JP3477956B2 - Control device for induction heating rice cooker - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an induction heating rice cooker used in general households.

[0002]

2. Description of the Related Art In recent years, in order to improve the taste of electric rice cookers, an induction heating method using an inverter, which is expected to produce a strong fire, is taking the lead in place of the conventional sheath heater method. In addition, rice cookers have also been introduced in which heating coils are provided above and below to heat rice alternately so that rice can be wrapped and cooked with strong heat.

[0003]

However, even in such an induction heating type rice cooker, simultaneous energization to both heating coils must be avoided due to the limitation of the current capacity (about 20 amperes) that can be used in general households. Had the problem.

The present invention solves the above-mentioned problems of the prior art, and it can be used within a permissible current range by surely detecting the opening / closing of relay contacts, and can easily improve the quality trouble of the relay. It is intended to provide.

[0005]

A first means of the present invention for solving the above-mentioned problems comprises a unidirectional power supply obtained by rectifying a commercial power supply, a switching element, a resonance capacitor, and a smoothing circuit. An inverter circuit for converting a unidirectional power source into high frequency power, a first heating coil for receiving an output of the inverter circuit, a second heating coil for receiving an output of the inverter circuit, and an output of the inverter circuit for the first Induction heating a first relay connected to the heating coil, a second relay connecting the output of the inverter circuit to the second heating coil, and an oscillation voltage detection circuit that detects the oscillation state of the inverter circuit. In preparation for the control device of the rice cooker, the contacts of the first relay and the second relay are opened to give a drive signal to the inverter circuit, and then the oscillation is performed. The pressure detecting circuit is obtained so as to detect the welding of contacts of the first relay and said second relay.

The second means is a unidirectional power supply obtained by rectifying a commercial power supply, an inverter circuit composed of a switching element, a resonance capacitor, and a smoothing circuit for converting the unidirectional power supply into high frequency power. A first heating coil that receives the output of the inverter circuit, a second heating coil that receives the output of the inverter circuit, a first relay that connects the output of the inverter circuit to the first heating coil, and the inverter A second relay that connects the output of the circuit to the second heating coil, and an oscillation voltage detection circuit that detects the oscillation state of the inverter circuit are provided in the induction heating rice cooker control device, and the first relay or After one of the contacts of the second relay is closed and a drive signal is given to the inverter circuit, the oscillation voltage detection circuit causes the first relay or It is obtained so as to detect the disconnection of the contacts of the second relay.

The third means is to detect the welding of the relay contacts and to provide an open / close signal to the detected relay a plurality of times so as to improve the state of slight welding of the relay contacts.

Further, the fourth means is to detect the non-connection of the relay contacts to give an open / close signal to the detected relay a plurality of times to improve the removal of fine dust between the relay contacts. .

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 is such that, when the contacts of the first relay and the second relay are opened and a drive signal is given to the inverter circuit, the first relay or the second relay. If is operating normally, no voltage will be generated in the oscillation voltage detection circuit because the inverter circuit will not oscillate, but if the contacts of the first relay or the second relay are welded, the inverter circuit will be in the oscillation state. A predetermined voltage is generated in the oscillation voltage detection circuit, and the contact welding state of the first relay or the second relay can be detected.

According to a second aspect of the present invention, when a drive signal is given to the inverter circuit by closing one of the contacts of the first relay or the second relay, a first relay or a second relay is provided. If the relay is operating normally, the inverter circuit will oscillate and a predetermined voltage will be generated in the oscillation voltage detection circuit, but if the contact of the first relay or the second relay is not connected, the inverter circuit will be in the stopped state. Since the oscillation voltage detection circuit does not generate a predetermined voltage, it is possible to detect the non-connection state of the contacts of the first relay or the second relay.

According to the third aspect of the present invention, when the welding of the relay contact is detected, a slight welding state of the relay contact is provided by applying an opening / closing signal to the detected relay a plurality of times to give mechanical vibration to the relay. It will be improved.

According to the fourth aspect of the present invention, when the non-connection of the relay contacts is detected, the relay on the detected side is provided with an opening / closing signal a plurality of times to give mechanical vibration to the relay, so that the relay is caught between the contacts. The non-connection state due to fine dust or the like is improved.

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 shows a first embodiment, in which 1 is a unidirectional power supply composed of a commercial power supply 2 and a rectifying bridge 3, 4 is a smoothing circuit 5 for preventing power line noise due to switching, and resonance. Capacitor 6a, resonance capacitor 6
b, and an inverter circuit composed of the switching element 7,
Reference numeral 8 indicates an inverter drive circuit for controlling the switching element 7, reference numeral 9a indicates a first heating coil connected in parallel to the resonance capacitor 6a to receive the output of the inverter circuit 4,
b is a second heating coil connected in parallel to the resonance capacitor 6b to receive the output of the inverter circuit 4, 10a is a first relay connecting the output of the inverter circuit 4 with the first heating coil 9a, and 10b is an inverter A second relay that connects the output of the circuit 4 to the second heating coil 9b, 11 is a relay drive circuit that independently controls the opening and closing of the first relay and the second relay, and 12 is the oscillation state of the inverter circuit. An oscillating voltage detection circuit for detecting 13 is a microcomputer for controlling the entire rice cooker.

FIG. 2 shows the details of the oscillating voltage detecting circuit. The voltage of the switching element 7 is divided by the voltage dividing circuit 14 and converted into the DC voltage by the peak hold circuit 15, and the comparator 16 uses the reference voltage circuit. It is compared with the reference voltage of 17, and the output is input to the microcomputer 13.

Regarding the operation and action in the above configuration,
It will be described next. In FIG. 1, first, the operation by the induction heating method will be described. When the relay drive circuit 11 closes the contact of the first relay 10a to connect the output of the inverter circuit 4 to the first heating coil 9a and the drive signal is given by the inverter drive circuit 8, the commercial power source 2 and the rectification bridge are connected. The unidirectional power supply 1 formed by 3 is converted into high frequency power by the inverter circuit 4 including the resonance capacitor 6a and the switching element 7 via the smoothing circuit 5, and supplies a high frequency current to the first heating coil 9a. Then, the inner pot (not shown) of the rice cooker whose surface is made of a magnetic material is heated by the principle of induction heating.

Similarly, for the second heating coil, the relay driving circuit 11 closes the contact of the second relay 10b to connect the output of the inverter circuit 4 to the second heating coil 9b. When a drive signal is applied by the circuit 8, the unidirectional power source 1 formed by the commercial power source 2 and the rectifying bridge 3 is converted into high frequency power by the inverter circuit 4 including the resonance capacitor 6b and the switching element 7 via the smoothing circuit 5. Then, a high-frequency current is supplied to the second heating coil 9b. Then, a radiator plate (not shown) formed of a magnetic material inside the outer lid of the rice cooker and arranged so as to face the inner pot is also heated by the principle of induction heating. In this way, rice is cooked by alternately supplying the high-frequency current to the first heating coil 9a and the second heating coil 9b according to the program incorporated in the microcomputer 13.

Details of the oscillation voltage detection circuit will be described with reference to FIG. That is, the contacts of the first relay 10a and the second relay 10b are opened, and the inverter circuit 4
To the inverter circuit 4 if a drive signal is applied to the first relay 10a and the second relay 10b are operating normally.
Cannot oscillate, so that no voltage is generated across the switching element 7. Therefore, the detection voltage formed by the voltage dividing circuit 14 and the peak hold circuit 15 becomes zero volt,
When this is compared with the reference voltage of the reference voltage circuit 17 by the comparator 16, its output becomes "low level", and by determining the input logic of the microcomputer 13 as "low level" as "oscillation stop state", this state is normal. It can be determined that And the first relay 1
If 0a or the second relay 10b is welded, the inverter circuit 4 will be in an oscillating state even if the drive signals are given to the inverter circuit 4 by opening the contacts of the first relay 10a and the second relay 10b. A predetermined voltage is generated across the switching element 7. This is divided by the voltage dividing circuit 14 and converted into a DC voltage by the peak hold circuit 15, and the comparison voltage is compared with the reference voltage of the reference voltage circuit 17 by the comparator 16. The reference voltage should be set lower than the detection voltage in advance. , Its output becomes “high level”, and by determining the input logic of the microcomputer 13 as “oscillation state”, it is judged that this state is abnormal, that is, the relay contact welding state. It is possible. Then, when switching the contact welding detection by this method from the first relay 10a to the second relay 10b, and from the second relay 10b to the first relay 10a
This is done every time when switching to, and if there is any abnormality, the microcomputer 13 can stop the oscillation so that simultaneous energization of the first heating coil 9a and the second heating coil 9b can be avoided.

(Embodiment 2) In FIG. 2, the contact point of the first relay 10a or the second relay 10b is closed to give a drive signal to the inverter circuit 4, and the first relay 10a or the second relay 10a If the relay 10b is normally operating, the inverter circuit 4 normally oscillates, so that a predetermined voltage is generated across the switching element 7. Therefore, when the detection voltage formed by the voltage dividing circuit 14 and the peak hold circuit 15 is compared with the reference voltage of the reference voltage circuit 17 by the comparator 16, its output becomes "high level", and the input logic of the microcomputer 13 becomes "high level".
It is possible to judge that this state is normal by deciding that is the “oscillation state”. Then, even if a closing signal is given to one of the first relay 10a and the second relay 10b, if the relay is in a non-connection state, the inverter circuit 4 is in an oscillating state even if a driving signal is given to the inverter circuit 4. Therefore, a predetermined voltage is not generated across the switching element 7. The output of the comparator becomes "low level", and by determining the input logic of the microcomputer 13 as "non-oscillation state""lowlevel", it is judged that this state is abnormal, that is, the relay contact is not connected. It is possible. Then, the contact non-connection detection by this method is performed every time after switching from the first relay 10a to the second relay 10b and after switching from the second relay 10b to the first relay 10a. This means that the computer 13 can stop the oscillation and notify the abnormality of the control device.

(Third Embodiment) A third embodiment of the present invention will be described with reference to FIG. First, after starting (step 18), an off signal is given to the relay that was on (step 19). Next, it is judged whether or not the relay is off by using the above-mentioned oscillation voltage detection circuit (step 20). If "YES", move to the next step (step 21). If "NO" here, after the open / close signal is given to the relay a plurality of times (step 22), the off signal is given to the relay which has been turned on again (step 23). Then, it is judged again by using the oscillation voltage detecting circuit whether the relay is off (step 24). if"
If "YES", the process proceeds to the next step (step 25). If "NO", the abnormality is notified and the abnormality can be transmitted to the user (step 26). If the relay is abnormal, the relay can be easily restored to normal by applying a switching signal to the relay a plurality of times to apply mechanical vibration.

(Embodiment 4) A fourth embodiment of the present invention will be described with reference to FIG. First, after starting (step 27), an ON signal is given to the relay that has been turned off (step 28). Next, it is judged whether or not the relay is on by using the oscillation voltage detection circuit described above (step 29). If "YES", move to the next step (step 30). If "NO" here, after the open / close signal is given to the relay a plurality of times (step 31), the on signal is given to the relay which has been turned off again (step 32). Then, it is judged again by using the oscillation voltage detecting circuit whether the relay is turned on (step 33). if"
If "YES", the process proceeds to the next step (step 34). If "NO", the abnormality is notified and the abnormality can be transmitted to the user (step 35). In the case of a relay abnormality of a non-connection degree due to trapped fine dust or the like, it is easy to return the relay to a normal state by giving a mechanical vibration by giving an open / close signal to the relay a plurality of times.

Here, the same effect can be obtained by a construction in which a high frequency high voltage transformer is used instead of the second heating coil 9b in combination with a dielectric heating method for driving the magnetron, and the third heating is also used. It goes without saying that the same effect can be obtained with a configuration in which a coil is added.

[0022]

As described above, according to the present invention, the contacts of the two relays are opened and a drive signal is given to the inverter circuit to control the magnitude of the output voltage of the oscillation voltage detection circuit. By comparing, the welding of relay contacts is detected and simultaneous energization to multiple heat sources due to contact welding is avoided, or one of the two relay contacts is closed to drive the inverter circuit. By comparing the magnitude of the output voltage of the oscillation voltage detection circuit, the disconnection is detected by the inclusion of fine dust into the relay contact,
It is possible to provide a control device of an induction heating rice cooker that eliminates troubles such as rice cooking failure due to non-contact connection, and can easily improve relay quality troubles due to slight welding and biting of dust, and its industrial value. Is great.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of a control device for an induction heating rice cooker showing an embodiment of the present invention.

FIG. 2 is a circuit diagram of the oscillation voltage detection circuit of the induction heating rice cooker control device.

FIG. 3 is a flowchart showing the operation of the control device for the induction heating rice cooker.

FIG. 4 is a flowchart showing another operation of the control device for the induction heating rice cooker.

[Explanation of symbols]

1 unidirectional power supply 4 Inverter circuit 9a First heating coil 9b Second heating coil 11 Relay drive circuit 12 Oscillation voltage detection circuit

Front page continuation (72) Inventor Shinichiro Sumiyoshi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Shinichi Sato, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72 ) Inventor Kazunori Kono 1006, Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-5-253054 (JP, A) JP-A-5-258848 (JP, A) JP Hei 5-103717 (JP, A) JP 62-298311 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) A47J 27/00 103 H05B 6/12 313

Claims (4)

(57) [Claims] 1. A unidirectional power supply obtained by rectifying a commercial power supply, an inverter circuit including a switching element, a resonance capacitor and a smoothing circuit for converting the unidirectional power supply into high frequency power, and an output for receiving the inverter circuit. First and second heating coils, first and second relays that connect the output of the inverter circuit to the first and second heating coils, and an oscillation voltage detection circuit that detects an oscillation state of the inverter circuit. Including driving the contacts of the first and second relays to be in an open state, and applying a drive signal to the inverter circuit, and then outputting the first or second by the output of the oscillation voltage detection circuit. Control device for induction heating rice cooker that detects welding of relay contacts. 2. A unidirectional power supply obtained by rectifying a commercial power supply, an inverter circuit including a switching element, a resonance capacitor and a smoothing circuit for converting the unidirectional power supply into high frequency power, and an output for receiving the inverter circuit. First and second heating coils, first and second relays that connect the output of the inverter circuit to the first and second heating coils, and an oscillation voltage detection circuit that detects the oscillation state of the inverter circuit. And driving either one of the contacts of the first or second relay to be in a closed state, and after supplying a drive signal to the inverter circuit, the first or the first by the oscillation voltage detection circuit. A control device for an induction heating rice cooker that detects disconnection of the contact of the second relay. 3. When the welding of the relay contacts is detected, after an open / close signal is given to the relay on the side where the welding is detected a plurality of times,
The control device for an induction heating rice cooker according to claim 1, wherein the welding detection is performed again. 4. The induction device according to claim 2, wherein when the non-connection of the relay contacts is detected, the non-connection detection is performed again after applying the opening / closing signal to the relay on the side where the non-connection is detected a plurality of times. Control device for heating rice cooker.