is detected.