JP2000156281A - Induction heating cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem of coarse power adjustment because of change of power change quantity per increase/decrease width of on-time of a switching element in heating loads of different forms and materials. SOLUTION: This induction heating cooker is provided with a resonance circuit 3 composed of a heating coil 1 and a capacitor 2, an inverter circuit 5 composed of at least one switching element 4 connected to the resonance circuit 3 serially or in parallel, a power source 6 to supply power to the inverter circuit 5, a power detection means 7 to detect power to be supplied to the inverter circuit 5, a control means to control input power in plural stages by outputting on-time of the switching element 4, and a power change quantity detection means 9 to detect power change quantity per stage, and the control means changes increase/decrease width of on-time in accordance with the power change quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating cooker used in general households and restaurants, and more particularly, it has a feature in the control means of the induction heating inverter circuit.

[0002]

2. Description of the Related Art In a conventional induction heating cooker, a plurality of output terminals from a microcomputer (hereinafter, referred to as a microcomputer) serving as a control means is used to set a set power in a range of increase or decrease of a conduction time of a predetermined switching element. Power was being adjusted.

[0003] Fig. 14 is a circuit diagram of a conventional inverter for induction heating, and Fig. 15 shows a power change characteristic when power is adjusted to set power using the conventional control means. The conventional control means will be described.

FIG. 14 shows an example of a circuit of an induction heating cooker. In FIG. 14, reference numeral 21 denotes a heating coil, on which an object to be heated (a pan or the like) is placed, though not particularly shown in the figure, and 22, a condenser connected in parallel with the heating coil 21 to form a resonance circuit 23. I do. Reference numeral 24 denotes a switching element having a built-in reverse conducting diode, which is connected in series with the resonance circuit 23 to form an inverter circuit 25.

A power supply 26 supplies power to the inverter circuit 25, and a power detecting means 27 detects power supplied to the inverter circuit 25.

Reference numeral 28 denotes a microcomputer, which performs power detection via a power detection means 27, and a driving circuit 30 includes an oscillation circuit 31.
The switching element 24 is turned on and off so as to reach the set power in accordance with the output pulse signal formed by the output terminal of the microcomputer 28.

FIG. 15 shows the power change characteristics of the conventional control means. When pots of different materials are heated, the conduction time of the switching element 24 is greatly different even if the power supplied to the inverter circuit is equal. Is shown.

[0008]

However, in the above-mentioned conventional inverter circuit control means, the conduction time of the switching element at the maximum set power of the design standard pan is divided by the number of divisions determined by the number of output terminals of the microcomputer. Since the power was adjusted by increasing or decreasing the conduction time, the shape and
When a load made of different materials is heated, there has been a problem that the amount of power change per increment / decrement width changes and the power adjustment becomes coarse.

FIG. 15 shows the power change characteristics of pots of different materials. The characteristics of a design standard pot are the characteristics of a magnetic pot, and the characteristics of a non-magnetic pot are different from those of a different material.

In FIG. 15, Px is the maximum set power of the design standard pan, the conduction time of the switching element at that time is Tx, the number of divisions determined by the number of output terminals of the microcomputer is n, and the maximum set power Px is the number of divisions. The power change amount divided by n is dpx, and the increase / decrease width obtained by dividing the conduction time Tx by the number of divisions n is d.
tx. In addition, when heating different pot materials, the power change amount per increase / decrease width dtx is defined as dpy.

The amount of power change dpx and dpy per increase / decrease width dtx greatly differs depending on the material of the pot, as clearly shown in FIG.
When x becomes large like dpy, there is a problem that the power change amount per one step is too large to adjust to the set power, and the adjustment becomes coarse, which affects the cooking performance.

In FIG. 15, when the power is small and the power is large in the same design standard pan, the power change amount is different. When the set power is small, that is, when the pan is induction-heated with a small heating power, If dpx is large, there is a problem that the power adjustment is substantially coarsened and the cooking performance is affected.

In order to solve these problems by using the conventional control means, it is necessary to increase the number of divisions by adding the number of output terminals of the microcomputer. Challenges had arisen.

[0014]

According to one aspect of the present invention, there is provided a control unit for outputting a conduction time of a switching element, wherein the control means outputs a conduction time of the switching element in accordance with an amount of power change. To adjust the power.

Further, the power is adjusted so as to increase or decrease the amount of power change until the set power is reached, so as to reach the set power.

[0016] Further, the width of increase or decrease of the conduction time is adjusted so as to adjust the power with a power change amount determined for each set power.

Further, the power is adjusted so as to reach the set temperature by adjusting the amount of power change until the set temperature is reached.

Further, power adjustment is performed according to the increase / decrease range in which the maximum value is set. Further, the output is controlled in accordance with the amount of power change with respect to the increase / decrease width of the conduction time per stage.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, there is provided a resonance circuit including a heating coil and a capacitor, and at least one switching element connected in series or parallel with the resonance circuit. And a power supply for supplying power to the inverter circuit, power detection means for detecting power supplied to the inverter circuit, and outputting the conduction time of the switching element to output power in a plurality of stages. Control means for controlling and power change amount detecting means for detecting a power change amount per one stage are provided, and the control means varies an increase / decrease width of the conduction time according to the power change amount.

[0020] With this configuration, even when a load having a different material and shape is induction-heated, it is possible to maintain the same power adjustment performance as that of the design standard pan.

The present invention according to claim 2 of the present invention comprises a power setting means for changing the amount of power change by adjusting the width of increase or decrease of the conduction time until the set power is reached. Regardless of the shape load, rapid power adjustment and adjustment performance are ensured.

According to a third aspect of the present invention, there is provided a configuration in which the width of increase or decrease of the conduction time is adjusted so as to adjust the power with a power variation determined for each set power. -Fine power adjustment performance can be achieved irrespective of the shape load.

According to a fourth aspect of the present invention, different materials are provided by providing a temperature setting means and a temperature detecting means, wherein the power change amount is changed by increasing or decreasing the width of increase or decrease in the conduction time until the temperature reaches the set temperature. -Rapid temperature adjustment and adjustment performance are ensured regardless of the shape load.

According to a fifth aspect of the present invention, by providing the maximum value of the increase / decrease range, a load which is not suitable for induction heating, such as a spoon or a fork, having a small power variation is placed on the induction heating cooker. In such a case, it is possible to prevent a situation in which the conduction time of the switching element becomes excessive due to an increase in the increase / decrease width, thereby heating an inappropriate load.

According to a sixth aspect of the present invention, the output of the control means is controlled in accordance with the amount of power change with respect to the amount of increase or decrease in the conduction time. A situation in which a load inappropriate for induction heating is heated can be prevented.

[0026]

(Embodiment 1) FIG. 1 shows a circuit configuration according to a first aspect of the present invention. In FIG. 1, a resonance circuit 3 including a heating coil 1 and a capacitor 2, an inverter circuit 5 including a switching element 4 connected in series with the resonance circuit 3, and a power supply 6 for supplying power to the inverter circuit 5
A power detection means 7 for detecting power supplied to the inverter circuit 5, a microcomputer 8 for outputting the conduction time of the switching element 4 to control the power in n stages, and detecting an amount of power change per stage Power change amount detection means 9;
The microcomputer 8 varies the width of increase or decrease in the conduction time according to the amount of power change detected by the power change amount detecting means 9. The microcomputer 8 outputs the conduction time to the drive circuit 10, and the switching element 4 is on / off controlled.

In this embodiment, the resonance circuit 3 is formed by connecting the heating coil 1 and the capacitor 2 in parallel. However, as shown in the circuit configuration example of FIG. 2, the resonance circuit 3 is formed by series connection. It is also possible to do.

Similarly, in this embodiment, the resonance circuit 3
Although the inverter circuit 5 is configured by series connection of the switching element 4 and the switching element 4, as shown in FIG. 2, the inverter circuit 5 can be configured by parallel connection.

In addition, FIGS. 3 and 4 show examples of circuit configurations using two switching elements.

FIG. 3 shows the circuit configuration of FIG.
1 and a switching element 12, and a heating coil 1
And the capacitor 2 constitute a resonance circuit 3 by parallel connection,
The power input to the inverter circuit 5 is controlled by the conduction time of the switching element 4 and the switching element 12.

FIG. 4 includes the circuit configuration of FIG. 2 and a switching element 12. The heating coil 1 and the capacitor 2 form a resonance circuit 3 by series connection, and the switching element 4 and the switching element 12 Are connected in parallel and in series, respectively, and control the power input to the inverter circuit 5 by the conduction time of the switching element 4 and the switching element 12.

Further, a configuration is described in which the voltage and current input to the inverter circuit 5 are detected as power detection means. However, when there is almost no change in the voltage of the power supply 6, the current and power are in a proportional relationship. Therefore, it is possible to control the current detection unit as a power detection unit. Further, the power supply 6 is equivalent to a power supply configuration in which a commercial power supply is rectified by a rectifier, and a similar function can be obtained by inserting the power detection means 7 between the commercial power supply and the rectifier to perform detection.

Further, since the voltage across the switching element is proportional to the current output from the power supply 6 when a predetermined load is used, the means for detecting the voltage across the switching element is regarded as the power detecting means. A controlled control is also possible.

FIG. 5 shows an example of the characteristics of the conduction time and the power of the switching element using the control means of the present invention. In FIG. 5, when heating the design standard pan, the increase / decrease width of the conduction time is adjusted as dtx1, and when heating a pan of a different material, the increase / decrease width of the conduction time is adjusted as dty1, so that the amount of power change is equal. FIG.

(Embodiment 2) FIG. 6 shows a circuit configuration according to a second aspect of the present invention. FIG. 6 shows a circuit configuration including the circuit configuration of FIG. 1 and 13 power setting units.

FIG. 7 shows an example of the characteristics of the conduction time and the power of the switching element using the control means of the present invention. In FIG. 7, the power adjustment set by the power setting means 13 is dt until the vicinity of the set power.
x3, in the vicinity of the set power, the power is adjusted by increasing or decreasing the conduction time of dtx1, and by setting dtx3 to be larger than dtx1, rapid power adjustment is performed, and fine power adjustment is performed on the set power. It is possible to do.

In this embodiment, the power is adjusted by the two types of increase / decrease of the conduction time dtx1 and dtx3. However, when the power is adjusted by the n types of increase / decrease, the increase / decrease per stage is further increased. It can be set large,
Needless to say, there is an advantage that the power can be adjusted more rapidly.

In addition, even if the pots have different materials and shapes, when the power is adjusted by the control means of the present invention, the width of increase or decrease of the conduction time is adjusted so as to adjust the power with the same amount of power change.
It is needless to say that the same power adjustment performance is ensured since the x3 is adjusted as dty3 and the dtx1 is adjusted as dty1.

(Embodiment 3) FIG. 8 shows an example of the conduction time and power characteristics of a switching element using the control means of the present invention. In FIG. 8, dtx1 indicates an increase / decrease width of the conduction time when the power setting means 13 sets the maximum power Px, and dtx2 indicates a fluctuation time of the conduction time when the power setting means 13 sets the minimum power Pm. dt
By setting the power change amount dpx1 due to x2 to be smaller than the power change amount dpx2 due to dtx1, fine power adjustment based on the power change amount according to the set power becomes possible.

In addition, the control means of the present invention also adjusts the range of increase and decrease of the conduction time with respect to dtx2 so that the control means of the present invention adjusts the power with the same power change amounts dpx1 and dpx2 even for pans having different materials and shapes. Dty2, dtx
It is needless to say that the same power adjustment performance is ensured because the power adjustment is made to be equal to or equal to 1 in dty1.

(Embodiment 4) FIG. 9 shows a circuit configuration according to a fourth aspect of the present invention. FIG. 9 shows a circuit configuration including the circuit configuration of FIG. 1, 14 temperature setting units, and 15 temperature detection units. Here, the temperature detecting means 14 detects the temperature of a load such as a pot to be induction-heated.

FIG. 10 shows an example of the conduction time and power characteristics of the switching element for controlling the present invention.
In FIG. 10, the temperature is increased or decreased by dpx4 in order to rapidly raise the temperature up to the vicinity of the temperature set by the temperature setting means 14, and the power is changed by dpx5 in the vicinity of the set temperature in order to perform fine temperature adjustment. Make adjustments. Power change amount dpx4, dpx in design standard pan
5 are dtx4, dtx5,
Power change amount dpx4, dpx5 in pots of different materials
The amount of increase or decrease of the conduction time for realizing is dty4 and dty5, and it is possible to control a pot of a different material with the same power change amount as the design standard pot.

FIG. 11 shows the change over time of the load temperature when the control means of the present invention is used. For comparison, the dotted line shows the change over time of the load temperature by the conventional control means.

Conventionally, when heating pots of different materials,
Since the increase / decrease range is constant, the amount of change in electric power is larger than that in the design standard pan, and a large overshoot has occurred with respect to the set temperature T1. However, as shown in FIG. 10, the amount of power change per increase / decrease range can be controlled to a set value regardless of different materials / shapes. Becomes possible.

In this embodiment, the temperature is adjusted by the two types of increase / decrease of the conduction time dtx1 and dtx3. However, if the temperature is adjusted by the n types of increase / decrease, the increase / decrease per stage is further increased. It can be set large,
There is an advantage that steep temperature adjustment is possible.

(Embodiment 5) FIG. 12 shows characteristics of the conduction time and power of a switching element using the control means of the present invention. In the control for varying the increase / decrease width of the conduction time in order to obtain a predetermined power increase amount, when a load inappropriate for heating such as a spoon or a knife is placed on the induction heating cooker, the conduction time is reduced. Change width dty
5 is excessive. As a result, when the predetermined power Py is not obtained in the predetermined conduction time Ty, even if it is determined that the load is a load for stopping the heating at the load determination point where the load is determined to be inappropriate for the heating, an excessive load is determined. Heating of an improper load is performed depending on the increase / decrease width of the conduction time. By providing the maximum value of the increase / decrease width of the conduction time in order to prevent this phenomenon, control that does not perform heating for a load inappropriate for induction heating is realized.

(Embodiment 6) FIG. 13 shows the characteristics of the increase width of the conduction time of the switching element and the power change rate using the control means of the present invention. In the control for varying the increase / decrease width of the conduction time to obtain a predetermined power increase amount, if the power change amount for the increase / decrease width of the conduction time is equal to or less than a predetermined value, an improper load for the induction heating is placed. And stop the conduction of the switching element. As a result, control without performing transient heating is realized.

[0048]

As is apparent from the above embodiment, the invention according to the first aspect adjusts the width of increase or decrease of the conduction time according to the amount of power change in the conduction time of the switching element output by the control means. By doing so, even when a load having a different material and shape is induction-heated, the effect of maintaining the same power adjustment performance as that of the design standard pan can be obtained.

According to the second aspect of the present invention, the width of increase or decrease of the conduction time is adjusted until the set power is reached,
For example, it is possible to improve the adjustment speed while maintaining the performance of fine power adjustment by adjusting the power with a large power change amount near the set power and adjusting with a small power change amount near the set power. The effect is obtained.

According to the invention of claim 3 of the present invention, the power change amount is set, for example, when the set power is small, the power change amount is small, and when the set power is large, the power change amount is set. With a large configuration, it is possible to obtain an effect that the power adjustment performance at each set power can be ensured regardless of different pot materials.

According to the invention described in claim 4 of the present invention, the adjustment is performed by a large amount of power change until the temperature reaches the set temperature, for example, near the set temperature, and is adjusted by the same small amount of power change near the set temperature. Has the effect that the temperature adjustment performance can be maintained and the adjustment speed can be improved irrespective of different pot materials.

According to a fifth aspect of the present invention, there is provided an induction heating cooker in which electric power is adjusted by changing the increase / decrease width of the conduction time, and by setting a maximum value of the increase / decrease width, for example, a spoon having a small power change amount. For a load inappropriate for induction heating, such as a fork or a fork, the effect of increasing or decreasing the amount of increase or decrease can be obtained.

According to a seventh aspect of the present invention, in the control for varying the increase / decrease width of the conduction time, the amount of power change with respect to the increase / decrease width of the conduction time is detected, and if it is less than a predetermined value, conduction is stopped. . As a result, an effect is obtained that heating is not performed for a load that is inappropriate for induction heating.

It is easy to guess that the effects of the first to seventh aspects can be obtained synergistically even when combined. For example, by combining the inventions of claim 2 and claim 3 and providing two types of increase / decrease ranges for each set power,
The effect of rapid and fine power adjustment can be obtained at each set power, and for example, by combining the inventions of claim 1, claim 2, and claim 3, with respect to loads of different materials and shapes, The effect of rapid and fine power adjustment in each power setting can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention;

FIG. 2 is a diagram showing a different circuit configuration according to the first embodiment of the present invention;

FIG. 3 is a circuit configuration diagram including two switching elements according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a different circuit configuration having two switching elements according to the first embodiment of the present invention;

FIG. 5 is a diagram showing the relationship between the conduction time and the power characteristics of the switching element according to the first embodiment of the present invention.

FIG. 6 is a circuit configuration diagram according to the second and third embodiments of the present invention.

FIG. 7 is a diagram showing a relationship between a conduction time and a power characteristic of a switching element according to a second embodiment of the present invention.

FIG. 8 is a diagram showing the relationship between the conduction time and the power characteristics of the switching element according to the third embodiment of the present invention.

FIG. 9 is a circuit configuration diagram according to a fourth embodiment of the present invention.

FIG. 10 is a diagram showing a relationship between a conduction time and a power characteristic of a switching element according to a fourth embodiment of the present invention.

FIG. 11 is a diagram showing a heating time and a load temperature characteristic according to the fourth embodiment of the present invention.

FIG. 12 is a diagram showing a relationship between a conduction time and a power characteristic of a switching element according to a fifth embodiment of the present invention.

FIG. 13 is a diagram showing the relationship between the conduction time and the power characteristics of the switching element according to the sixth embodiment of the present invention.

FIG. 14 is a configuration diagram of a circuit using control means of a conventional example.

FIG. 15 is a diagram showing a relationship between a conduction time and a power characteristic of a conventional switching element.

[Explanation of symbols]

 1,21 Heating coil 2,11,22 Capacitor 3,23 Resonant circuit 4,12,24 Switching element 5,25 Inverter circuit 6,26 Power supply 7,27 Power detection means 8,28 Microcomputer 9 Power change detection means 10 Drive Circuit 13 Power setting means 14 Temperature setting means 15 Temperature detection means

Claims (6)

[Claims] 1. A resonance circuit including a heating coil and a capacitor, an inverter circuit including at least one or more switching elements connected in series or in parallel with the resonance circuit, and supplying power to the inverter circuit. Power supply, power detection means for detecting power supplied to the inverter circuit, and control means for outputting the conduction time of the switching element and controlling power in a plurality of stages;
A power change amount detecting means for detecting a power change amount per one stage, wherein an output of the control means varies a width of increase or decrease of a conduction time of the switching element in accordance with the power change amount per one stage to perform power adjustment. Do induction heating cooker. 2. A control device having power setting means for outputting a conduction time of a switching element, wherein the control means adjusts an increase / decrease range of the conduction time until the set power is reached, and adjusts the power so as to reach the set power. The induction heating cooker according to claim 1, wherein the induction heating cooker is performed. 3. The induction heating cooker according to claim 2, wherein the control means adjusts the power according to a power change amount set for each set power. 4. It has a temperature setting means and a temperature detection circuit,
2. The induction heating cooker according to claim 1, wherein the control means for outputting the conduction time of the switching element adjusts the temperature by increasing or decreasing the conduction time until the temperature reaches the set temperature. 5. The induction heating cooker according to claim 1, wherein the control means adjusts the power in accordance with the increase / decrease range in which the maximum value is set. 6. The control means according to claim 1, wherein the control means controls an output in accordance with a power change amount with respect to an increase / decrease width per one stage.
5. The induction heating cooker according to any one of 5.