HK1148896B - Induction heat cooking device - Google Patents

Description

Induction heating cooker

Technical Field

The present invention relates to an induction heating cooker for heating an object to be heated such as a cooking container.

Background

In recent years, induction heating cookers that inductively heat cooking containers such as a boiler and a wok by heating coils have been widely used in kitchens and the like for general households and business use. In an induction heating cooker, a thermistor such as a thermistor is provided under a top plate (top plate), the temperature of the bottom surface of a cooking container is detected by the thermistor, and a heating coil is controlled so that the detected temperature matches a target temperature. For example, when the cooking container is preheated before deep-fry cooking, the temperature detected by the thermistor is controlled to reach the target temperature for preheating.

The temperature rise of the bottom surface of the cooking container is slow when a large amount of oil and food is put into the pot (when the load is large) as in the case of the deep-fry cooking, but is rapid when only a small amount of oil is put into the pot (when the load is small). On the other hand, since the heat sensitive element detects the bottom surface temperature of the cooking container mounted on the top plate by detecting the heat conducted from the cooking container to the top plate, the tracking performance with respect to the bottom surface temperature of the cooking container is not good. Therefore, when the bottom surface temperature of the cooking container rapidly rises, an error between the actual bottom surface temperature of the cooking container and the detection temperature of the thermistor becomes large. Therefore, even if the actual bottom surface temperature of the cooking container reaches the target temperature, the heating may not be continued by detecting the situation, and the bottom surface temperature of the cooking container may far exceed the target temperature and reach a dangerous temperature such as oil ignition temperature. Therefore, some conventional induction heating cookers detect a temperature gradient of the bottom surface of the cooking container, and stop heating when the temperature gradient is steeper than a predetermined temperature gradient, thereby controlling the heating coil so that the temperature of the bottom surface of the cooking container does not reach a dangerous temperature (see, for example, patent document 1).

Patent document 1: japanese laid-open patent publication No. Sho 64-33881

However, in the conventional induction heating cooker that controls the stop of heating based on the temperature gradient calculated based on the detected temperature of the heat sensitive element, when the load is small, for example, when cooking is started by using a cooking vessel having a thin bottom plate and discharging a small amount of oil, a delay in the stop of heating may occur as follows.

Since the heat sensitive element detects the bottom surface temperature of the cooking container by detecting the bottom surface temperature of the top plate, if the gap between the bottom surface of the cooking container and the top plate at the position where the heat sensitive element detects the temperature is large, the relationship between the detected temperature and the actual bottom surface temperature of the cooking container is greatly affected. In particular, in the case of a warped pot bottom, a large gap can occur between the pot bottom and the top plate. In this case, since the temperature of the bottom of the pan is hardly transmitted to the top plate, the temperature gradient calculated from the detection temperature of the heat sensitive element is gentle compared to the actual temperature gradient of the bottom of the pan. Therefore, the stop of heating may be delayed.

In addition, when the bottom surface of the cooking container is thin, the temperature of the bottom surface of the cooking container rises sharply. On the other hand, it takes time for heat to be transferred from the bottom surface of the cooking container to the lower surface of the top plate. Therefore, even if the slope identical to the temperature gradient of the actual bottom surface of the cooking container is successfully detected, a time delay may occur before the detection of the slope, resulting in a delay in the stop of heating.

As described above, in the conventional induction heating cooker, the stop of heating is controlled based on the temperature gradient calculated based on the detection temperature of the induction element, and therefore, the stop of heating may be delayed. When the stop of heating is delayed, there is a problem in that: the temperature of the bottom surface of the cooking container will far exceed the target temperature and then the time required for stabilization to the target temperature becomes long. On the other hand, when the load is small, the conventional induction heating cooker has to start heating with low heating power in order to make the bottom surface temperature of the cooking container not exceed the target temperature. However, in this case, there is a problem that the time required for the bottom surface temperature of the cooking container to reach the target temperature becomes long.

Therefore, the conventional induction heating cooker has the following problems: when the thickness of the bottom plate of the object to be heated is thin, the temperature of the object to be heated cannot be brought to the target temperature in a short time, and an abnormal rise in temperature during transition to the target temperature cannot be prevented. Therefore, when cooking such as stir-frying is performed with a pan, preheating cannot be completed in a short time, and the pan cannot be prevented from being excessively heated and deformed or discolored.

Disclosure of Invention

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an induction heating cooker capable of achieving a target temperature of an object to be heated in a short time and preventing an abnormal increase in temperature in transition to the target temperature even when the bottom surface of the object to be heated has a thin plate thickness. Specifically, it is an object to provide an induction heating cooker: the induction heating cooker can finish preheating in a short time when cooking such as frying is carried out by a pot, and can prevent deformation and discoloration caused by excessive temperature rise of the pot. Further, an induction heating cooker is provided which keeps heating after preheating is completed and keeps the object to be heated at an appropriate temperature.

In order to achieve the above object, an induction heating cooker according to the present invention includes: a top plate made of a material transmitting infrared rays; a heating coil which receives a high-frequency current to inductively heat a cooking container placed on the top plate; an inverter circuit that supplies a high-frequency current to the heating coil; an operation unit including an operation mode setting unit for setting an operation mode of the inverter circuit; an infrared sensor for detecting infrared rays transmitted through the top plate and emitted from the bottom surface of the cooking container; a control unit for controlling the output of the inverter circuit according to the setting input to the operation unit and the output of the infrared sensor; and a notification unit, the operation mode including a preheating mode in which preheating is performed before heating, the control unit performing control as follows: when the operation mode is set to a preheating heating mode, the operation is started in the preheating mode, the cooking container is heated by the 1 st heating output corresponding to the preheating heating mode, when the increment of the output value of the infrared sensor from the start of heating by the 1 st heating output exceeds the 1 st predetermined increment, the notification part is notified that the preheating is completed, and the operation is shifted to a standby mode in which heating is performed by the 2 nd heating output lower than the 1 st heating output.

Instead of the increase in the output value of the infrared sensor from the start of heating with the 1 st heating output, the standby mode may be shifted to when the increase in the output value of the infrared sensor from the predetermined initial output value exceeds the 1 st predetermined increase. In this case, the predetermined initial output value may be an output value of the infrared sensor obtained when the cooking container at a temperature: at this temperature, the gradient of the increase in the output of the infrared sensor with respect to the change in the temperature of the cooking container is equal to or less than a predetermined value.

Can be as follows: in the standby mode, when the increase of the output value of the infrared sensor is equal to or greater than the 2 nd predetermined increase, heating is performed or stopped with the 3 rd heating output smaller than the 2 nd heating output, and when the increase of the output value of the infrared sensor is smaller than the 3 rd predetermined increase equal to or less than the 2 nd predetermined increase, heating is performed with the 2 nd heating output.

The 1 st prescribed increase amount may be variable.

The induction heating cooker may further have: an input current detection unit that detects the magnitude of an input current supplied from a power supply; and a heating coil current detection unit that detects the magnitude of a heating coil current flowing through the heating coil. In this case, the control unit may determine the material of the cooking container based on the detected magnitude of the input current and the magnitude of the heating coil current at the start of the preheating mode, and may set the 1 st predetermined increment based on the determined material of the cooking container.

The induction heating cooker may further have: a buoyancy reducing plate disposed between the top plate and the heating coil; and a temperature detection unit that detects the temperature of the buoyancy reduction plate. In this case, the control unit may set the 1 st predetermined increase amount based on the temperature detected by the temperature detection unit from the start of heating the buoyancy reducing plate with the 1 st heating output.

The induction heating cooker may further have: a buoyancy reducing plate disposed between the top plate and the heating coil; a 1 st temperature detection unit that detects a temperature of the buoyancy reduction plate; and a 2 nd temperature detecting unit that detects the temperature of the top plate. In this case, the control unit may determine whether or not the bottom surface of the cooking container is warped based on a difference between the temperature detected by the 1 st temperature detecting unit and the temperature detected by the 2 nd temperature detecting unit, and may set the 1 st predetermined increment based on the presence or absence of the warp.

The control unit may include an input power integrating unit that integrates input power. In this case, when the increase amount of the output value of the infrared ray sensor from the start of heating at the 1 st heating output does not exceed the 1 st predetermined increase amount, the notification unit is caused to notify that the warm-up is completed and transition is made to the standby mode when the integrated value of the input power from the start of heating at the 1 st heating output integrated by the input power integration unit exceeds the predetermined power integrated value.

The predetermined power integration value may be variable.

The induction heating cooker may further have: an input current detection unit that detects the magnitude of an input current supplied from a power supply; and a heating coil current detection unit that detects the magnitude of a heating coil current flowing through the heating coil. In this case, the control unit may determine a material of the cooking container based on the detected magnitude of the input current and the magnitude of the heating coil current at the start of the warm-up mode, and may set a predetermined integrated power value based on the determined material of the cooking container.

The operation unit may further include a heating power setting unit for allowing a user to instruct a heating power setting of the inverter circuit. At this time, it may be: in the standby mode, when the user inputs an instruction to change the heating power setting through the heating power setting unit, the heating mode is shifted to a 4 th heating output heating mode corresponding to the instructed heating power, and in the heating mode, when the increase in the output value of the infrared sensor exceeds a 4 th predetermined increase, heating is performed or stopped with a 5 th heating output smaller than the 4 th heating output, and when the increase in the output value of the infrared sensor is smaller than a 5 th predetermined increase equal to or smaller than the 4 th predetermined increase, heating is performed with the 4 th heating output.

Can be as follows: when the 4 th heating output is larger than the 2 nd heating output, the 4 th predetermined increase amount is made larger than the 2 nd predetermined increase amount. Can be as follows: when the 4 th heating output is smaller than the 2 nd heating output, the 4 th predetermined increase amount is made equal to the 1 st predetermined increase amount.

The infrared sensor may be disposed halfway in a radial direction of the winding of the heating coil. The infrared sensor may be provided with a silicon photodiode.

According to the heating cooker of the present invention, the infrared sensor can be used to realize the preheating function with good usability. That is, the bottom surface temperature of the cooking container is detected by measuring the output change of the infrared sensor, whereby the actual bottom surface temperature of the cooking container can be accurately detected with good thermal responsiveness. This makes it possible to increase the heating output to reach the target temperature in a short time, and immediately thereafter, to reduce the output to set the temperature suitable for preheating. Therefore, an abnormal increase in temperature in the transition to the target temperature can be prevented. Specifically, a preheating mode for operating the preheating function is provided, and in the preheating mode, the temperature is controlled using the infrared sensor. Therefore, even when cooking such as cooking using a pan, the heating power in the preheating mode can be increased, and preheating can be completed in a short time without damaging the pan. After the completion of the warm-up, the object to be heated can be kept at an appropriate temperature by continuing the heating.

Drawings

Fig. 1 is a block diagram showing a configuration of an induction heating cooker according to embodiment 1 of the present invention.

Fig. 2 is a top view of the top plate of fig. 1.

Fig. 3 is a circuit diagram of the infrared sensor of fig. 1.

Fig. 4 is a characteristic diagram of the infrared sensor of fig. 3.

Fig. 5 is a flowchart showing a schematic operation of an induction heating cooker according to embodiments 1 to 3 of the present invention.

Fig. 6 (a) is a diagram showing an example of a display of the display section when the "preheating heating mode" is selected, (b) is a diagram showing an example of a display of the display section in the preheating mode, (c) is a diagram showing an example of a display of the display section in the standby mode, and (d) is a diagram showing an example of a display of the display section in the heating mode.

Fig. 7 is a flowchart of the warm-up mode.

Fig. 8 is a flowchart of the standby mode.

Fig. 9 is a flowchart of the heating mode.

Fig. 10 (a) is a graph showing the temperature of the cooking container, (b) is a graph showing the amount of increase in the output of the infrared sensor, and (c) is a graph showing heating power.

Fig. 11 is a block diagram showing a configuration of an induction heating cooker according to embodiment 2 of the present invention.

Fig. 12 is a flowchart showing setting of the 1 st predetermined increase Δ V1 in the preheating mode in the induction heating cooker of fig. 11.

Fig. 13 is a block diagram showing another configuration of an induction heating cooker according to embodiment 2 of the present invention.

Fig. 14 is a flowchart showing setting of the 1 st predetermined increase Δ V1 in the preheating mode in the induction heating cooker of fig. 13.

Fig. 15 is a block diagram showing a configuration of an induction heating cooker according to embodiment 3 of the present invention.

Fig. 16 is a flowchart in standby mode according to embodiment 3 of the present invention.

Description of the symbols

1: top board

2: heating coil

2 a: outer coil

2 b: inner coil

3: infrared sensor

4: operation part

4a to 4 f: switch with a switch body

5: commercial power supply

6: rectifying and smoothing part

7: inverter circuit

8: control unit

9: input current detection unit

10: heated object

11: heating part

12: display unit

12 a: operation mode display unit

12 b: fire power display unit

12 c: timing display unit

13: informing part

14: light source

15: heating coil current detection unit

20: timing counting part

31: photodiode

32: operational amplifier

61: full-wave rectifier

62: choke coil

63: smoothing capacitor

71: resonant capacitor

72: diode with a high-voltage source

73: switching element

81: heating control part

82: input power integrating unit

83: material determination unit

Detailed Description

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

EXAMPLE 1

1.1 Structure of Induction heating cooker

Fig. 1 shows a structure of an induction heating cooker according to embodiment 1 of the present invention. The induction heating cooker of the present embodiment has a "preheating function" of preheating to a target temperature before heating with high heating power such as cooking. The induction heating cooker of the present embodiment performs control during preheating and heating by using an output signal of the infrared sensor 3 having good thermal responsiveness in accordance with the temperature of the object 10 to be heated. The induction heating cooker is used by being assembled to a cabinet such as a kitchen.

An induction heating cooker according to embodiment 1 of the present invention includes: a top plate 1 provided above the machine equipment; and a heating coil 2 (an outer coil 2a and an inner coil 2 b) that inductively heats the object 10 to be heated on the top plate 1 by generating a high-frequency magnetic field. The top plate 1 is made of an electrically insulating material such as glass, and is transparent to infrared rays. The heating coil 2 is provided below the top plate 1. The heating coil 2 is concentrically divided into two parts to form an outer coil 2a and an inner coil 2 b. A gap is provided between the outer coil 2a and the inner coil 2 b. The object 10 generates heat in response to the eddy current generated by the high-frequency magnetic field of the heating coil 2.

An operation unit 4 for instructing a user to start/stop heating is provided on the user side of the top plate 1. Display unit 12 is provided between operation unit 4 and object 10. A light source 14 for irradiating the operation unit 4 and the display unit 12 is provided below the operation unit 4 and the display unit 12.

The infrared sensor 3 is provided below the gap between the outer coil 2a and the inner coil 2 b. Since the high-frequency magnetic field of the heating coil 2 is strong at this position, the almost maximum temperature of the bottom surface of the object 10 (output corresponding to the halfway temperature in the radial direction of the cooking container) can be detected. Infrared rays emitted from the bottom surface of the object 10 depending on the temperature of the bottom surface of the object 10 are transmitted through the top plate 1, enter, pass through the gap between the outer coil 2a and the inner coil 2b, and are received by the infrared sensor 3. The infrared sensor 3 detects the received infrared ray and outputs an infrared detection signal 35 based on the amount of the detected infrared ray.

Below the heating coil 2: a rectifying/smoothing unit 6 that converts an ac voltage supplied from the commercial power supply 5 into a dc voltage; and an inverter circuit 7 that generates a high-frequency current upon receiving the supply of the dc voltage from the rectifying/smoothing unit 6 and outputs the generated high-frequency current to the heating coil 2. An input current detection unit 9 for detecting the magnitude of an input current flowing from the commercial power supply 5 to the rectifying and smoothing unit 6 is provided between the commercial power supply 5 and the rectifying and smoothing unit 6.

The rectifying and smoothing unit 6 includes: a full-wave rectifier 61 composed of bridge diodes; and a low-pass filter composed of a choke coil 62 and a smoothing capacitor 63 connected between output terminals of the full-wave rectifier 61. The inverter circuit 7 includes: a switching element 73 (IGBT in the present embodiment), a diode 72 connected in anti-parallel with the switching element 73, and a resonance capacitor 71 connected in parallel with the heating coil 2. The high-frequency current is generated by turning on/off the switching element 73 of the inverter circuit 7. The inverter circuit 7 and the heating coil 2 constitute a high-frequency inverter.

The induction heating cooker of the present embodiment further includes a control unit 8 for controlling the operation of the induction heating cooker. The control unit 8 includes a heating control unit 81, and the heating control unit 81 controls the high-frequency current supplied from the inverter circuit 7 to the heating coil 2 by controlling on/off of the switching element 73 of the inverter circuit 7. The heating control unit 81 controls the on/off of the switching element 73 based on the signal sent from the operation unit 4 and the temperature detected by the infrared sensor 3.

The control unit 8 further includes an input power integrating unit 82 for integrating the input power. The input power integrating unit 82 integrates the input power based on the input current detected by the input current detecting unit 9. For example, the input power integrating unit 82 calculates an integrated value of the input power from the start of warm-up. When the apparent input current is substantially constant, the input power integrating unit 82 may calculate an integrated value of the input power by using the elapsed time. The input power is obtained from the product of the input current and the input voltage, and therefore, the input power can be obtained by measuring the input voltage, but the integrated value of the input power can be more easily calculated from the input current and the elapsed time, depending on the input voltage being constant.

The induction heating cooker of the present embodiment further includes an informing portion 13. The notification unit 13 is, for example, a speaker that outputs an electronic sound. Specifically, the notification unit 13 outputs an electronic sound notifying that the warm-up is completed when the warm-up is completed.

Fig. 2 shows a top view of the top plate 1. At least one (2 in the present embodiment) heating unit 11 indicating a placement position of the object 10 to be heated is printed on the upper surface or the lower surface of the top plate 1. The heating coils 2 are disposed below the heating units 11. A display unit 12 is provided on the front side (user side) of the heating unit 11. The control unit 8 controls the light source 14 to turn on, turn off, and light up characters, illustrations, and the like included in the display unit 12.

The display unit 12 includes: an operation mode display unit 12a showing an operation mode, a heating power display unit 12b showing the magnitude of the output of the heating coil 2, and a timing display unit 12c showing the remaining time of the timing. The operation mode is a setting for controlling the operation of the inverter circuit 7 to be suitable for various cooking (for example, preheating, heating, frying, boiling water, and cooking). The induction heating cooker of the present embodiment includes 5 operation modes including a "preheating mode", a "heating mode", a "frying mode", a "water boiling mode", and a "rice cooking mode", as shown in the left column of table 1 below. When the user selects the "preheating heating mode", the induction heating cooker of the present embodiment operates in the order of "preheating mode" → "standby mode" → "heating mode", as described in detail later.

Selectable modes of operation	Actual mode of operation in selected mode of operation
		Preheating heating mode	Preheating mode → standby mode → heating mode
Heating mode	Heating mode
		Frying mode	Frying mode
Water boiling mode	Water boiling mode
		Cooking mode	Cooking mode

TABLE 1

The operation unit 4 is provided on the front side (user side) of the display unit 12. The operation unit 4 includes a plurality of capacitance type switches 4a to 4 f. The switches 4a to 4f are switches for inputting instructions related to cooking, and are provided in accordance with the number of heating units 11.

Each of the switches 4a to 4f is assigned a specific function. For example, the switch 4a is an off/on switch to which a function of controlling the start and end of cooking is assigned.

The switch 4b is a menu switch to which a function of switching the operation mode to any one of "preheating heating mode", "frying mode", "water boiling mode", and "rice cooking mode" is assigned. By pressing the menu switch 4b, the characters and diagrams in the operation mode display unit 12a are flickered in the order of "heating", "preheating", "frying", "boiling", and "cooking", and the selection of the operation mode is switched. When the operation modes of the "heating mode", "preheating heating mode", "frying mode", "water boiling mode", and "rice cooking mode" are selected, if the off/on switch 4a is operated, the selected operation mode is determined, the display corresponding to the determined operation mode is turned on, and the display corresponding to the operation mode that is not determined is turned off.

The switch 4c is a heating power setting switch to which a function of increasing the heating power is assigned. The switch 4d is a heating power setting switch to which a function of lowering the heating power is assigned. When operating in the "heating mode" or the "standby mode", the heating power can be set by the heating power setting switches 4c and 4 d.

The switches 4e and 4f are timer switches to which a function of setting the heating time is assigned.

When detecting that the switches 4a to 4f are pressed, the control unit 8 controls the inverter circuit 7 based on the pressed switches to control the high-frequency current supplied to the heating coil 2.

Fig. 3 shows a circuit diagram of the infrared sensor 3. The infrared sensor 3 includes a photodiode 31, an operational amplifier 32, and resistors 33 and 34. The resistors 33 and 34 have one end connected to the photodiode 31 and the other end connected to the output terminal and the inverting output terminal of the operational amplifier 32, respectively. The photodiode 31 is a light-sensitive element formed of silicon or the like, and when infrared rays having a wavelength of about 3 μm or less transmitted through the top plate 1 are irradiated thereto, a current flows therein. The photodiode 31 is provided at a position capable of receiving infrared rays emitted from the cooking container. The current generated by the photodiode 31 is amplified by the operational amplifier 32, and is output to the controller 8 as an infrared detection signal 35 (corresponding to the voltage value V) indicating the temperature of the object 10. Since the infrared sensor 3 receives infrared rays emitted from the object 10, thermal response is better than that of a thermistor that detects temperature via the top plate 1.

Fig. 4 shows the output characteristics of the infrared sensor 3. In fig. 4, the horizontal axis represents the bottom surface temperature of an object to be heated 10 such as a cooking container, and the vertical axis represents the voltage value of the infrared detection signal 35 output from the infrared sensor 3. The infrared detection signal 35 has output characteristics 35a to 35c based on the influence of disturbance light. The output characteristic 35a represents an output of the infrared detection signal 35 when no disturbance light is input, that is, only infrared rays emitted from the object 10 are received. The output characteristic 35b represents an output of the infrared detection signal 35 when weak disturbance light is incident on the infrared sensor 3. The output characteristic 35c represents the output of the infrared detection signal 35 when strong disturbance light such as sunlight is incident.

In the present embodiment, the preheating is performed when high thermal power is required for cooking or the like, and therefore the target temperature for the preheating is high (for example, 250 to 270 ℃). Therefore, the output at high temperature can be obtained. Therefore, the infrared sensor 3 of the present embodiment has the following characteristics: as shown in the output characteristic 35a, the infrared detection signal 35 is output when the bottom surface temperature of the object 10 is about 250 ℃. The "no output of infrared detection signal 35" in this case includes not only a case where infrared detection signal 35 is not output at all, but also a case where infrared detection signal 35 is not substantially output, that is, a case where a weak signal is output to the extent that controller 8 cannot actually read a change in the bottom surface temperature of object 10 in accordance with a change in the magnitude of infrared detection signal 35. The output value of the infrared ray detection signal 35 exhibits a nonlinear monotonous increasing characteristic in which the inclination increases more as the temperature of the object to be heated is higher when the range of the output signal, that is, the temperature of the object to be heated 10 is about 250 ℃.

When weak disturbance light is incident on the infrared sensor 3, a signal based on a small value of the disturbance light is output at about below 250 deg.c as shown in the output characteristic 35 b. When strong disturbance light such as sunlight is input, a signal having a large value is output at a temperature lower than about 250 ℃, as shown in the output characteristic 35 c.

In this way, the infrared detection signal 35 output from the infrared sensor 3 is affected by the disturbance light. Therefore, in the present embodiment, whether or not the warming-up is completed, that is, whether or not the object 10 reaches the target temperature is determined based on whether or not the output increase Δ V of the voltage value V of the infrared detection signal 35 exceeds the 1 st predetermined increase Δ V1 from the time of starting the warming-up. The details of the predetermined increments Δ V1 and Δ V2 in fig. 4 will be described later together with fig. 7, 8, and 10.

1.2 actions of Induction heating cookers

Next, the operation of the control unit 8 of the induction heating cooker of the present embodiment configured as described above will be described. Fig. 5 shows a schematic operation of the induction heating cooker of the present embodiment. When the user turns on the power of the induction heating cooker, the user operates the menu switch 4b to select one operation mode from the "preheating heating mode", "frying mode", "water boiling mode", and "rice cooking mode", and then operates the off/on switch 4a to determine the selected operation mode. The operation mode thus determined by the user is input to the control unit 8 via the operation unit 4 (S501). The control section 8 determines whether or not the operation mode determined by the user is the preheating heating mode (S502). If the mode is the preheating heating mode (yes in S502), the control section 8 starts the operation in the preheating mode (S503). In the preheating mode, the temperature of the cooking container is controlled to a predetermined target temperature (preheating temperature). When the temperature of the cooking container reaches the predetermined target temperature and the preheating mode is ended, the control unit 8 starts the operation in the standby mode (S504). In the standby mode, the temperature of object 10 to be heated at the time of completion of preheating is controlled to be maintained until the user sets the heating power. In the standby mode, when the user sets the heating power, the control unit 8 starts the operation in the heating mode (S505). In the heating mode, the inverter circuit 7 is controlled in accordance with the heating power set by the user. If the operation mode determined by the user is not the preheating heating mode (no in S502), the control section 8 determines whether the operation mode determined by the user is the heating mode (S506). If the operation mode determined by the user is the heating mode (yes in S506), the control unit 8 starts the operation in the heating mode without going through the preheating mode and the standby mode (S505). If the operation mode determined by the user is not the heating mode (no in S506), the control unit 8 operates according to the other operation mode selected/determined by the user (S507). For example, if the selected operation mode is the frying mode, the operation in the frying mode is started. In the present embodiment, since the feature exists in the "preheating heating mode", detailed description of the operation modes other than the "preheating heating mode" will be omitted in the following description.

Fig. 6 (a) to (d) show an example of the display unit 12 when the user selects/determines the "preheating heating mode". Specifically, fig. 6 (a) shows a display example when the "preheating heating mode" is selected as the operation mode, fig. 6 (b) shows a display example in the preheating mode, fig. 6 (c) shows a display example in the standby mode, and fig. 6 (d) shows a display example in the heating mode. When the menu switch 4 is operated to select the "warm-up heating mode", characters of "heating" and "warm-up" blink (fig. 6 (a)). In this state, when the off/on switch 4a is operated, the "preheating heating mode" is determined as the operation mode. In the preheating heating mode, preheating is started first from the preheating mode. At this time, the character "heated" is lighted up, and the character "preheated" is flickered (fig. 6 (b)). This indicates that heating is being performed and the warm-up function is operating. Even if the heating power setting switches 4c and 4d are operated during the warm-up, the control unit 8 invalidates the heating power change based on the operation. In order to make it easy for the user to understand that the operation of the fire power setting switches 4c, 4d is invalid, the fire power bar 111 is not displayed on the display section 12 in the warm-up mode.

When the warm-up is completed, a transition is made from the warm-up mode to the standby mode. The control unit 8 receives user operations on the heating power setting switches 4c and 4d in the standby mode. When shifting to the standby mode, the character of "warm up" changes from blinking to illumination, and the fire bar 111 is displayed (fig. 6 (c)). The display of the fire bar 111 at this time corresponds to the fire value at the completion of the warm-up mode. Fig. 6 (c) shows a case where the heating power after the completion of the warm-up mode is "5". The display of the heating power bar 111 indicates to the user that the operation of the heating power setting switches 4c and 4d is effective. After the warm-up mode is completed and the mode shifts to the standby mode, the control section 8 validates the heating power change based on the operation of the heating power setting switches 4c and 4 d. When the user performs the fire setting in the standby mode, the operation shifts to the heating mode. When the mode shifts to the heating mode, the character of "warm up" is turned off, and only the character of "warm up" is in a lit state (fig. 10 (d)).

Fig. 7 shows a flow corresponding to the warm-up mode (S503) of fig. 5. In the warm-up mode, the controller 8 starts warm-up with a predetermined heating power (1 st heating output, for example, 3 kW) (S701). In the preheating mode, the controller 8 controls the temperature of the cooking device to a predetermined target temperature (for example, 250 to 270 ℃). The control unit 8 determines whether or not the heating power setting switches 4c and 4d are operated (S702). When the heating power setting switches 4c and 4d are operated in the warm-up mode (yes in S702), the control unit 8 invalidates the heating power change based on the operation (S703). The control unit 8 determines whether or not the output increase Δ V of the infrared sensor from the start of heating is equal to or greater than the 1 st predetermined increase Δ V1 (S704). When the output increase Δ V of the infrared sensor is equal to or greater than the 1 st predetermined increase Δ V1 (yes in S704), controller 8 determines that object 10 has reached the target temperature for preheating, and causes notifying unit 13 to output an electronic sound for notifying completion of preheating, thereby notifying completion of preheating (S706). The control unit 8 ends the warm-up mode and shifts to the standby mode.

When the object 10 is a shiny metal cooking container such as aluminum, the infrared ray emissivity is very low, and therefore, even if the temperature of the object 10 rises, the output increase Δ V of the infrared ray sensor does not rise immediately. Therefore, in the present embodiment, in order to accurately complete the preheating even when the object 10 is a metal pan, the preheating is completed based on the integrated value of the input power from the start of the preheating. When the output increase Δ V of the infrared sensor is smaller than the 1 st predetermined increase Δ V1 (no in S704), the control unit 8 determines whether the integrated value of the input power from the start of warm-up exceeds a predetermined value (S705). When the integrated value of the input power exceeds a predetermined value (yes in S705), completion of warm-up is notified (S706). If the integrated value of the input power does not exceed the predetermined value, the process returns to step S701.

Fig. 8 shows a flow corresponding to the standby mode (S504) of fig. 5. The control section 8 controls the temperature of the cooking container to be maintained at the temperature at the completion of preheating (for example, approximately 250 ℃) in the standby mode. When the mode is shifted to the standby mode, a fire bar 111 is displayed on the display unit 12 (fig. 6 (c)) so that the user can easily understand that the operation of the fire setting switches 4c and 4d is effective. When the mode shifts to the standby mode, the control section 8 performs heating with a heating power (2 nd heating output, for example, 1 kW) smaller than that in the warm-up mode (S801). In the standby mode, the control unit 8 determines whether or not the heating power setting switches 4c and 4d are operated (S802). When the heating power setting switches 4c and 4d are not operated (no in S802), it is determined whether or not the output increase Δ V of the infrared sensor 3 is equal to or greater than the 2 nd predetermined increase Δ V2, which is greater than the 1 st predetermined increase Δ V (S803). When the output increase Δ V of the infrared sensor 3 is equal to or greater than the 2 nd predetermined increase Δ V2 (yes in S803), the heating power is changed to a value smaller than the 2 nd heating output (the 3 rd heating output, for example, 0 kW) (S804).

The controller 8 determines whether the output increase Δ V of the infrared sensor 3 is smaller than the 3 rd predetermined increase Δ V3 equal to or smaller than the 2 nd predetermined increase Δ V2 (S805). When the output increase Δ V of the infrared sensor 3 is smaller than the 3 rd predetermined increase Δ V3 (yes in S805), the heating power is returned to the 2 nd heating output (S801). When the output increase Δ V of the infrared sensor 3 is not smaller than the 3 rd predetermined increase Δ V3 (no in S805), the heating of the 3 rd heating output is continued.

When the fire setting switches 4c and 4d are operated in the standby mode (yes in S802), the standby mode is ended and the operation shifts to the heating mode.

Fig. 9 shows a flow corresponding to the heating mode (S505) of fig. 5. The control unit 8 controls the heating mode to maintain the temperature corresponding to the heating power set by the user. In the heating mode, heating is started with heating power (4 th heating output) corresponding to the heating power set by the user (S901). The control unit 8 determines whether or not the off/on switch 4a is operated to instruct the end of heating (S902). If termination of heating is not instructed (no in S902), control unit 8 determines whether or not the output increase Δ V of infrared sensor 3 is equal to or greater than the 4 th predetermined increase Δ V4 (S903). When the output increase Δ V of the infrared sensor 3 is equal to or greater than the 4 th predetermined increase Δ V4 (yes in S903), the control unit 8 changes the heating power to the 5 th heating output (for example, 0 kW) having a value smaller than the 4 th heating output (S904).

The controller 8 determines whether or not the output increase Δ V of the infrared sensor 3 is smaller than the 5 th predetermined increase Δ V5 equal to or smaller than the 4 th predetermined increase Δ V4 (S905). When the output increase Δ V of the infrared sensor 3 is smaller than the 5 th predetermined increase Δ V5 (yes in S905), the control unit 8 returns the heating power to the 4 th heating output (S901). When the output increase Δ V of the infrared sensor 3 is not smaller than the 5 th predetermined increase Δ V5 (no in S905), the heating of the 5 th heating output is continued. In the heating mode, when termination of heating is instructed (yes in S902), heating is terminated.

Fig. 10 (a), (b), and (c) show examples of the temperature (° c) of the cooking container, the increase (Δ V) in output of the infrared ray sensor 3, and the heating power (W) in the "preheating mode", "standby mode", and "heating mode" shown in fig. 7 to 9, respectively. The horizontal axis of fig. 10 (a), (b), and (c) represents time. Further, the 1 st to 5 th output increase amounts Δ V1 to Δ V5 in fig. 10 (b) show the output increase amount Δ V of the infrared ray sensor 3 from the start of warm-up.

When the user selects/decides the "preheating heating mode" at time t0, the operation in the preheating mode is started. In the preheating mode, the control portion 8 starts preheating at the 1 st heating output (for example, 3 kW). The warming-up at the 1 st heating output is continued until the output increase Δ V of the infrared sensor 3 reaches the 1 st predetermined increase Δ V1. At time t1, the output increase Δ V of the infrared sensor 3 reaches the 1 st predetermined increase Δ V1. Control unit 8 determines that object 10 has reached the target temperature for preheating, and shifts to the standby mode.

In the standby mode, the controller 8 starts heating with a 2 nd heating output (for example, 1 kW) smaller than that in the warm-up mode (time t1 to t 2). When the heating power is reduced, the temperature distribution of the object 10 is averaged. Therefore, at time t1, the output of infrared sensor 3 provided at a position where the maximum temperature of the bottom surface of object 10 can be detected is temporarily decreased. After that, the output of the infrared sensor 3 increases again. At time t2, the output increase Δ V of the infrared sensor 3 reaches the 2 nd predetermined increase Δ V2 larger than the 1 st predetermined increase Δ V1. The control unit 8 changes the heating power to the 3 rd heating output (for example, 0 kW) smaller than the 2 nd heating output. At time t3, the output increase Δ V of the infrared sensor 3 is smaller than the 3 rd predetermined increase Δ V3 of the 2 nd predetermined increase Δ V2 or less. The control unit 8 returns the heating power to the 2 nd heating output (for example, 1 kW).

In this way, in the standby mode, the following operations are repeated: when the output increase Δ V of the infrared sensor 3 is equal to or more than the 2 nd prescribed increase Δ V2, the heating power is reduced to the 3 rd heating output (e.g., 0 kW), and when the output increase Δ V of the infrared sensor 3 is smaller than the 3 rd prescribed increase Δ V3, the 2 nd heating output (e.g., 1 kW) is restored. By this repeated operation, the temperature of the object 10 is maintained in a temperature range suitable for preheating not lower than the temperature at the completion of preheating (for example, approximately 250 ℃) in the standby mode.

As described above, by detecting the temperature of object 10 based on the increase Δ V in the output of infrared sensor 3 from the heating start point, the influence of the static disturbance light can be suppressed. Further, since the temperature of object 10 is detected based on the output increase Δ V of infrared sensor 3 from the heating start point, preheating can be completed within a temperature range of a degree that can be practically allowed without being greatly affected by the temperature of object 10 at the heating start point, and the temperature of object 10 after completion of preheating can be maintained at an appropriate temperature. That is, even in the case where the temperature of object 10 at the heating start time is a temperature at which the output of infrared ray sensor 3 can be detected (for example, in the case where the temperature is higher than approximately 250 ℃ in fig. 4), the higher the temperature of object 10, the greater the inclination at which the magnitude of the output of infrared ray sensor 3 increases, and the larger the magnitude of the output value increases sharply (in an exponential function), and therefore, the temperature difference of object 10 at the time when the completion of warm-up is detected, which depends on the temperature difference of object 10 at the heating start time, can be suppressed to a degree that can be practically allowed. For example, if the temperature of the cooking container at the heating start time is 267 ℃, the temperature is immediately increased by Δ V1 to complete preheating, and then the temperature is maintained at a temperature not exceeding 274 ℃ (corresponding to Δ V2) (see fig. 4). The temperature at the completion of the warm-up (approximately 267 ℃ C.) and the upper limit value (274 ℃ C.) of the standby mode are temperatures that can be practically allowed.

When the user operates the heating power setting switches 4c and 4d at time t4, the control unit 8 shifts to the heating mode and starts heating at the 4 th heating output corresponding to the set heating power. The values of the 4 th predetermined increase amount Δ V4 and the 5 th predetermined increase amount Δ V5 that is equal to or less than the 4 th predetermined increase amount Δ V4 are determined based on the set 4 th heating output. For example, when the set 4 th heating output is larger than the 2 nd heating output, the 4 th predetermined increase Δ V4 is set to be larger than the 2 nd predetermined increase Δ V2. For example, when the set 4 th heating output is smaller than the 2 nd heating output, the 4 th predetermined increase amount Δ V4 is set to be equal to the 1 st predetermined increase amount Δ V1.

At time t5, the output increase Δ V of the infrared sensor 3 reaches the 4 th predetermined increase Δ V4. The control portion 8 reduces the heating power to the 5 th heating output (for example, 0 kW) smaller than the 4 th heating output. At time t6, the output increase Δ V of the infrared sensor 3 is smaller than the 5 th predetermined increase Δ V5 of the 4 th predetermined increase Δ V4 or less. The control section 8 restores the heating power to the 4 th heating output.

Thus, in the heating mode, such actions are repeated: when the output increase Δ V of the infrared sensor 3 is equal to or greater than the 4 th prescribed increase Δ V4, the heating power is reduced to the 5 th heating output (e.g., 0 kW), and when the output increase Δ V of the infrared sensor 3 is smaller than the 5 th prescribed increase Δ V5, the heating power is returned to the 4 th heating output. By this repeated operation, the object 10 is kept at a temperature corresponding to the set heating power in the heating mode. The operation and effect of the configuration for detecting the temperature of the object 10 based on the output increase Δ V of the infrared sensor 3 from the heating start time in the heating mode are the same as those of the configuration for detecting the temperature of the object based on the predetermined increase Δ V2 described above in the 2 nd paragraph. By setting the 4 th predetermined increase Δ V4 to the increase in the output voltage of the infrared sensor 3 in the range from the start of heating to, for example, approximately 290 ℃.

1.3 summary of

According to the induction heating cooker of the present embodiment, since the temperature of object 10 is detected by infrared sensor 3 having good thermal responsiveness, the actual temperature of object 10 can be accurately detected. For example, even if the bottom surface of the cooking container is warped or the bottom surface of the cooking container is thin, the actual temperature of the object 10 can be accurately detected without a time delay. Therefore, even if the preheating is started with high heating power (1 st heating output, for example, 3 kW), the temperature of the object 10 does not far exceed the target temperature, and it can be quickly detected by the infrared sensor 3 that the temperature of the object 10 reaches the target temperature. Therefore, the warm-up can be started with high fire power. This enables the target temperature to be reached in a short time. Therefore, even when cooking such as cooking that starts cooking with a small amount of oil and high power, preheating before heating can be completed in a short time.

Since the heating power is reduced immediately after the preheating is completed and the mode is shifted to the standby mode, the temperature of the object 10 does not excessively exceed the target temperature at the time of preheating after the preheating is completed. This prevents the object 10 such as a pan from being deformed or discolored due to an excessive increase in temperature.

In the standby mode, the heating power is reduced to the 2 nd heating output to heat, and when the output increase Δ V of the infrared sensor 3 is smaller than the 3 rd predetermined increase Δ V3 equal to or smaller than the 2 nd predetermined increase Δ V2, the heating power is returned from the 3 rd heating output (e.g., 0 kW) to the 2 nd heating output (e.g., 1 kW). Namely, control is such that: even if the temperature after completion of the warm-up changes, the change is immediately detected by the infrared sensor 3, and the temperature after completion of the warm-up is quickly returned. This makes it possible to stabilize the temperature at the completion of the warm-up in a short time. That is, in the standby mode, the temperature after completion of warm-up can be maintained. Therefore, for example, in the standby mode, even if a large amount of food is put into the cooking container and the temperature of the cooking container is lowered, the temperature can be quickly returned to the temperature at the completion of the preheating. Thus, the food in the cooking container can be sufficiently heated, and efficient heating can be achieved when the standby mode is shifted to the heating mode.

Further, since the temperature after completion of the preheating can be maintained, the object 10 can be prevented from being excessively heated. For example, even if a pot with a small amount of oil is heated, the temperature of the pot does not rise sharply in the standby mode. Thus, a safe induction heating cooker can be provided.

In the warm-up mode, control is performed so that the fire power setting is invalidated and an appropriate temperature is automatically reached, and therefore, warm-up to a temperature different from the target temperature for warm-up can be prevented. Further, since the heating power setting is enabled after the completion of the warm-up is notified, the user can start cooking from an appropriate temperature state. Further, the user can change the heating power arbitrarily according to the food material after the completion of the preheating.

Further, by not displaying the fire bar 111 during the warm-up, the user can visually easily understand that the fire change is not possible. Further, by displaying the fire bar 111 when the warm-up is completed, the user can visually recognize that the warm-up is completed and can perform the heating setting. Therefore, the usability is good.

Further, by turning on, blinking, or off the "warm-up" character and the "warm-up" character on the operation mode display portion 12a, the user can visually and easily understand which mode the user is currently operating in. This improves usability. For example, in the warm-up mode, the user can be made aware that the warm-up operation is in progress by lighting up the character "warm-up" and blinking the character "warm-up". After the preheating is completed, the character of preheating is switched from flashing to continuous lighting, so that the user can know that the preheating is completed and the heat preservation state is achieved. When the mode is shifted from the standby mode to the heating mode, the character of "warm up" is turned off, and only the character of "warm up" is turned on, so that the user can be made aware of the end of the standby mode and shift to the heating mode.

In addition, since the silicon photodiode 31 is used as the light receiving element of the infrared sensor 3, the cost of the infrared sensor 3 can be reduced.

The infrared sensor 3 is disposed in the middle of the radial direction of the winding of the heating coil 2, that is, between the outer coil 2a and the inner coil 2b, and measures the bottom surface portion of the object 10 to be heated, which is positioned at the upper portion between the windings of the outer coil 2a and the inner coil 2b, at a position where the high-frequency magnetic field of the heating coil 2 is strong. This enables measurement of a high temperature close to the maximum temperature of the object 10. This makes it possible to control the supply of electric power to the heating coil 2 in a state where the detection sensitivity for the high-temperature portion of the object 10 is higher, and thus, excessive heating can be prevented.

Further, since the warm-up control is performed based on the output increase Δ V of the infrared sensor 3, warm-up can be performed without being affected by disturbance noise such as light.

Further, since the preheating is completed not only by the output increase amount of the infrared sensor 3 but also by the integrated value of the input power, it is possible to prevent overheating and perform appropriate preheating control even in a cooking container having an extremely low emissivity.

According to the present embodiment, the operation modes include the "heating mode" in which the operation mode is switched to the "heating mode" without performing the preheating and the "preheating heating mode" in which the operation mode is switched to the "heating mode" before the heating operation, and therefore, the user can select whether or not to perform the preheating operation, and the usability is further improved.

1.4 modification

When the influence of disturbance light on infrared sensor 3 can be sufficiently suppressed by improving or adding a filter or a light shielding structure, the operation may be shifted to the standby mode in accordance with the increase in the output value of infrared sensor 3 with respect to a predetermined initial output value, instead of the increase Δ V in the output value of infrared sensor 3 from the start of heating with the 1 st heating output. In the case of using a predetermined initial output value, for example, an increase Δ V of the output value of the infrared sensor 3 from an output value (predetermined initial output value) of the infrared sensor 3 measured and stored in advance, which is obtained by placing the cooking container 10 having a low temperature (for example, 35 ℃ or lower) on the top plate 1 so as to cover the infrared sensor 3, may be used: at this temperature, the gradient of the increase in the output of the infrared sensor 3 with respect to the change in the bottom surface temperature of the cooking container 10 is substantially zero or equal to or less than a predetermined value. That is, the predetermined initial output value may be set to a value that is approximately equal to the output value of the infrared sensor 3 obtained when the cooking container 10 is placed on the top plate 1 at a low temperature at which the gradient of the increase in the output of the infrared sensor 3 with respect to the temperature change of the cooking container 10 is equal to or less than a predetermined value. As another example, the output value of the infrared sensor may be measured by using the cooking container 10 as another object having the same emissivity, or by not allowing visible light to enter the infrared sensor 3. The output value of the infrared sensor 3 may be obtained in a situation where an output corresponding to the received light amount of the infrared sensor 3 is not obtained. In this case, the 1 st to 5 th predetermined increase amounts Δ V1 to Δ V5 represent an increase amount Δ V of the output value of the infrared sensor 3 with respect to the predetermined initial output value. The control unit 8 stores a predetermined initial output value in a storage unit (not shown) provided in the control unit 8, and calculates a difference between the output value of the infrared sensor 3 and the predetermined initial output value, thereby easily calculating the increase Δ V of the output value of the infrared sensor 3.

As described in embodiment 1, when the increase Δ V of the output value of the infrared sensor 3 is set to the increase of the output value of the infrared sensor 3 from the start of heating, if the temperature of the cooking container 10 at the start of heating is high, the output sensitivity of the infrared sensor 3 is high, and therefore, when the temperature approaches the target temperature, the temperature at which the output is actually suppressed and controlled becomes higher than the target temperature, and the error with the target temperature becomes large. However, as described above, by setting the increase Δ V of the output value of infrared sensor 3 to the increase of the output value of infrared sensor 3 from the output value of infrared sensor 3 measured in advance and stored at a temperature at which the gradient of the increase of the output of infrared sensor 3 with respect to the change of the bottom surface temperature of cooking container 10 is substantially zero or equal to or less than the predetermined value, it is possible to suppress the error spread in the temperature control for adjusting to the target temperature of cooking container 10.

The 1 st predetermined increment Δ V1 to the 5 th predetermined increment Δ V5 may be changed according to the material or emissivity of the object 10. This enables appropriate temperature control.

In the present embodiment, the standby mode is a mode for maintaining the temperature at the time of completion of warm-up, but the temperature maintained in the standby mode may be a predetermined appropriate temperature lower than the temperature at the time of completion of warm-up. At this time, the 2 nd predetermined increase Δ V2 may be set within a range of the 1 st predetermined increase Δ V1 or less.

In addition, when the object 10 is kept at a high temperature for a long time, the bottom surface of the object 10 may be discolored. To cope with such a situation, the 2 nd heating output after completion of the warm-up may be reduced to, for example, approximately 500W. In this case, after completion of the preheating, the temperature may not be returned to the temperature at the time of completion of the preheating (for example, 180 to 200 ℃). However, in this case, since the function as the preheating function can be still exerted, the 2 nd heating output may be appropriately set.

The values of the 4 th predetermined increase amount Δ V4 and the 5 th predetermined increase amount Δ V5 equal to or smaller than the 4 th predetermined increase amount Δ V4 may be determined regardless of the set 4 th heating output. In this case, the 4 th predetermined increase Δ V4 is also set to be larger than the 2 nd predetermined increase Δ V2. When the set 4 th heating output is larger than the set 2 nd heating output, the following may be set: the 4 th predetermined increase Δ V4 is larger than the 2 nd predetermined increase Δ V2, and the 4 th predetermined increase Δ V4 is smaller as the 4 th heating output is set larger. By increasing the response of temperature suppression when the 4 th heating output is extremely increased, it is possible to prevent an excessive temperature rise of the object to be heated.

When the warm-up mode is ended and the mode shifts to the standby mode, the character of "warm-up" may be turned off.

The notification unit 13 may be a speaker that outputs voice guidance, an LED, a liquid crystal, or the like.

In the present embodiment, the infrared sensor 3 outputs the infrared detection signal 35 at substantially 250 ℃ or higher, but the value is not limited to substantially 250 ℃. For example, a temperature lower or higher than 250 ℃ may be used. However, in consideration of the inexpensive configuration of the infrared sensor 3 and the variation in the circuit of the control unit 8, it is preferable that the temperature be in the range of 240 ℃ to 260 ℃ at the start of the output of the infrared detection signal 35.

The light receiving element of the infrared sensor 3 may be a photodiode or a phototransistor of another type, and a quantum-type infrared sensor may be used as the infrared sensor 3. Further, other types of infrared sensors than the quantum-type infrared sensor, such as a thermopile, may be used.

EXAMPLE 2

In embodiment 2, a case will be described where the 1 st predetermined increase amount Δ V1 is set according to the material quality of the object 10. In the case where the material of the cooking container is a glossy metal cooking container such as aluminum, since the emissivity of infrared rays is extremely low, the output increase Δ V of the infrared ray sensor does not rise immediately even if the temperature of the object 10 to be heated rises. Therefore, in the present embodiment, the 1 st predetermined increase amount Δ V1 is set depending on whether the material of the cooking container is aluminum or not, in order to complete preheating accurately even when the object 10 is a metal pan.

2.1 Structure of Induction heating cooker

Fig. 11 shows a structure of an induction heating cooker according to embodiment 2 of the present invention. The induction heating cooker of the present embodiment has a heating coil current detection unit 15 for detecting the magnitude of a current (referred to as a "heating coil current") flowing through the heating coil 2 in addition to the configuration of fig. 1. The heating coil current detection unit 15 is a current transformer that monitors the heating coil current by magnetically coupling with the heating coil 2. In the present embodiment, the control unit 8 further includes a material determination unit 83, and the material determination unit 83 compares the magnitude of the input current detected by the input current detection unit 9 with the magnitude of the heating coil current detected by the heating coil current detection unit 15, and determines the material of the cooking container based on the ratio of the two.

2.2 Induction heating cooker action

Fig. 12 shows a flowchart for setting the 1 st prescribed increase amount Δ V1. The flow shown in fig. 12 is performed before step S704 in the flow of the warm-up mode shown in fig. 7. When the preheating mode is started, the input current detecting unit 9 detects the magnitude of the input current flowing from the commercial power supply 5 to the rectifying and smoothing unit 6, and the heating coil current detecting unit 15 detects the magnitude of the heating coil current flowing through the heating coil 2 when the switching element 73 is on and the magnitude of the heating coil current as the resonance current flowing through the resonance capacitor 71 and the heating coil 2 when the switching element 73 is off. The material determination unit 83 compares the magnitude of the detected input current with the magnitude of the heating coil current to determine the material of the cooking container (S1201). Specifically, it is determined whether the material of the cooking container is aluminum or another material.

When the heating coil current value corresponding to the input current value is compared, the heating coil current value is larger when the cooking container made of aluminum is heated than when other metal material such as iron or stainless steel is heated. Therefore, it is possible to determine whether the material of the cooking container is aluminum or not based on the detected input current and the heating coil current. The heating control unit 81 determines whether the material of the cooking container determined by the material determination unit 83 is aluminum (S1202). If aluminum is present, the 1 st predetermined increase Δ V1 is set to the increase α (S1203), and if aluminum is not present, the 1 st predetermined increase Δ V1 is set to the increase β (S1204). Here, α < β.

The 1 st predetermined increase Δ V1 thus set is used in step 704 of fig. 7 for comparison with the output increase Δ V of the infrared sensor 3.

2.3 summary of

When the cooking container is made of aluminum, the infrared radiation emission rate is low and the temperature is high for the same emission amount as compared with other metal materials such as iron. Therefore, if the 1 st predetermined increase Δ V1 is made constant, overheating may occur when the material of the cooking container is aluminum. Therefore, in the present embodiment, the material of the cooking container is determined, and when the determined material is aluminum, the 1 st predetermined increase Δ V1 is made smaller than when it is made of other metal such as iron. Thus, even when the cooking container is made of aluminum, excessive heating can be prevented, and the temperature of the cooking container can be prevented from excessively rising. That is, as shown in fig. 7, in order to complete the preheating accurately even when the object 10 is a metal pan, the preheating is completed based on the integrated value of the input power from the start of the preheating (yes in S705), and therefore it is safe, but like this embodiment, the 1 st predetermined increment Δ V1 is set based on the material of the cooking container, and in the case of the material having a high emissivity, the 1 st predetermined increment Δ V1 is set to be lower than that in the case of the material having a low emissivity, and therefore the preheating mode can be completed with higher accuracy, and the heating can be realized more safely and efficiently. According to the present embodiment, even when the material of the cooking container is aluminum, the temperature of the bottom surface of the cooking container can be detected instantaneously with high accuracy, and when the temperature of the bottom surface reaches a predetermined temperature, the heating power is instantaneously limited to keep the temperature, and efficient heating with improved safety can be realized. In this way, even when the temperature rise tendency of the bottom surface varies depending on the material of the cooking container, the temperature can be controlled depending on the material, and the heating power can be restricted to keep the temperature when the temperature of the bottom surface reaches a predetermined temperature, thereby realizing efficient heating with improved cooking performance and safety.

In the present embodiment, the 1 st predetermined increase Δ V1 is changed depending on whether the material is aluminum (for example, whether it is aluminum or iron is determined), but the 1 st predetermined increase Δ V1 may be changed in accordance with the emissivity of the material so that the 1 st predetermined increase Δ V1 of the material having a large emissivity is smaller than the 1 st predetermined increase Δ V1 of the material having a small emissivity, for other materials, and the same effect can be obtained.

The increments α and β set as the 1 st predetermined increment Δ V1 may be variable. Thus, even when the material of the cooking container to be heated or the amount of warpage of the bottom surface of the cooking container exceeds expectations, appropriate temperature control can be performed, and efficient heating with improved safety can be achieved.

2.4 modification example

Fig. 13 shows an induction heating cooker provided with a buoyancy reducing plate that reduces buoyancy acting on a cooking container. The induction heating cooker shown in fig. 13 further includes, in addition to the configuration of fig. 11: a buoyancy reducing plate 16 provided between the top plate 1 and the heating coil 2; and a 1 st temperature detecting portion 18 (e.g., a thermistor) that detects the temperature of the buoyancy reducing plate 16. In the case where the cooking container is made of aluminum, since buoyancy is generated, as shown in fig. 13, a buoyancy reducing plate 16 (for example, a plate made of a conductive material such as aluminum having a thickness of 0.5 to 1.5 mm) for reducing buoyancy acting on the cooking container may be provided between the top plate 1 and the heating coil 2. The buoyancy reducing plate 16 is provided in an annular shape when viewed from above, covers the heating coil 2, and increases the equivalent series resistance of the heating coil 2, thereby reducing the current of the heating coil 2 required to obtain a desired heating output and reducing the buoyancy acting on the cooking container. In addition, the buoyancy reducing plates 16 may be arranged in a divided manner. When the buoyancy reducing plate 16 is provided between the top plate 1 and the heating coil 2, the buoyancy reducing plate 16 is heated by the heating coil 2 to a high temperature. At this time, the infrared rays emitted from the buoyancy reducing plate 16 are reflected in the top plate 1 and enter the infrared sensor 3, and the top plate 1 reaches a high temperature and the infrared rays from the top plate 1 enter the infrared sensor 3. That is, since the infrared sensor 3 detects the high temperature of the buoyancy reducing plate 16, the bottom surface temperature of the cooking container cannot be accurately detected. Therefore, in this example, the 1 st fixed increase Δ V1 is changed depending on whether or not the buoyancy reducing plate 16 is at a high temperature (for example, 350 ℃ or higher) equal to or higher than the predetermined temperature. Fig. 14 shows an operation of setting the 1 st predetermined increment Δ V1 in the induction heating cooker of fig. 13. In fig. 14, steps S1401, S1402, and S1406 are the same as steps S1201, S1202, and S1204 of fig. 12, respectively, and therefore, the description thereof is omitted. In fig. 14, when it is determined that the material of the cooking container is aluminum (S1402), the control unit 8 determines whether or not the temperature of the buoyancy reducing plate 16 detected by the 1 st temperature detecting unit 18 is equal to or higher than a predetermined temperature (e.g., 350 ℃) (S1403). If the temperature is equal to or higher than the predetermined temperature, it is determined that the temperature of the buoyancy reducing plates 16 is high, and the 1 st predetermined increase Δ V1 is set to the increase α 1 (S1404). If the temperature is not higher than the predetermined temperature, it is determined that the temperature of the buoyancy reducing plates 16 is not high, and the 1 st predetermined increase Δ V1 is set to the increase α 2. Here, α 1 < α 2. When the buoyancy reducing plate 16 is at a high temperature equal to or higher than the predetermined temperature, the 1 st predetermined increase Δ V1 is made smaller than when the temperature is lower than the predetermined temperature, so that even if the trend of the temperature rise of the bottom surface of the cooking container after the start of heating is affected by the temperature of the buoyancy reducing plate at the start of heating, the temperature rise of the bottom surface of the cooking container can be accurately detected, and the temperature of the cooking container is prevented from rising excessively, thereby improving safety.

In addition, as exemplified by the object to be heated 10 in fig. 13, in the case of a cooking container made of aluminum, a bottom surface of the cooking container may be warped inward (dented). At this time, the infrared sensor 3 cannot accurately detect the bottom surface temperature of the cooking container. Therefore, the 1 st predetermined increase Δ V1 may be changed depending on whether or not the bottom surface of the cooking container is warped. At this time, as shown in fig. 13, a 2 nd temperature detecting unit 17 (for example, a thermistor) for detecting the temperature of the top plate 1 is further provided. The 2 nd temperature detector 17 is disposed at a position corresponding to the central portion of the heating coil 2, and detects the temperature of the top plate 1. In this case, the induction heating cooker also operates according to the flow of fig. 14. However, instead of the processing of step S1403 of fig. 14, the following processing is performed: the control unit 8 determines whether or not the difference between the temperature of the top plate 1 detected by the 1 st temperature detection unit 18 and the temperature of the buoyancy reducing plate 16 detected by the 2 nd temperature detection unit 17 is equal to or lower than a predetermined temperature (for example, 50 ℃) after a predetermined time (for example, 10 seconds) has elapsed from the start of heating, and thereby determines whether or not the bottom surface of the aluminum cooking container is warped. If the temperature difference is equal to or less than the predetermined temperature, it is determined that the bottom surface of the cooking container is warped, and the 1 st predetermined increase amount Δ V1 is set to the increase amount α 1 (S1404). If the temperature difference is less than the predetermined temperature, it is judged that the bottom surface of the cooking container is not warped, and the 1 st predetermined increment Δ V1 is set to the increment α 2 (S1405). Here, α 1 < α 2 < β. Accordingly, even when the floating force reduction plate is induction-heated to a high temperature due to the warp of the bottom surface of the aluminum cooking container at the start of the warm-up mode and the infrared sensor 3 cannot accurately detect the temperature of the bottom surface of the cooking container, the 1 st predetermined increase Δ V1 is set according to the presence or absence of the warp, and thus it is possible to accurately detect that the temperature of the bottom surface of the cooking container has reached the predetermined temperature. This prevents the temperature of the cooking container from rising excessively, improves cooking performance, and enables safe and efficient heating.

The predetermined power integrated value in S705 in fig. 7 may be changed according to the material of the cooking container. In the case of a cooking container having a good thermal conductivity and poor thermal efficiency, such as an aluminum cooking container, the temperature of the cooking container corresponding to the input integrated value is lower than that of other materials due to heat loss. Therefore, it is preferable to set the predetermined power integrated value to be larger for the material other than aluminum (that is, the predetermined power integrated value P1 for the material other than aluminum > the predetermined power integrated value P2 for the material other than aluminum). Thus, even when a cooking container having a very low emissivity is heated, appropriate temperature control can be achieved, and even when the magnitude of input power differs depending on the material of the cooking container, high-precision temperature control can be achieved. The predetermined power integrated values P1 and P2 may be variable. Thus, even when the magnitude of the input power depending on the material of the cooking container is beyond expectations, appropriate temperature control can be achieved, and efficient heating can be achieved. The predetermined power integrated value in S705 in fig. 7 may be set according to whether the buoyancy reducing plate 16 is at a high temperature or according to whether the bottom surface of the cooking container is warped.

The heating coil current detection unit 15 may be any member capable of detecting the magnitude of the heating coil current, and may be capable of detecting a voltage or a current proportional to the magnitude of the heating coil current, such as the voltage of the resonant capacitor 70 or the voltage or the current of the switching element 73. The input current detection unit 9 is a current transformer in embodiments 1 and 2, but is not limited to this, and for example, a shunt resistor having a minute resistance value of 0.1 to 10m Ω (milliohm) may be connected to the input current path, and the magnitude of the input current may be measured from the voltage drop. The material determination unit 83 is not limited to the above configuration, and may be configured to determine the material of the cooking container.

As described above, according to the induction heating cooker of the present embodiment, the temperature of the cooking container can be detected with high accuracy and the temperature of the cooking container can be maintained accurately without being affected by the difference in infrared radiation rate due to the material of the cooking container, the temperature of the buoyancy reducing plate at the start of heating, and the warping of the bottom surface of the cooking container. This can prevent an excessive temperature rise. Therefore, the induction heating cooker of the present embodiment is useful for applications such as induction heating cookers used in kitchens and businesses of general households.

EXAMPLE 3

In embodiment 3, an induction heating cooker capable of heating without adversely affecting a cooking container will be described. When the cooking container is heated for a long time, discoloration and deterioration (for example, deterioration of the coated fluororesin) occur. Therefore, in embodiment 3, when the user does not perform cooking or forgets to turn off the switch, or does not perform the switch operation for a long time, the heating is stopped. Specifically, in the standby mode, when a predetermined time has elapsed without the user operating the switch, the heating is stopped. Thereby, discoloration and damage of the cooking container are prevented.

Fig. 15 shows a structure of an induction heating cooker according to embodiment 3 of the present invention. The induction heating cooker of the present embodiment further includes a timer counting unit 20 in addition to the configuration of fig. 1. The timing counting unit 20 measures a time (referred to as "timing time") from the start of the operation in the standby mode, and transmits a heating stop signal to the control unit 8 when the timing time reaches the 1 st predetermined time.

Fig. 16 shows an operation of the induction heating cooker of the present embodiment in the standby mode. Fig. 16 shows a flow related to a function of stopping heating when the switch operation is not performed for a long time. The operation shown in fig. 16 is performed in parallel with the operation related to the heating control shown in fig. 8. When the mode is shifted from the warm-up mode to the standby mode, the timer counting unit 20 starts counting the timer period (S1601). At this time, the time (1 st predetermined time — timer time) from the stop of heating is displayed on the timer display unit 12 c. The control unit 8 determines whether or not the heating power setting switches 4c and 4d have been operated (S1602). When the heating power setting switches 4c and 4d are operated (yes in S1602), the timer counting unit 20 stops counting (S1603). After that, the standby mode is ended, and the operation shifts to the heating mode.

When the heating power setting switches 4c and 4d are not operated (no in S1602), the control unit 8 determines whether or not the 1 st predetermined time (for example, 5 minutes) has elapsed since the timer count unit 20 (S1604). When the 1 st predetermined time has elapsed after the timer time, the control unit 8 causes the notification unit 13 to input a sound notifying that heating is to be stopped (S1605). For example, a sound of "stop heating" is output. After that, the control unit 8 stops heating (S1606). If the timing time has not elapsed for the 1 st predetermined time (e.g., 5 minutes), it is determined whether or not the 2 nd predetermined time (e.g., 3 minutes) shorter than the 1 st predetermined time has elapsed (S1607). If the timing time passes the 2 nd predetermined time, the alarm 13 outputs a sound for prompting the user to cook. For example, a sound of "please start cooking" is output. If the timing time has not elapsed the 2 nd prescribed time, the process returns to step S1602.

When the user does not perform the operation after the completion of the preheating, the heating is stopped, whereby the adverse effect on the cooking container, specifically, the discoloration and damage of the cooking container can be prevented.

By outputting a sound for prompting the start of cooking before the stop of heating, the user can be prompted to start cooking by inserting the food material before the stop of heating. This makes the user comfortable. Further, by outputting a sound for notifying the stop of heating when the heating is stopped, the user can be informed that the heating is stopped.

In the standby mode, when the heating power setting switches 4c and 4d are operated, the heating is continued while the count of the timer time is stopped, and thus the cooking can be continued when the user wants to cook. This makes the user comfortable.

In the standby mode, the remaining time until the heating is automatically stopped is displayed on the timing display unit 12c, whereby the user can visually and easily know the remaining time until the heating is completed. This can prompt the user to cook.

In the present embodiment, the heating is stopped in step S1606, but the heating output may be switched to a heating output smaller than the heating output at this time, instead of stopping the heating. In this case, the same effects as those of the present embodiment can be obtained.

In step S1602 of the present embodiment, the case where the heating power setting switches 4c and 4d are pressed has been described, but any switch other than the heating power setting switches 4c and 4d may be used. For example, in S1602, when the time switches 4e and 4f are pressed, the same operation as that of the present embodiment may be performed.

Note that the sound output for prompting the start of cooking in S1608 may be performed only once after the 2 nd predetermined time elapses from the timer time, or may be repeated at predetermined intervals (for example, every 30 seconds).

In addition, it may be: when the user presses a predetermined switch disposed in the operation unit 4 while the timer time reaches the 1 st predetermined time, the count value of the timer time is reset to start counting again, and when the timer time reaches the 3 rd predetermined time (for example, 10 minutes) longer than the 1 st predetermined time (for example, 5 minutes), the heating is stopped. Thus, even if the user forgets to turn off the heating after performing an operation for a while in order to cook, the heating can be automatically stopped, and the safety can be improved.

In the present embodiment, the operation in the standby mode is described, but in the heating mode, when the user does not operate the switch for a long time, the heating output may be set to be smaller than the heating output so far or the heating may be stopped. For example, it may be: the timing counter 20 measures the time from the transition to the heating mode, determines whether or not the measured time has elapsed for a 4 th predetermined time (for example, 45 minutes) between step S901 and step S902 in fig. 9, and sets the heating output to be smaller than the heating output so far or stops the heating when the predetermined time has elapsed. This can prevent discoloration and deterioration of the object to be heated (for example, deterioration of the fluororesin applied). The 1 st predetermined time in the standby mode is preferably set to be shorter than the 4 th predetermined time in the heating mode.

According to the induction heating cooker of the present embodiment, when the user does not perform the operation after the completion of the warm-up, the heating is stopped before the cooking container is discolored or damaged, and the heating can be performed without adversely affecting the cooking container.

The induction heating cooker of the present invention can complete preheating in a short time and maintain the temperature after completion of preheating in a small load, and is therefore very useful for an induction heating cooker used in general households, restaurants, and the like, in which cooking is performed.

Claims (15)

1. An induction heating cooker, characterized by comprising:

a top plate made of a material transmitting infrared rays;

a heating coil that receives a high-frequency current to inductively heat the cooking container placed on the top plate;

an inverter circuit that supplies a high-frequency current to the heating coil;

an operation unit including an operation mode setting unit for setting an operation mode of the inverter circuit;

an infrared sensor for detecting infrared rays radiated from a bottom surface of the cooking container and transmitted through the top plate;

a control unit that controls an output of the inverter circuit based on a setting input to the operation unit and an output of the infrared sensor; and

a notification unit for notifying the user of the presence of the user,

the operation modes include a preheating heating mode in which preheating is performed before heating is performed,

the control unit performs the following control: when the operation mode is set to the preheating heating mode, the operation is started in the preheating mode, the preheating mode heats the cooking container by using the 1 st heating output corresponding to the preheating heating mode, when the increment of the output value of the infrared sensor after the heating is started by using the 1 st heating output exceeds the 1 st predetermined increment, the informing part informs that the preheating is finished, and the operation is shifted to the standby mode of heating by using the 2 nd heating output lower than the 1 st heating output.

2. The induction heating cooker according to claim 1,

the infrared sensor has the following characteristics: an infrared detection signal is outputted when the temperature of the cooking container is higher than a predetermined temperature, and the infrared detection signal is not outputted when the temperature of the cooking container is lower than the predetermined temperature,

and the output value of the infrared sensor exhibits a nonlinear monotone increasing characteristic in which an inclination increases more as the temperature of the cooking container increases when the temperature of the cooking container is equal to or higher than the predetermined temperature,

shifting to the standby mode when an increase in the output value of the infrared ray sensor from a predetermined initial output value exceeds the 1 st predetermined increase amount instead of the increase in the output value of the infrared ray sensor from the start of heating with the 1 st heating output,

the predetermined initial output value is an output value of the infrared sensor obtained when the cooking container at a temperature: at this temperature, the gradient of the increase in the output of the infrared sensor with respect to the change in the temperature of the cooking container is a predetermined value or less.

3. The induction heating cooker according to claim 1 or 2,

in the standby mode, when the increase of the output value of the infrared sensor is equal to or greater than the 2 nd predetermined increase, heating is performed or stopped with the 3 rd heating output smaller than the 2 nd heating output, and when the increase of the output value of the infrared sensor is smaller than the 3 rd predetermined increase equal to or less than the 2 nd predetermined increase, heating is performed with the 2 nd heating output.

4. The induction heating cooker according to claim 1 or 2,

the 1 st prescribed increase amount is variable.

5. The induction heating cooker according to claim 4,

the induction heating cooker further includes:

an input current detection unit that detects the magnitude of an input current supplied from a power supply; and

a heating coil current detection unit that detects a magnitude of a heating coil current flowing through the heating coil,

the control unit determines a material of the cooking container based on the detected magnitude of the input current and the magnitude of the heating coil current at the start of the warm-up mode, and sets the 1 st predetermined increase amount based on the determined material of the cooking container.

6. The induction heating cooker according to claim 4,

the induction heating cooker further includes:

a buoyancy reducing plate disposed between the top plate and the heating coil; and

a temperature detection unit that detects a temperature of the buoyancy reduction plate,

the control unit sets the 1 st predetermined increase amount based on the temperature of the buoyancy reducing plate from the start of heating with the 1 st heating output detected by the temperature detection unit.

7. The induction heating cooker according to claim 4,

the induction heating cooker further includes:

a buoyancy reducing plate disposed between the top plate and the heating coil;

a 1 st temperature detector that detects a temperature of the buoyancy reducing plate; and

a 2 nd temperature detecting unit for detecting a temperature of the top plate,

the control unit determines whether or not the bottom surface of the cooking container is warped based on a difference between the temperature detected by the 1 st temperature detecting unit and the temperature detected by the 2 nd temperature detecting unit, and sets the 1 st predetermined increment based on whether or not the bottom surface of the cooking container is warped.

8. The induction heating cooker according to claim 1 or 2,

the control unit includes an input power integrating unit for integrating input power,

when the increase amount of the output value of the infrared sensor from the start of heating at the 1 st heating output does not exceed the 1 st predetermined increase amount, the notification unit is caused to notify that the warm-up is completed and transition is made to the standby mode when the integrated value of the input power integrated by the input power integration unit from the start of heating at the 1 st heating output exceeds a predetermined power integrated value.

9. The induction heating cooker according to claim 8,

the predetermined power integration value is variable.

10. The induction heating cooker according to claim 9,

the induction heating cooker further includes:

an input current detection unit that detects the magnitude of an input current supplied from a power supply; and

a heating coil current detection unit that detects a magnitude of a heating coil current flowing through the heating coil,

the control unit determines a material of the cooking container based on the detected magnitude of the input current and the magnitude of the heating coil current at the start of the warm-up mode, and sets the predetermined integrated power value based on the determined material of the cooking container.

11. The induction heating cooker according to claim 3,

the operation unit further includes a heating power setting unit for causing a user to instruct a heating power setting of the inverter circuit,

in the standby mode, when the user inputs an instruction to change the heating power setting through the heating power setting unit, the heating mode is switched to a heating mode in which heating is performed with a 4 th heating output corresponding to the instructed heating power,

in the heating mode of the said air conditioner,

heating or stopping heating with a 5 th heating output smaller than the 4 th heating output when the increase of the output value of the infrared sensor exceeds a 4 th prescribed increase,

and heating with the 4 th heating output when an increase in the output value of the infrared sensor is smaller than a 5 th predetermined increase that is equal to or smaller than the 4 th predetermined increase.

12. The induction heating cooker according to claim 11,

when the 4 th heating output is larger than the 2 nd heating output, the 4 th predetermined increase amount is made larger than the 2 nd predetermined increase amount.

13. The induction heating cooker according to claim 11,

when the 4 th heating output is smaller than the 2 nd heating output, the 4 th predetermined increase amount is made equal to the 1 st predetermined increase amount.

14. The induction heating cooker according to claim 1 or 2,

the infrared sensor is provided in the middle of the winding of the heating coil in the radial direction.

15. The induction heating cooker according to claim 1 or 2,

the infrared sensor includes a silicon photodiode.