JP3222038B2 - Insulation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat retaining device for keeping a pot warm by induction heating.

[0002]

2. Description of the Related Art For example, a rice cooker using induction heating is:
At the time of rice cooking, the pot is heated by induction heating to cook the rice, and when the rice cooking is completed, the induction heating is temporarily stopped and the steaming operation is performed for a certain period of time, and then the operation shifts to the heat retention. For example, when the temperature drops to less than 72 ° C., the induction heating is restarted to start the heat retaining operation. In the induction heating operation at the time of keeping the temperature, the induction heating operation and the stop of the heating operation are alternately repeated such that the temperature of the pot falls within the allowable temperature range of, for example, 73 ± 3 ° C. .

In the case of performing induction heating, an input current is detected and a drop in load current is detected during the induction heating operation to detect the absence of a pan. When the absence of the pan is detected, the operation is completely stopped.

[0004]

However, when the induction heating is not resumed unless the temperature of the pot is reduced to, for example, less than 72 ° C. when the temperature is shifted from the rice cooking to the heat retention as in the prior art, the temperature is maintained until this temperature is reached. Since induction heating is not performed, the presence or absence of a pan cannot be detected. Therefore, even if the pan was removed while the temperature of the pan was still high immediately after the shift to the heat retention, it was not possible to detect the absence of the pan at that point. In other words, immediately after shifting to heat retention, the temperature in the pot is 100 ° C.
In the vicinity, even if the pan is removed in this state, the ambient temperature of the sensor that detects the pan temperature is maintained at a high state, so the induction heating is immediately restarted and the operation to detect the absence of the pan is not performed. Only when the ambient temperature of the sensor drops below 72 ° C. and the induction heating is restarted, the absence of the pan is detected and the heat keeping operation is stopped.

[0005] As described above, conventionally, when the pot is shifted from the high temperature state to the heat retention, the heat retention operation cannot be immediately stopped even if the pan is removed unless the temperature of the pan falls to the heat retention control temperature. There were inconveniences such as asking the user questions such as breakdown.

Accordingly, the present invention relates to a method of heating a pan to a high temperature state by an induction heating method. In a case where the pan shifts from a high temperature state to a heat retaining state, the pan is removed in a state where the pan temperature does not decrease to a heat retaining control temperature. Provided is a heat retention device that can immediately detect the absence of a pan and stop the heat retention operation even if the occurrence of a pan occurs.

[0007]

SUMMARY OF THE INVENTION The present invention provides a heating means for inductively heating a pot, a temperature detecting means for detecting a temperature of the pot,
Heat insulation control means for performing heat insulation control by repeating the heating operation and heating operation stop of the heating means, and when the pan transitions from a high temperature state to the heat insulation, until the pan falls to a predetermined heat insulation temperature,
Check whether the temperature decrease in the predetermined time of the temperature detected by the temperature detecting means is equal to or higher than the predetermined temperature, and when the temperature decrease is equal to or higher than the predetermined temperature, the heating operation of the heating means and the stop of the heating operation are repeatedly performed to perform the heating operation of the heating means. The presence or absence of a pan is detected, and when the absence of a pan is detected, the heat retaining operation is stopped. When the temperature decrease is lower than a predetermined temperature, the heating operation of the heating means is not performed and the heating operation is stopped. .

[0008]

Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, a case where the present invention is applied to a heat retaining function of a rice cooker will be described. FIG. 1 is a cross-sectional view showing a configuration of a rice cooker. A non-metallic inner frame 2 having a bottomed cylindrical shape is provided inside an outer frame 1 having a U-shaped cross section.
The cooking pot 3 is detachably provided in the inside. The inner frame 2 is
For example, it is made of a polyamide resin containing glass fiber having high heat resistance.

The rice cooker 3 has a two-layer structure in which the inside is made of an aluminum material having excellent heat conductivity, and the outside is made of a ferrous stainless steel which is made of a magnetic metal material and is hard to rust. The inner surface is coated with a non-adhesive PFA resin.

An induction coil 4 for inductively heating the rice cooker 3 and a pan detection sensor 5 for detecting the presence or absence of the rice cooker 3 are arranged outside the bottom of the inner frame 2. In addition, a pot temperature sensor 6 for detecting the temperature of the rice cooker 3 is disposed at the center of the bottom of the inner frame 2 outside.

Inside the bottom of the outer frame 1, there is arranged a circuit board 7 on which circuit elements of an induction heating circuit including an inverter circuit for driving the induction coil 4 are arranged. An intake port 8 is provided below the side of the outer frame 1, and a fan motor 9 is arranged inside the intake port 8 so that cooling air is taken in from the intake port 8.

A lid 10 is provided at the upper opening of the outer frame 1 so as to be openable and closable, and a lid temperature sensor 12 is disposed at a central portion on the upper surface side of a lower plate 11 of the lid 10. Is provided with a lid heater 13. An operation panel 1 provided with various operation switches and indicators on the outer surface of the lid 10.
4 are arranged.

FIG. 2 is a block diagram showing the circuit configuration.
Is a microprocessor provided with a control unit, a calculation unit, a clock unit, and a storage unit. The microprocessor 21 is connected to an input port 22 with an A / D conversion function and an output port 23.

The input port 22 is connected to an operation switch 24 of the operation panel 14, the pan temperature sensor 6, the lid temperature sensor 11, and the pan detection sensor 5, respectively. The output port 23 includes a heater driving unit 25 for the lid heater 13 and a motor driving unit 2 for the fan motor 9.
6. A display drive unit 28 for driving the display 27 of the operation panel 14 and a buzzer drive unit 30 for driving the buzzer 29 are connected respectively.

The output port 23 is connected to a high-frequency current adjusting section 32 of an induction heating circuit 31, and the high-frequency current adjusting section 32 is connected to the induction coil 4. The high-frequency current adjusting unit 32 is configured by an inverter circuit.

The induction heating circuit 31 supplies a predetermined high-frequency current to the induction coil 4 by the high-frequency current adjusting unit 32. As a result, an alternating magnetic field is generated in the induction coil 4.
At this time, if the rice cooker 3 is located at a predetermined position facing the induction coil 4, an eddy current is generated mainly in the magnetic metal material portion of the rice cooker 3, and the eddy current is converted into Joule heat. The pan 3 generates heat.

The pan detection sensor 5 is provided with the induction coil 4.
A high-frequency current adjusting unit 32 for supplying a high-frequency current to the inverter circuit, that is, the input current to the inverter circuit is detected, and when the rice cooker 3 is not at a predetermined position with respect to the induction coil 4, no eddy current is generated. Is reduced, the decrease in the load current is detected to detect the absence of the pan.

At the time of cooking rice, the microprocessor 21
Drives and controls the induction heating circuit 31 to supply a predetermined high-frequency current to the induction coil 4, and to control the high-frequency current adjustment unit 3 based on the temperature detected by the pot temperature sensor 6 and the temperature detected by the lid temperature sensor 11.
2 is controlled.

After the rice cooking operation is completed and a predetermined steaming operation is performed, the operation shifts to a warming operation. At the time of keeping the temperature, the microprocessor 21 drives and controls the induction heating circuit 31 based on FIG.

First, at S1, the pot temperature sensor 6
It is checked whether or not the detected temperature is lower than 72 ° C., and if the detected temperature is 72 ° C. or higher, control is performed during the heat-fall period. Also,
If the detected temperature is lower than 72 ° C., the control of the heat retention stable period is performed. In S2, the operation of the induction heating circuit 31, that is, the induction heating ON control is performed. Then, when the count time in the timer section has elapsed for 2 seconds, the induction heating off control is performed in S3. In this state, when 15 seconds have elapsed in the counting section, the detected temperature of the pot temperature sensor 6 becomes 72 in S4.
Check if it is above ℃.

If the detected temperature is equal to or higher than 72 ° C., the induction heating-off control is further continued for 10 seconds in S5, and it is checked again in S4 whether the detected temperature of the pot temperature sensor 6 is equal to or higher than 72 ° C. I do.

If the detected temperature is lower than 72 ° C., it is further checked in S6 whether the detected temperature of the pot temperature sensor 6 is lower than 70 ° C. And if it is 70 ° C or higher,
After performing the induction heating ON control for 2 seconds in S7, the induction heating OFF control is performed for 15 seconds in S8, and it is checked again whether the detected temperature of the pot temperature sensor 6 is 72 ° C. or more in S4. .

The temperature detected by the pan temperature sensor 6 is 7
If the temperature is lower than 0 ° C., the induction heating on control for 3 seconds is performed in S9, then the induction heating off control is performed for 10 seconds in S5, and the detected temperature of the pot temperature sensor 6 is 72 in S4 again.
Check if it is above ℃.

The above-mentioned control in the heat-reducing period is performed based on FIG. First, induction heating off control is performed in S10, and subsequently, in S11, the pan temperature is detected by the pan temperature sensor 6 and set in a memory in the microprocessor 21.

Subsequently, in S12, it is checked whether or not the pot temperature is lower than 72 ° C. If the temperature is not lower than 72 ° C., the pot temperature check is repeated until 150 seconds have elapsed. Is 72 ° C. or more, the pot temperature is detected by the pot temperature sensor 6 in S13 and set in the memory in the microprocessor 21. Then, in S14,
The temperature difference from the pot temperature detected 150 seconds ago is checked, and it is checked whether the pot temperature has decreased by 10 ° C. or more.

If the pot temperature has not dropped by more than 10 ° C.,
At S16, induction heating off control is performed. That is, the OFF state of the induction heating is maintained, and the process returns to the pot temperature check in S12 again. Also, if the pot temperature drops by 10 ° C or more,
Since there is a possibility that the pot 3 has been removed, the induction heating ON control is performed for one second in S15, and the presence or absence of the rice cooker 3 is detected by the pot detection sensor 5 during this time. When one second has elapsed, the induction heating-off control is performed in S16, and the process returns to the pot temperature check in S12 again.

In the detection of the presence or absence of the pan 3 by the pan detection sensor 5, when the absence of the pan is detected, the microprocessor 21 operates the induction heating circuit 31 and the display 27.
To stop the heat retention display operation and the like. Further, when it is detected in S12 that the pot temperature has become lower than 72 ° C., the processing is shifted to S2 in FIG. That is, the control is shifted to the control of the heat insulation stable period.

In the embodiment having such a configuration, when the rice cooking operation and the steaming operation are completed, the operation shifts to the heat retaining operation.
In the warming operation, first, it is checked whether the temperature of the rice cooker 3 is lower than 72 ° C. Immediately after shifting to the heat retaining operation, the temperature of the rice cooker 3 is high, and in this state, the control of the heat retaining lowering period is performed. That is, the induction heating by the induction heating circuit 31 is turned off, and the pan temperature at this time is detected by the pan temperature sensor 6 and set in the memory in the microprocessor 21.

In this state, while checking whether the pot temperature has dropped below 72 ° C., wait for 150 seconds to elapse,
When 150 seconds have elapsed, the pan temperature at this time is detected by the pan temperature sensor 6 and set in a memory in the microprocessor 21 to determine a temperature difference from the previously set pan temperature. If so, the rice cooker 3 is determined not to be removed, and the induction heating OFF control is maintained.

Then, it waits for 150 seconds to elapse while checking whether the pot temperature has dropped below 72 ° C. again, and when 150 seconds have elapsed, the pot temperature at this time is detected by the pan temperature sensor 6. Then, the temperature is set in the memory in the microprocessor 21 and the temperature difference from the previously set pot temperature is obtained.

In this way, the temperature difference from the previous detection is obtained at intervals of 150 seconds until the temperature of the pot falls below 72 ° C. after the shift to the heat retaining operation. And if the temperature difference is 1
When the temperature becomes 0 ° C. or more, the rice cooker 3 is determined to be possibly removed, and the induction heating is turned on for only one second. 3 is detected.

When it is determined that the rice cooker 3 is present, the induction heating is turned off after one second has elapsed, and the control during the heat retention lowering period is continued. However, when it is determined that the rice cooker 3 is not present, the microprocessor 21 immediately stops the operation of the induction heating circuit 31 and the operation of displaying heat by the display 27 to stop the heat retaining operation.

In this manner, even if the rice cooker 3 is removed in a state where the temperature of the pot is high immediately after shifting from the steaming operation to the heat retaining operation, it is possible to reliably detect this and stop the heat retaining operation. Therefore, if the user takes out the rice cooker 3 immediately after shifting to the heat retaining operation for some purpose, the heat retaining operation is immediately stopped, and the rice cooker 3 is not set. There is no inconvenience that the warming operation is continued.

Further, without removing the rice cooker 3, the control of the temperature lowering period is continued, and the temperature of the rice cooker 3 is eventually reduced to 72.
When the temperature falls below ℃, the control shifts to the control of the heat retention stable period. In the control of the heat retention stable period, after performing the induction heating ON control for 2 seconds, the induction heating OFF control is performed for 15 seconds. Thereafter, if the temperature of the rice cooker 3 is in a range of less than 72 ° C to 70 ° C or more,
The induction heating on control for 2 seconds and the induction heating off control for 15 seconds are repeated and continued.

When the temperature of the rice cooker 3 becomes 72 ° C. or higher, the induction heating off control is forcibly performed for 10 seconds. This is repeated unless the temperature of the rice cooker 3 becomes lower than 72 ° C. After all, the induction heating off control is continuously performed until the temperature of the rice cooking pot 3 becomes lower than 72 ° C.

When the temperature of the rice cooker 3 drops below 70 ° C., the on / off period of the induction heating is changed at this time. That is, induction heating ON control for 3 seconds and induction heating OFF control for 10 seconds are performed, and this is repeated until the temperature of the rice cooker 3 becomes 70 ° C. or higher.

Thus, the temperature of the cooking pot 3 is lower than 72 ° C.
When the temperature is in the range of 70 ° C. or more, the induction heating on control for 2 seconds and the induction heating off control for 15 seconds are repeated, but when the temperature of the rice cooker 3 becomes lower than 70 ° C., the induction heating on control for 3 seconds, The average heating amount is increased by changing the induction heating ON period and the induction heating OFF period such that the induction heating OFF control for 10 seconds is repeated.

Therefore, during the warming operation, when the input voltage decreases and the temperature of the rice cooker 3 becomes lower than 70 ° C., or when the outside air temperature becomes lower and the temperature of the rice cooker 3 becomes lower than 70 ° C.,
Since the average heating amount of the induction heating increases, the temperature of the rice cooker 3 can be prevented from lowering and the temperature of the rice cooker 3 can be maintained in a range of less than 72 ° C to 70 ° C or more.

When the temperature is reduced, the temperature of the rice in the rice cooker 3 is lowered once, and the temperature is again maintained in this state, the induction heating ON control for 2 seconds and the induction heating OFF control for 15 seconds are performed first. Is performed, the operation is switched to the induction heating on control for 3 seconds and the induction heating off control for 10 seconds, and the operation is repeated. In this case, too, the average heating amount of the induction heating increases, and the rice cooker The temperature of 3 is less than 72 ° C to 7
The time required to raise the temperature to 0 ° C. or higher can be shortened.

As described above, when the temperature of the rice cooker 3 is lower than the predetermined heat retention temperature of less than 72 ° C. to 70 ° C. or more, both the induction heating ON period and the induction heating OFF period are switched to reduce the average heating amount. Since the temperature is controlled so as to increase the temperature of the rice cooker 3 so as to always fall within a range of less than 72 ° C. to 70 ° C. or more, a favorable heat retaining operation can be performed.

In the above-described embodiment, in the control during the heat-reducing period, the induction heating is performed for 1 second when the temperature of the pan falling over 150 seconds is 10 ° C. or more to detect the presence or absence of the rice cooker. Time and temperature can be set arbitrarily. However, the rice cooker 3 is set so that the temperature difference used at this time is set to be larger than the temperature decrease immediately after the rice cooker in a state where the minimum amount of heat can be kept in the rice cooker 3. In such a state, it is preferable that the induction heating is not performed as much as possible until the pot temperature falls to below 72 ° C.

The amount of heating at this time, that is, the amount of heating for 1 second on and 150 seconds off, is controlled by keeping the pot temperature in the rice cooker 3 in a state where the minimum amount of rice that can be kept warm is in the heat keeping stable period. Set the heating amount to be less than 72 ° C or less than 70 ° C or more, and turn on for 1 second by mistake, even if the minimum amount of heat that can be kept in the rice cooker 3 is 1
Even if the operation is off for 50 seconds, the rice cooker 3
It is desirable to prevent a situation where the temperature does not drop below 70.degree. C. and above 70.degree.

In this embodiment, the present invention is applied to the heat retaining function of a rice cooker. However, the present invention is not necessarily limited to this.
The present invention can be applied to a heat retaining function of an electric hot plate, an electric pot and the like.

[0044]

As described above in detail, according to the present invention, when a pan is heated to a high temperature state by an induction heating method, when the pan shifts from a high temperature state to a warm state, the pan is immediately removed even if the pan is removed. It is possible to provide a heat retaining device capable of detecting the absence of a pot and stopping the heat retaining operation.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a block diagram of the embodiment.

FIG. 3 is a flowchart showing heat retention control by the microprocessor of the embodiment.

FIG. 4 is a flowchart showing the details of the heat-fall control in FIG. 3;

[Explanation of symbols]

 3 ... Cooking pot 4 ... Induction coil 5 ... Pot detection sensor 6 ... Pot temperature sensor 21 ... Microprocessor 31 ... Induction heating circuit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) A47J 27/00 109 A47J 27/00 103

Claims (1)

(57) [Claims] 1. A heating means for inductively heating a pot, a temperature detecting means for detecting a temperature of the pot, and a heat retention control means for performing a heat retention control by repeating a heating operation and a heating operation stop of the heating means, When the pan shifts from the high temperature state to the heat retention, the temperature of the temperature detected by the temperature detecting means is checked for a predetermined time period for a predetermined time until the temperature of the pan decreases to a predetermined heat retention temperature. When the decrease is equal to or higher than a predetermined temperature, the heating operation of the heating means and the heating operation stop are repeatedly performed to detect the presence or absence of the pan at the time of the heating operation of the heating means, and when the absence of the pan is detected, the heat retention operation is stopped, Further, when the temperature decrease is lower than a predetermined temperature, the heating operation of the heating means is not performed, and the heating operation is stopped, and the stopped state is continued.