JPH0258532B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to cooking with a high moisture content, such as stewing, using a heating cooker such as a stove.
The present invention relates to a cooking temperature control device that can control the temperature of food to be cooked at a constant level with high precision.

BACKGROUND TECHNOLOGY Traditionally, stews and other stews require heating with strong heat at the beginning, and then boiling the contents over low heat for a long time once the contents have boiled. Up until now, these operations had been performed by humans, so there were many mistakes such as forgetting to turn down the heat even when the food was boiling, resulting in burnt food. Moreover, in this case, energy is wasted. Therefore, an automatic control device that detects the temperature of the contents and automatically reduces the heat when the contents boil is being considered. However, inserting a temperature sensor into a cooking pot to detect the temperature of the contents is inconvenient and unsanitary. For this reason, a method has been developed in which a temperature sensor is brought into contact with the bottom of a cooking pot to detect the bottom temperature of the pot and to infer the temperature of the contents.

Problems to be Solved by the Invention However, this method has a drawback in that the temperature at the bottom of the pot and the temperature of the contents are not constant and vary depending on the material shape, thickness, amount of contents, etc. of the pot.

For example, as a conventional control means, the signal of the sensor 6 is directly introduced into the proportional control section 10 as shown in FIG.
As a result, there was a structure in which a drive signal for the proportional control valve 2 was output. FIG. 5 is a control system diagram of a gas table stove, where 1 is a gas inlet, and gas passes through a proportional control valve 2 and is combusted in a burner 3. The burner 3 heats the bottom of the pot 4 and adds heat to the food 5 to be cooked. Reference numeral 6 denotes a temperature sensor that detects the bottom surface temperature of the pot 4, and this signal is input to the proportional control section 10 to drive the proportional control valve 2 and control the combustion amount of the burner 3.

With the above configuration, the signal from the sensor 6 is transmitted to the proportional control section 10.
When the temperature is lower than the set temperature, the proportional valve 2 is fully opened and the burner 3 is at maximum combustion. As the temperature of the sensor 6 rises and approaches the set temperature, the proportional valve 2 gradually begins to throttle and the amount of combustion is also throttled. When the temperature of the sensor 6 reaches the set temperature, the proportional valve 2 is throttled down to the minimum, and the burner 3 reaches the minimum combustion amount that allows safe combustion.

In this case, there is no problem as long as the correlation between the temperature of the sensor 6 and the temperature of the food 5 is constant. However, it is difficult to correlate the temperature of the sensor 6 and the temperature of the food 5 because the pot and the amount of cooking vary depending on the food being cooked.

Especially in stew dishes, the temperature at which the inside boils, that is, the timing to reduce the heat after boiling, is when the temperature of the contents reaches 100 degrees Celsius if the atmospheric pressure is 1 atm. When the set temperature is set, the temperature of the contents will never reach the set temperature no matter how long it takes (water has a temperature of 100 at 1 atm).
℃), the proportional valve does not work and the firepower is not reduced. On the other hand, if the temperature is too low, the heat will be turned down before the temperature reaches 100°C, and subsequent heating will be done over low heat, so the temperature will not come to a boil easily, so a very precise temperature setting is required.
Furthermore, temperature control becomes impossible when considering the above-mentioned variations depending on the pot and the amount of food to be cooked.

In addition to this, if the boiling point of water changes, it becomes impossible to detect the boiling point using conventional control methods. For example, when cooking using a pressure cooker, the internal pressure increases and the boiling temperature reaches 120-130℃,
It will not boil at ℃. In addition, at high altitudes with low atmospheric pressure, it boils at temperatures below 100°C, and the temperature does not rise to 100°C, causing boiling over and burning. Similar problems arise even in a configuration in which the temperature sensor is inserted directly into the food being cooked.

Means for Solving the Problems In order to solve the above problems, the present invention provides a means for detecting the temperature of the food heated by the heating means, and a heating control means for controlling the amount of heating according to this signal. A temperature control unit that outputs a control signal is provided, and the temperature control unit includes a slope detection unit that detects a slope of temperature rise of the food to be cooked, and the temperature slope becomes equal to or less than a predetermined value when the food boils. A bending point detection section for detecting the bending point is provided, and a storage section stores the output of the temperature detection means when the boiling detection signal from the bending point detection section is generated as a set temperature, and a storage section that stores this value and the temperature detection means from now on. The configuration includes a proportional control section that outputs a signal to the heating control means so as to control the amount of heating of the food according to the temperature difference from the output.

Function The above configuration allows direct detection of changes in atmospheric pressure, sensor variations, or the temperature of the food when cooking food with a large amount of water, such as in simmering or boiling water. Even if the food does not boil, it accurately detects that the food has boiled, stores the sensor temperature at this time, and controls the heating amount to maintain this temperature from then on.

Example The present invention will be explained below with reference to the drawings.

FIG. 1 is a diagram showing an example of a control system to which the present invention is applied. This example shows an application to a gas table stove.

1 is a gas inlet, and gas passes through a proportional control valve 2 and is burned in a burner 3. The burner 3 heats the bottom of the pot 4 and adds heat to the food 5 to be cooked. 6 is a temperature sensor that detects the bottom surface temperature of the pot 4, and this signal is transmitted to the temperature control section 7. The temperature control section 7 includes an inclination detection section 8, a bending point detection section 9, and a proportional control section 1.
0 and drives the proportional control valve 2 to control the combustion amount of the burner 3.

The present invention focuses on the fact that when water boils at 1 atm, the temperature reaches 100°C and does not rise any further, and is configured to detect the slope of temperature rise.

FIG. 2 shows temperature rise characteristics, with the horizontal axis X representing time and the vertical axis T representing temperature. The figure shows an example of the characteristics when boiling water. A shows the temperature of the contents, that is, the water temperature, and B shows the temperature of the bottom of the pot, that is, the temperature detected by the sensor 6. temperature
Ta increases on both curves A and B due to heating at room temperature, and at temperature Tb, the increasing curve once becomes gentle and begins to rise again. This is because the moisture condensed around the container evaporates at temperature Tb.
This temperature varies depending on the material and size of the container (pot), but is approximately 40 to 70°C.

As the temperature further increases, the temperature Tc reaches 100°C, and at one atmospheric pressure, the water temperature A boils and does not rise above 100°C. At this time, the temperature B of the sensor is Td, and since the water temperature A reaches 100° C., the rising characteristic of Td becomes very small or disappears. this
The temperature difference between Tc (100℃) and Td varies greatly depending on the material of the pot and the amount and type of food being cooked. Also, if the pressure changes using a pressure cooker or the like, the temperature Tc itself will no longer be 100°C. However, the inflection point C where the slope of temperature rise changes is always the point where water boils.

FIG. 3 is a diagram showing an example of tilt detection or bending point detection. This method uses sampling time ΔX
The bending point detection unit 9 measures the temperature change ΔT at each
The point where ΔT becomes below a certain value is determined to be the inflection point, and the temperature Td at that time is the content temperature of 100℃.
This is a method to set the temperature to . In addition to this method, the bending point detection section may also detect when the ratio of temperature rise falls below a certain value. In other words, (Tn−Tn−
1) Let Td be the point where /(Tn-1-Tn-2) is below a certain value. (This equation may be in any form as long as it determines the slope ratio.) The proportional control section 10 can shift to various types of control based on the signal from the bending point detection section 9. One possible method is to close the proportional valve 2 based on the signal from the bending point detector 9 to stop combustion. This is ideal for boiling water. Another example is a method of reducing the amount of combustion based on the signal from the bending point detection unit 9 and further heating with a small amount of calories. Generally, stews are cooked using the latter method, and are often simmered over low heat for a long time.

FIG. 4 shows this control characteristic, where the horizontal axis X is time, the vertical axis T of characteristic V is temperature, the broken line A is the temperature of the contents as in FIG. 2, and the solid line B is the temperature characteristic of the sensor at the bottom of the pot. The vertical axis I of the characteristic W indicates the control current of the proportional valve, which is proportional to the combustion amount of the burner 3. Until time Xd, before the signal from the bending point detection section 9 shown in FIG. 3 is output, the proportional valve current is at its maximum, and the combustion amount of the burner 3 is also at its maximum combustion. At time Xd the internal temperature is Tc
(100°C) and starts boiling, the bending point detection unit 9 detects this and sets the proportional valve current to the minimum value, narrowing down the combustion amount to the minimum combustion amount. At this time, the proportional control section 10 has the temperature Td set as the set temperature, and proportionally controls the proportional valve current, that is, the combustion amount, according to the difference between the set temperature and the sensor temperature. Now, if food is added at time Xe, the internal temperature A will decrease. Along with this, the temperature B of the sensor also decreases, and a decrease in the internal temperature A is detected. The proportional control unit 10 increases the proportional valve current to e according to the difference between the temperature Te and the set temperature Td. As a result, the amount of combustion increases and the temperature A
returns to the original temperature Tc, and the amount of combustion also returns to the minimum amount of combustion. The size of Ie above changes depending on the size of Td−Te, and when Td−Te is large, Ie increases and Td−
If Te is small, Ie will be small. The proportional control valve 2 may be an on-off valve or a multistage valve. At this time, the proportional control section 10 is configured to perform on/off control or multi-stage control operation.

Furthermore, as explained in FIG. 2, the bending point detection section 9 is configured to operate from the measurement start temperature Tf or higher so that the bending point detection section 9 does not detect bending due to the temperature Td, thereby eliminating errors in detecting the bending point.

Recently, microcomputers (hereinafter referred to as microcomputers) are often used to create complex control systems such as those described above. FIG. 6 shows a simple flow diagram when the control system described in FIGS. 1 to 4 is created using a microcomputer.

In Fig. 6, IG is a subroutine for the ignition sequence of burner 3, S1 is a subroutine for reading the temperature S1 of sensor 6, and S2 is a subroutine for reading the temperature S1 of sensor 6, and S2 determines the throttle amount of proportional valve 2 according to the size of temperature difference Td - S1 and controls current I. Indicates the subroutine to output.

After ignition, until the sensor temperature S1 reaches the temperature Tf, which is set higher than the unstable temperature Tb part explained in Fig. 2, the process goes through the loop shown in the figure.
Wait for it to become Tf.

Start partial tilt detection when S1>Tf. Here, the temperature S1 of the sensor 6 measured as explained in FIG. 3 is stored for each sampling time ΔX. In other words, when measuring the temperature S1 of sensor 6,
Erase the memory of the sampling temperature two times before and re-memorize the temperature at the first sampling as the temperature two times before (Tn−2←Tn−
1) Restore the value measured during the previous sampling as the previous temperature. (Tn−1←Tn) Furthermore, the temperature S1 measured this time is stored as the current value Tn. (Tn←S1) In this way, the configuration is such that the values in each memory are replaced at every sampling time.

is the calculation section of the bending point detection section, and Tp in the figure is a value determined by the following equation.

Tp=(Tn−Tn−1)/(Tn−1−Tn−2)
In other words, Tp calculates the ratio between the difference between the current measurement value and the measurement value one time ago, and the difference between the measurement value one time ago and the measurement value two times ago. The inflection point is detected when the value of Tp becomes smaller than a predetermined value P, that is, when the increase in each sampling temperature becomes smaller.

If the condition Tp<P is not satisfied, the next sampling time ΔT is measured and stored again in a loop.

After Tp<P and the bending point is detected, the process shifts to the loop shown in the figure and becomes proportional control. Here, the minimum throttle amount Id of the proportional control valve is set in three stages according to the temperature difference before detecting the bending point, that is, the difference between the first temperature and the second temperature (Tn-1-Tn-2). It is configured to switch to (See Figure 4 W) This means that if the slope is large, the amount of cooking is small, so the minimum combustion amount is also reduced (ld''), which reduces the chance of burning of the food, and if the slope is small, the amount of cooking is large. Judging,
The purpose is to increase the minimum combustion amount (ld') and prevent the engine from cooling down. Further, in the proportional control section, the temperature Tn-1 of the sensor just before the bending point detection is performed is stored in the temperature storage section as the set temperature Td, as shown in FIG. The throttle amount of the proportional valve 2 is determined by subroutine S2 so that the difference Td-S1 becomes zero, and the proportional control valve is driven. In other words, if the temperature difference Td-S1 is large, the amount of combustion of the burner is increased because the food is cooling down, and when Td-S1 becomes zero or a negative value, it is assumed that the food is sufficiently boiled. , operates to set the minimum aperture amount Id.

XEND indicates a program that stops combustion of the burner when a preset cooking time X ends.

Although the embodiment of the present invention has been described using a gas stove, similar effects can be obtained with other heaters such as an electric stove. Furthermore, it can be widely applied to cooking appliances such as kettles and rice cookers.

Effects of the Invention As explained above, the cooking temperature control device of the present invention has the following effects.

(1) The structure measures the slope of the temperature rise of the food during simmering and detects the bending point to detect when the temperature of the food has reached the boiling point. Even when the temperature relationship is not constant, that is, due to variations in the sensor or when the temperature at the bottom of the pot is detected as in the example, the boiling point can be accurately detected even when the thickness or material of the pot changes, and the set temperature is low. Detection before boiling,
Even if the set temperature is high and it's boiling, it won't be detected forever, so you don't have to worry about it boiling over or burning, and it's very easy to use and won't cause cooking failures.

(2) The sensor temperature at the bending point is stored as the set temperature, and the proportional control unit compares this temperature with the current sensor temperature and outputs a control signal to the heating control unit. It can automatically switch to low heat and simmer while maintaining the temperature, and if the temperature drops due to addition of ingredients, the amount of combustion is automatically increased and the original temperature is restored in a short time. Therefore, you can safely simmer and cook without any failures such as burning or boiling over, and you can save energy by preventing unnecessary heating.

(3) Similarly, even if the pressure of the food being cooked changes using a pressure cooker or the like, and the boiling temperature reaches a value other than 100°C, the boiling point can be detected accurately, making it applicable to a wide range of cooking applications.

[Brief explanation of drawings]

Fig. 1 is a control system diagram of a cooking temperature control device showing one embodiment of the present invention, Fig. 2 is a characteristic diagram showing the sensor section of Fig. 1 and the rising state of internal temperature, and Fig. 3
The figure is a characteristic diagram explaining the state of inclination detection and bending point detection, Figure 4 is a characteristic diagram explaining the operation of the proportional control section after detecting the bending point, and Figure 5 is a conventional example of a proportional control system using pan bottom temperature detection. Control system diagram, No. 6
The figure is a schematic flow diagram showing an example of a case where the temperature control section (section 7 in FIG. 1) of the present invention is configured with a microcomputer. 2... Proportional control valve (heating control means), 3... Burner (heating means), 4... Pot (container), 5... Food to be cooked, 6... Sensor (temperature detection means), 7... Temperature control Part, 8...Inclination detection part, 9...Bending point detection part, 10...Proportional control part, Td...Set temperature, Tf
...Measurement start temperature, P...predetermined value,
ΔT...Sampling time,...Calculation section,...
...Temperature memory section.

Claims (1)

[Claims] Outputting a control signal to a means for heating a food containing moisture, a temperature detection means for detecting the temperature of the food, and a heating control means for controlling the heating amount of the heating means in accordance with a signal from the temperature detection means. The temperature control section includes a slope detection section that detects the slope of the temperature rise of the food to be cooked by the temperature detection means with respect to time, and a slope detection portion that detects the slope of the temperature rise of the food to be cooked detected by the temperature detection means. a bending point detection unit that detects a bending point where the time slope of the temperature detected by the slope detection unit becomes less than a predetermined value and outputs a signal; A temperature storage unit stores the output of the temperature detection means as a set temperature, and outputs a signal to the heating control means so as to control the heating amount of the food according to the temperature difference between this and a signal from the temperature detection means. A cooking temperature control device configured to include a proportional control section.