JP2976798B2 - Control device for induction heating cooker - Google Patents

Abstract

PURPOSE:To provide a control device for an induction heating cooking appliance by which abnormal heating of oil is prevented by accurately detecting a pan whose bottom surface is warped. CONSTITUTION:A temperature detector 8 is installed so as to contact with an under surface of a plate 1 from the center of a heating coil 6, and detects a temperature of a cooking pan 9 placed on an upper surface of the plate 1. A drive circuit 13 is composed of various electronic circuits such as a judging means 14 containing a microcomputer and a control means 15, and takes signals from an operation means 16 and the temperature detector 8 in the judging means 14, and controls current-carrying to the heating coil 6.

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 cooker for preventing abnormal heating of oil.

[0002]

2. Description of the Related Art In recent years, attention has been paid to the fact that induction heating cookers have excellent characteristics such as high efficiency and safety, and the development and production of induction heating cookers have been active. For this reason, the induction heating cooker is designed with particular emphasis on the safety function. An example of a conventional induction heating cooker will be described below.

FIG. 10 is a side sectional view of a conventional induction heating cooker. In FIG. 10, 1 is a plate, and 2 is a frame to which the plate 1 is fixed. The main body case 3 is fixed to the frame 2 and has an intake port 4 on a front surface and an exhaust port 5 on a rear surface. The heating coil 6 is fixed to a coil base 7 by twisting a plurality of conductive wires and winding the wire. The temperature detector 8 is mounted so as to be in contact with the lower surface of the plate 1 from the center of the heating coil 6 and detects the temperature of the cooking pot 9 placed on the upper surface of the plate 1.
The drive circuit 10 supplies power to the heating coil 6. The temperature detector 8 and the drive circuit 10 are electrically connected, and the operation of the drive circuit 10 is controlled by the temperature of the cooking pot 9. The cooling fan 11 is provided near the intake port 4 and cools a heat-generating component in the drive circuit 10 and the like.

The operation of the induction heating cooker configured as described above will be described below. By placing the cooking pot 9 on the plate 1 and turning on a switch of an operation unit (not shown), the heating coil 6 and the drive circuit 10 provided inside the main body can be operated and heated. In addition, when cooking oil in the cooking pot 9 and cooking tempura, if the user continues to heat the oil by mistake, the temperature of the oil will rise abnormally, and in the worst case, the oil will ignite. The drive circuit 10 detects an abnormally high temperature of the temperature detector 8,
When the temperature becomes equal to or higher than a preset control temperature, the current supplied to the heating coil 6 is reduced to perform control for preventing oil ignition. At this time, if the bottom surface of the cooking pot 9 is warped, the temperature of the temperature detector 8 is unlikely to rise.
Oil tends to be abnormally hot. For this reason, when the temperature rise value of the temperature detector 8 per unit time during heating is small, it is determined that the bottom surface of the cooking pot 9 is warped, and correction is performed by making the control temperature smaller than a predetermined value. Was.

[0005]

However, when the bottom of the cooking pot 9 is determined from the temperature rise (temperature gradient) per unit time of the temperature detector 8 during heating as in the above-mentioned conventional example , , It was easy to make a false detection. That is, the temperature gradient of the temperature detector 8 greatly changes depending on factors other than the warpage of the bottom surface of the pot, such as the amount of oil and the heating output, and erroneous detection is likely due to the influence of these factors. Further, the information on the warped state of the bottom surface of the cooking pot 9 has not been actively utilized to improve the tempura cooking.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and provides a control device for an induction heating cooker which accurately detects a pot whose bottom is warped and prevents abnormal heating of oil.
A and purpose.

[0007]

Control device for the induction heating cooker of the present invention to achieve the above Symbol purpose SUMMARY In order to achieve the above, the cooking pot main body
A temperature detector disposed near the contact surface;
Supply of high-frequency power to the heating coil according to the output of the heater
Control means for controlling the temperature of the cooking pot,
Determining means for detecting the state of the
When the heating output is reduced after a predetermined time has elapsed since the start of heating
In both cases, the temperature detected by the temperature detector thereafter becomes maximum.
To detect the state of the bottom of the cooking pot depending on the time
It is.

[0008] If necessary, the bottom of the cooking pot may be warped.
The control temperature for a certain case is higher than the control temperature for no warpage.
If it is set low or there is no warping in the bottom of the cooking pot
Only when judged, the temperature detected by the temperature detector suddenly decreases
The supply of high-frequency power to the heating coil
It is something that was done.

[0009]

According to the above construction , the cooking pot is provided by providing an output reduction period in which the heating output is temporarily reduced or stopped by the drive circuit during heating, and measuring a change in the temperature of the temperature detector during the output reduction period. Can be detected as follows. Since the induction heating cooker directly heats the bottom surface of the cooking pot, the bottom surface of the cooking pot has the highest temperature, and this heat is conducted to heat the temperature detector. Therefore, if the bottom surface of the cooking pot is significantly warped, an air layer is formed between the bottom surface and the outer periphery of the cooking device main body, and heat conduction to the temperature detector is delayed. For this reason, the bottom temperature of the cooking pot becomes the maximum temperature at the start of the heating output reduction, whereas the temperature of the temperature detector reaches the maximum temperature is considerably delayed from that point due to the presence of the air layer. Time indicates the warping state of the bottom of the cooking pot. This means is less likely to affect the magnitude of the heating output or the amount of heated material, because the delay time is mainly affected by the heat conduction with the bottom of the cooking pot, the air layer, and the temperature detector. is there.

Further, when it is determined that the warpage is small , the heating output is controlled at least once with the first control temperature value, and thereafter the heating output is controlled so as not to exceed the set temperature value. When it is determined that the warpage is large, the control is performed at least once with the second control temperature value, and then the heating output is controlled so as not to exceed the set temperature value. As a result, when the warpage of the bottom is small, the temperature of the temperature detector rises in a shorter time than that of the cooked food. This is because the output is controlled before the temperature reaches the control temperature, and the temperature rise of the object to be cooked is delayed. Of course, if the first control temperature is set high as described above in the case where the warpage of the bottom surface is large, the object to be cooked will be heated to an abnormally high temperature, so the initial control temperature will be the first control temperature. The heating output control is performed at a second control temperature lower than the control temperature.

Further, when the bottom of the cooking pot is significantly warped, the temperature of the bottom of the cooking pot is not easily conducted to the temperature detector, so that the temperature change of the bottom of the cooking pot when a new object is introduced. The temperature of the temperature detector follows the response with a large delay, so that there is no
This is to avoid unnecessary use of control.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention. In this embodiment, the same components as those shown in the above-described conventional example are denoted by the same reference numerals, and the description thereof will be omitted. A characteristic configuration of the present embodiment is that a countermeasure for preventing abnormal heating of oil is applied to the drive circuit unit described in the conventional example. That is, the drive circuit 13 is composed of various electronic circuits such as a determination means 14 including a microcomputer, a control means 15 and the like. 6 is controlled. The control circuit 13 has a first control temperature Sh1 set high and a second control temperature Sh1 set low.
The control temperature Sh2 is provided with a set value, and an output reduction period in which the output is stopped during heating is provided, and the difference between the maximum temperature arrival time of the temperature detector and the output stop start time during the output reduction period is detected. If the detection time is shorter than the predetermined determination time, it is determined that the warpage of the bottom surface of the cooking pot 9 is small,
The first output control to the heating coil 6 uses the first control temperature, and the second and subsequent controls are performed at the second control temperature. On the other hand, if the detection time is longer than the predetermined determination time, it is determined that the bottom of the cooking pot 9 is warped greatly, and all controls after the first time are performed at the second control temperature.

Next, the operation will be described with reference to FIGS. 1, 2 and 3. That is, when the drive circuit 13 inputs the start of heating from the operation unit 16, the drive circuit 13 energizes the heating coil 6 with the maximum output, and calculates the integrated output W using the output detection function and the clock function in the drive circuit 13. When the integrated output W becomes equal to or greater than a preset value P, the drive circuit 13 stops supplying power to the heating coil 6, measures the temperature h of the temperature detector 8, and stores it as h1. This energization stop period in which energization is stopped is called an output stop period. This period may be an output reduction period instead of stopping the output and reducing the output. In the output suspension period, the drive circuit 13 always measures the time t from the stop of power supply by using a clock function, and also measures and stores the temperature h of the temperature detector 8 as needed. If the measured value of h2 is equal to or greater than the value initially set to h1, the measured value of h2 is stored again as h1. That is, h1 is set so as to store the current maximum temperature of the temperature detector 8. Also, the time t from the stop of energization is
When the measured value h2 becomes smaller than the maximum temperature value h1 before the preset judgment time T, the temperature detector 8 reaches the maximum temperature within the judgment time T, and the cooking pot 9
Is determined to be small, and the higher first control temperature Sh1 is selected. On the other hand, when the measured value h2 does not become smaller than the maximum temperature value h1 even when the time t from the stop of the power supply becomes longer than the determination time T, the time when the temperature detector 8 reaches the maximum temperature is longer than the determination time T, and the cooking pot 9 is determined to have a large warp, and the lower second control temperature Sh2 is selected. When the maximum temperature value is detected within the determination time T, the power supply is restarted or the output is stopped at the time when the temperature is detected, and the control is performed at least once with the first control temperature value. If the maximum temperature value cannot be detected within the determination time T, the power supply is resumed after the determination time T has elapsed and the second temperature is detected.
Control is started at the control temperature value of. In addition, the first or second
If the maximum temperature is reached within the judgment time T without setting the control temperature value in advance, the first
Can be set. If the maximum temperature is not reached within the judgment time T, the energization is stopped or reduced until the maximum temperature is reached, and the second control temperature value is set in accordance with the maximum temperature arrival time. Can also.

In the practice of the present invention as described above, when the oil is actually heated, a difference is provided in the heating control based on the difference in the degree of warpage of the bottom surface of the cooking pot 9 as shown in FIG. Abnormal heating of oil can be prevented. Here, the reason why the bottom of the cooking pot 9 can be determined based on the maximum temperature arrival time of the temperature detector 8 during the output stop period is as follows. In the induction heating cooker, the bottom surface temperature of the cooking pot 9 becomes the highest, and heat is conducted to the temperature detector 8 from there. However, as shown in FIG. This is because an air layer is formed between the plate 12 and the plate 1, and the larger the warpage of the bottom surface 12, the more the heat conduction to the temperature detector 8 is delayed, and the longer the temperature of the temperature detector 8 becomes the maximum. Since the relationship between the time when the temperature detector 8 reaches the maximum temperature and the warpage of the bottom surface 12 of the cooking pot 9 is hardly affected by the amount of oil in the cooking pot 9 as shown in FIG.

In this embodiment, the first control is controlled by the maximum output or the output stop until the temperature of the temperature detector 8 reaches the control temperature. When the first control temperature is reached, the drive circuit 13 calculates the output to the heating coil 6 based on a combination of the temperature difference between the temperature detector 8 and the control temperature and the temperature gradient of the temperature detector 8 as shown in FIG. The second and subsequent controls are performed. Note that this temperature gradient is calculated in the present embodiment as the time during which the temperature detector 8 changes by 1 ° C.
Further, in this embodiment, the higher control temperature Sh1 is selected only for the first control temperature for which the bottom of the cooking pot 9 is determined to have a small warpage, and the lower control temperature Sh2 is selected for the other control temperatures. . When the bottom surface warp is small, the temperature of the temperature detector 8 rises in a shorter time than that of the oil. This is because the output is controlled in such a way that the temperature rise of the oil becomes slow. Of course, if the first control temperature is set to a high value as described above in the case where the warpage of the bottom surface is large, the oil is heated to an abnormally high temperature, and in this respect, accurate detection of the warpage of the bottom surface of the cooking pot 9 is important. is there.

As described above, according to the control device of the induction heating cooker of the embodiment, the warpage of the bottom surface of the cooking pot 9 can be accurately determined. An abnormally high temperature is prevented, and when the warpage of the bottom surface is small, the first control temperature is increased so that the oil temperature becomes a predetermined temperature in a short time at the beginning of heating. Further, the output suspension period itself of the present embodiment has an effect of preventing abnormal heating of the oil. That is, the longer the warpage of the bottom of the cooking pot 9 is, the longer the output stop period is, during which the temperature rise of the oil is stopped and the temperature of the temperature detector 8 is raised. 8 has the effect of quickly reaching the predetermined control temperature.

FIG. 7 shows a second embodiment of the present invention. The difference from the first embodiment is that the determination of the warpage of the bottom surface of the cooking pot 9 is performed using the temperature gradient (temperature change amount per unit time) of the temperature detector 8 during the output stop period.
When the temperature gradient is equal to or more than a predetermined value, it is determined that the warpage of the bottom surface is small, and when the temperature gradient is smaller than the predetermined value, it is determined that the warpage of the bottom surface is large. That is, during the output suspension period, the drive circuit 13 operates for the time t
Is constantly measured using a clock function, and when the time t becomes equal to or greater than a preset value T, the temperature h of the temperature detector 8 is measured and stored as h2. If h2-h1 is equal to or greater than the preset temperature difference H, it is determined that the warpage of the bottom surface of the cooking pot 9 is small, and the higher control temperature Sh1 is selected. On the other hand, if h2-h1 is smaller than the preset temperature difference H, it is determined that the warpage of the bottom surface of the cooking pot 9 is large, and the lower control temperature Sh2 is selected.

As described above, according to the control device for the induction heating cooker of the second embodiment, the determination of the warpage of the bottom surface of the cooking pot 9 is performed using the temperature gradient of the temperature detector 8 during the output stop period. Therefore, although slightly affected by the amount of oil in the cooking pot 9, the warpage of the bottom surface of the cooking pot 9 can be reduced in a short time without waiting until the maximum temperature of the temperature detector 8 is detected as in the first embodiment. I can judge.

In both the first and second embodiments, the higher control temperature Sh1 is selected only for the first control temperature determined to be small in the warpage of the bottom surface of the cooking pot 9, and the other control temperatures are different. Although the lower control temperature Sh2 is selected, the control temperature after the second time is set to another value Sh3 regardless of the magnitude of the warpage.
It may be. In short, the control temperature may be changed at least once according to the warpage of the bottom surface of the cooking pot 9. In both embodiments, the control for the second and subsequent times is such that the heating output is changed by a combination of the temperature difference between the temperature detector 8 and the control temperature and the temperature gradient of the temperature detector 8. The control may be such that the cutoff temperature and the onset temperature of the heating output are set on the basis of. Further, in both embodiments, the cooking pot 9
Of the bottom surface is divided into two levels, but may be performed in multiple levels. In short, means for determining the bottom curvature during the output suspension period may be used. In both embodiments, the output is stopped during the output stop period. However, the output may be reduced. In short, the output during the output stop period may be smaller than the previous output. Further, various values shown in FIG. 6 are conceivable. In short, the control for calculating the output to the heating coil 6 based on a combination of the temperature difference between the temperature detector 8 and the control temperature and the temperature gradient of the temperature detector 8 is performed. Just do it.

Next, as a third embodiment, a control for improving the performance of the temperature control of the tempura based on the information on the warp state of the bottom surface of the cooking pot 9 will be described. As shown in FIG. 8, even if the temperature is controlled at a predetermined control temperature, the temperature of the temperature detector 8 greatly changes when the bottom surface of the cooking pot 9 is greatly warped.
On the other hand, when the warpage of the bottom surface of the cooking pot 9 is small, the temperature change of the temperature detector 8 is small. In addition, when the food is put in this state, if the warpage of the bottom of the cooking pot 9 is large, the difference between the bottom and the pot before feeding is hard to occur. Almost at the same time, the temperature of the temperature detector 8 decreases, and the difference from the state before the injection is remarkable appears. Therefore, according to the third embodiment, based on the information on the state of warpage of the bottom surface of the cooking pot 9 obtained in the first and second embodiments, etc., when the warpage of the bottom surface is small, the temperature detector 8 When the temperature drops significantly, the drive circuit 13 determines that the food has been put into the cooking pot 9 (this is called load detection), and raises the control temperature for a predetermined time as shown in FIG. Control to recover the reduced amount in a short time.
On the other hand, when the warpage of the bottom surface is large, the control temperature remains fixed. Therefore, when the warpage of the bottom surface is small, the performance of a tempura or the like is improved.
When the bottom has a large warp, the cooking performance is the same as the conventional one. The reason why the control to be used when the warpage of the bottom is large and the warp is small is that the temperature change of the temperature detector 8 is large even in a stable state where no food is contained when the warpage of the bottom is large. This is because the detected load always operates, the stability of the oil temperature is completely lost, and the cooking performance is significantly reduced.

[0022]

As described above, the first to third aspects of the present invention are described above.
According to this, it is possible to provide a control device for an induction heating cooker that accurately detects a pot whose bottom is warped and prevents abnormal heating of oil.

According to the third aspect of the present invention, it is possible to provide a control device for an induction heating cooker in which cooking performance is improved by utilizing the warpage information of the bottom surface of a cooking pot for tempura temperature control. .

[Brief description of the drawings]

FIG. 1 is a block diagram of a control device of an induction heating cooker according to an embodiment of the present invention.

FIG. 2 is a flowchart of a control device of the induction heating cooker according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a control state at an initial stage of oil heating in the embodiment.

FIG. 4 is a sectional view of a main part showing a cooking pot with a warped bottom according to the embodiment of the present invention.

FIG. 5 is a diagram showing a temperature change of a temperature detector during an output stop period.

FIG. 6 is a diagram showing control values of output to a heating coil according to the embodiment of the present invention.

FIG. 7 is a flowchart of a control device for an induction heating cooker according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a temperature change of a temperature detector according to a third embodiment of the present invention.

FIG. 9 is a diagram showing a temperature change when a food to be cooked is put in the third embodiment of the present invention.

FIG. 10 is a sectional view of a conventional heating cooker.

[Explanation of symbols]

 6 heating coil 8 temperature detector 9 cooking pot 13 drive circuit

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tamotsu Izumiya 1006 Kazuma Kadoma, Kazuma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-61-7587 (JP, A) JP-A-4- 36984 (JP, A) JP-A-5-174961 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B 6/12

Claims (3)

(57) [Claims] 1. A cooking pot disposed near a contact surface between a cooking pot and a main body.
A temperature detector and a heating coil according to the output of the temperature detector;
Control means for controlling the state of supply of high-frequency power to the
Judgment means for detecting the warped state of the bottom of a cooking pot as a heating object
And wherein the determination unit determines that a predetermined time has elapsed since the start of the heating.
Reduce the heating output later, and then detect the temperature
The bottom of the cooking pot depends on the time until the detected temperature of the
A control device for an induction heating cooker that detects a warped state of the food. 2. The method according to claim 1, wherein the control means is provided when the bottom of the cooking pot is warped.
Control temperature is lower than the control temperature when there is no warpage.
The control device for an induction heating cooker according to claim 1, wherein 3. The control means, if there is no warping of the bottom of the cooking pot.
Only when judged, the temperature detected by the temperature detector suddenly decreases
The supply of high-frequency power to the heating coil
The control device for an induction heating cooker according to claim 1, wherein