JPH0719653B2 - Boiling detector - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiling detection device that heats water contained in a pot or the like and detects boiling of the water.

2. Description of the Related Art Conventional boiling detection devices are applied to sheathed heater stoves, gas stoves, and the like. . FIG. 5 shows the configuration of the sheathed heater stove. In the figure, reference numeral 1 denotes a spiral sheathed heater attached to the main body 2, on which the pot 3 is directly placed for use. Reference numeral 4 denotes a temperature detecting device for detecting the temperature of the pot 3, which is attached to the bottom of the pot 3 by pressure contact with a spring or the like. In the case of the above configuration, the output of the temperature detection device 4 shows a clear bending point (boiling point) as shown in A of FIG. However, in the case of an induction heating cooker or the like in which the temperature detecting device 4 is attached via the top plate 5 as shown in FIG. 6, a curve without a bending point is formed as shown in FIG. 7B. I will draw. That is, pot 3
This is because the temperature detecting device 4 is arranged via the top plate 5 on which the pot is placed, and therefore the temperature of the pot is not directly detected. Further, when the thermal coupling between the container and the temperature detector is poor, a curve having no bending point and having a small rate of change is drawn as shown in C of FIG.

Problems to be Solved by the Invention However, in the configuration of the conventional induction heating cooker or the like, since there is no bending point in the temperature curve, even if a slight error in reading the temperature change, the boiling point is significantly different from the accuracy. Had a problem.

In view of the above problems, it is an object of the present invention to perform boiling detection with high accuracy even when the temperature change is slightly read.

Means for Solving the Problems In order to achieve the above object, the present invention provides a temperature detecting means thermally coupled to a container containing water heated by a heating source and a temperature signal from the temperature detecting means. Based on the temperature change detecting means for calculating the temperature change rate based on the temperature change signal and the temperature change signal from the temperature change detecting means a predetermined time after the start of heating, the set temperature is determined based on the temperature change rate. Temperature determining means, a timer means for counting the integrated time from the start of heating when the temperature signal from the temperature detecting means and the set temperature are the same, and the integrated time from the timer means are input. The configuration is provided with a time determining means for determining the time until the completion of boiling based on the integrated time.

Action According to the above configuration, the rate of temperature change is detected after a predetermined time has elapsed since the start of heating. That is, when the thermal coupling between the temperature detecting means and the container is poor, the set temperature also becomes low, and if the temperature change rate is detected, the set temperature can be correctly determined even if the thermal coupling changes. Furthermore, the time from the start of heating until the temperature reaches the set temperature is measured, and the time until the completion of boiling is determined according to the value, so that the error in detecting the temperature change rate can be corrected. That is, when the temperature change rate is detected high, the time to completion of boiling is short, and when it is detected low, on the contrary, the time to completion of boiling is determined to be long, thereby reducing the error at the boiling point and increasing the accuracy. You can

Example Hereinafter, the configuration of the boiling detection apparatus in one example of the present invention will be described with reference to FIG. In the figure, 11 is a container for containing water 12, and this container 11 is thermally coupled to the temperature detecting means 13. Using the temperature detected by the temperature detecting means 13 as an input signal, a temperature change detecting means 14 for calculating a temperature change rate,
Using the temperature change rate of the temperature change detection means 14 as an input signal, the temperature determination means 15 for determining the temperature from the temperature detection means 13 at the set temperature, the set temperature of the temperature determination means 15, and the temperature of the temperature detection means 13 When the timer means 16 that counts the cumulative time from the start of heating when the two match, and the cumulative time counted by the timer means 16 as an input signal,
Time determination means for determining the time to stop the operation of the heating source 21
17 and a control means 18 that controls the heating source driving means 20 to stop the operation of the heating source 21 that heats the container 11
14 to 18 are composed of a microcomputer 19 including a CPU, ROM, RAM and input / output ports.

FIG. 2 shows an example in which the boiling detection device having the above configuration is used in an induction heating cooker. In FIG. 2, reference numeral 22 is an AC power supply, which is connected to a rectifier circuit 24 via a power switch 23. On the DC side of this rectifier circuit 24, a container for containing the water 12
It is attached to the back of the top plate 25 on which 11 is placed,
A series connection of a temperature thermistor 26 and a resistor 27, which are thermally coupled to the container 11, is connected, and the voltage (temperature signal) at the connection point a is
The microcomputer 19 is input as a digital signal via the A / D converter 28. A heating coil 29 for inductively heating the container 11, a resonance capacitor 30, and a switching element 31 are connected to the DC side of the rectifier circuit 24. The switching element 31 is turned on and off by the driving transistor 32 and causes a high frequency current to flow through the heating coil 29.

Next, the operation of the microcomputer 19 will be described with reference to FIG. First, in step 41, the driving transistor 32 is operated, the switching element 31 is turned on and off, and a high frequency current is passed through the heating coil 29. If it is determined in step 42 that the predetermined time has elapsed, the temperature detection signal from the thermistor 26 is input in step 43, and the temperature change rate is calculated in step 44. Then, in step 45, the set temperature is determined based on this temperature change rate. The determination of the set temperature will be described in detail with reference to FIG. Temperature change rate [Delta] T at a given time t ₀ has elapsed time point, within a reading error, the value of _{ΔT 1 ~ΔT 3 (ΔT 1 <} ΔT 2 <ΔT 3). Here, if the temperature change rate [Delta] T was read and [Delta] T _1, the set temperature based on the temperature change rate [Delta] T ₁ is determined to T _1. Similarly, in the case of ΔT ₂ and ΔT ₃ , T ₂ and T ₃ are determined. That is, the temperature change rate ΔT
When is small, the set temperature is determined to be low. The temperature thus determined is compared with the temperature determined by the temperature thermistor 26.
If it is judged that the temperature of 26 has reached the set temperature, step 47
The total time t from the start of heating is calculated with. Then step 48
Then, the time to stop is determined based on the time accumulated in step 47. The determination of the time until the stop will be described in detail with reference to FIG. Integrated time determines the time until the boiling t _B and t ₁ to t _1-B. Similarly for t ₂ and t ₃ , t _2−B and t
_3-B is decided. That is, when the integration time is short, the time to stop is set to be long. If it is determined in step 49 that the time until the stop thus determined has passed, in step 50, the boiling is completed, and the step is completed.
At 51, the driving transistor 32 is turned off, and the energization of the heating coil 29 is stopped.

EFFECTS OF THE INVENTION As is clear from the above examples, according to the present invention, even if the thermal coupling between the temperature detecting means and the container changes, the change in the coupling is determined by the temperature change rate and the change rate is determined. Since the set temperature is also changed accordingly, an error caused by a change in thermal coupling can be reduced. Further, since the set temperature is set lower than the boiling point, the reading error can be reduced. Further, even if there is an error in the rate of temperature change, the time until the boiling is completed is determined again based on the time to the set temperature, so the error can be corrected at that point, and boiling can be detected with high accuracy at all times. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a boiling detection device according to an embodiment of the present invention, FIG. 2 is a circuit configuration diagram of an induction heating cooker using the device, and FIG. 3 is a microcomputer thereof. FIG. 4 is a control characteristic diagram of the present invention, FIG. 5 is a side sectional view of a sheath heater, FIG. 6 is a side sectional view of an induction heating cooker, and FIG. 7 is detection of a temperature detecting element. It is a characteristic view which shows the temperature change. 11 ... container, 13 ... temperature detecting means, 14 ... temperature change detecting means, 15 ... temperature determining means, 16 ... timer means, 17 ...
… Time determination means.

Claims (1)

[Claims] 1. A temperature detecting means thermally coupled to a container containing water heated by a heating source and a temperature change detecting means for calculating a temperature change rate based on a temperature signal from the temperature detecting means. After a predetermined time from the start of heating, the temperature change signal from the temperature change detection means is input, and based on this temperature change rate, the temperature determination means for determining the set temperature, and the temperature signal from the temperature detection means. A timer means for counting an integrated time from the start of heating when the set temperature is the same, and an integrated time from the timer means are inputted, and a time determination for determining a time until completion of boiling based on the integrated time Boiling detector equipped with means.