JPH028217B2 - - 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 done by hand, 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 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 reached, the temperature of the contents will never reach the set temperature no matter how long it takes (water is 100°C 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 the slope of temperature rise of the food to be cooked, and a slope detection unit that calculates the degree of change in temperature slope as the food boils, and calculates this value. A bending point detection section for detecting a bending point at which the curve becomes a predetermined value is provided, and the amount of heating is controlled by a boiling detection signal from the bending point detection section.

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. It has the effect of accurately detecting whether the food has boiled even if the amount of food is not boiling or the amount of food is different.

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
At room temperature, both curves A and B rise due to heating, and at temperature Tb, the rising curve becomes gentler and begins to rise again. This is because the moisture condensed around the container evaporates at the temperature Tb, which 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 △X
The bending point detection unit 9 measures the temperature change ΔT at each
determines that the point where the degree of change in the slope value △T reaches a certain level, that is, the ratio of the slope value measured this time to the slope value measured last time, is the inflection point, and then calculates the temperature Td at that point. is determined to be the sensor temperature when the content temperature reaches 100℃. Here, as the degree of change of △T, the latest slope value and △Tn
The ratio of the slope value △T(n-1) measured one time ago to △
The configuration is such that Tn/ΔT(n-1) is calculated, and specifically, the following equation is calculated.

{Tn-T(n-1)}/{T(n-1)-T(n-
2)} Tn is the latest measured temperature of the sensor, T(n-1) is the previous sensor temperature (time △X ago), T(n-
2) is the sensor temperature two times before. This formula is not limited to this form; it may use values from three or four times before, or it may be a form that calculates the difference rather than the ratio of slope values to calculate the degree of change in slope values. Any arithmetic expression that can be used may be used.

The purpose of calculating the degree of change of this slope value △T is
Due to the difference in slope value △T depending on the amount of food to be cooked, for example, when there is less food to be cooked, the slope value △T is large;
Since the slope value △T becomes smaller when there is a large amount of food to be cooked, if the method determines the point at which the slope value △T itself falls below a certain value as the bending point, the level at which the bending value is determined will differ depending on the amount of food cooked. This is to prevent the determination that the inflection point is determined to be slow when there are few things to be cooked, and quickly when there are many things to be cooked.

In addition to the method of measuring the temperature rise at regular intervals, the slope value ΔT may be determined by the length of time during which the temperature rises at a constant rate.

The heating control unit 10 (described here as a proportional control unit that continuously variably controls the amount of heating) can shift to various types of control based on the signal from the bending point detection unit 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 I 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 I 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 section 10 controls this temperature Te.
The proportional valve current I is increased to Ie according to the difference between the temperature Td and the set temperature Td. As a result, the amount of combustion increases and the temperature A
The temperature returns to the original temperature Tc, and the combustion amount returns to the minimum combustion amount. 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.

Further, 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 Tb, 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 flowchart when the control system described in FIGS. 1 to 4 is created using a microcomputer.

In FIG. 6, IG at step 101 is a subroutine for the ignition sequence of burner 3, and _S1 at steps 103 and 117.
is a subroutine to read the temperature _S1 of the sensor 6, △X in step 109 is a subroutine to set the sampling time, and _S2 in step 119 is the temperature difference Td- _S1
A subroutine for determining the throttle amount of the proportional valve 2 according to the magnitude of the current I and outputting the current I is shown.

After ignition in step 101, the temperature of the sensor read in step 103 is determined as the maximum combustion output in step 102.
Until S ₁ reaches the temperature Tf, which is set higher than the unstable temperature Tb section explained in FIG _.
>Wait for Tf.

If it is determined in step 104 that S ₁ >Tf, partial inclination detection is started. Here, the temperature _S1 of the sensor 6 measured as explained in Fig. 3 is taken step by step.
It is stored every sampling time △X set in step 109. In other words, when the temperature _S1 of the sensor 6 is measured in step 103, in step 105 the memory of the sampling temperature two times before is erased and the temperature at the time of the first sampling is stored as the temperature two times before. (T _o-2 ← T _o-1 ), and in step 106, the value measured during the previous sampling is re-stored as the previous temperature (T _o-1 ← T _o ). Further step 107
The temperature S ₁ measured this time is stored as the current value T _o (T _o ←S ₁ ). 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=(T _o −T _o-1 )/(T _o-1 −T _o-2 ) In other words, Tp is the difference between the current measurement value and the previous measurement value, and the difference between the previous measurement value and 2 This means finding the ratio to the difference between the previous measurement values. Detection of bending points is
When the value of Tp becomes smaller than a predetermined value P, that is, the point at which the increase in each sampling temperature becomes smaller is determined to be the inflection point.

If the condition Tp<P is not satisfied in step 108, the next sampling time ΔX is measured and stored again in a loop.

After it is determined in step 108 that 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 of the proportional control valve is determined according to the temperature difference before detecting the inflection point in step 110, that is, the difference between the first temperature and the second temperature (T _o-1 − _{T o-2} ). The combustion is performed in accordance with the proportional valve current determined in step 114 by changing the quantity Id into three stages as shown in steps 111 to 113 (see FIG. 4W). This is because if the slope is large, the amount of cooking is small, so the minimum amount of combustion is also reduced (Id'') to reduce the chance of burning the food, and if the slope is small, the amount of cooking is determined to be large, so the minimum amount of combustion is Increase (Id′),
The purpose is to prevent it from getting too hot. Furthermore, in step 115, the proportional control section determines the sensor temperature T _o-1 immediately before detecting the bending point as explained in FIG.
is stored as the set temperature Td, and from now on, the difference between this Td and the sensor detection temperature _S1 read in step 117, Td-
_S1 is detected in step 118, and the throttle amount of the proportional valve ₂ is determined in subroutine S2 of step 119 so that the difference Td- _S1 becomes zero, and the proportional control valve is driven. In other words, if the temperature difference Td-S ₁ is large, the burner will increase the combustion amount because the food is getting cold, and if Td-S ₁ is zero or a negative value, the food has not boiled sufficiently. Assuming that there is a minimum aperture amount Id.

Note that X _END in step 116 indicates a program for stopping combustion of the burner when a preset cooking time X ends.

The effects of the above-mentioned embodiments are that by using a method for detecting inclination that determines the difference in sensor temperature by sampling at fixed time intervals, control using a microcomputer, etc. becomes easier, and the process can be performed simply by processing a program. Accurate inclination detection is possible and the system can be configured very easily. In addition, by configuring a proportional control section that proportionally controls the proportional valve using the temperature of the sensor at the bending point as the set temperature, once it has boiled, it can automatically switch to low heat and simmer while maintaining that temperature. If the temperature drops due to the addition of heat, etc., the combustion amount will be automatically increased and the original temperature will be 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.

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

(3) In addition, since the bending point detection is configured to calculate the change in slope degree such as the ratio or difference of slope values, and determine the point where this value becomes less than a predetermined value as a bending point. , even if there is a difference in the slope value itself, such as when the amount of cooking is small and the slope value is large, and when the amount of cooking is large and the slope is small, the level at which the inflection point is determined does not change and the inflection point is accurate. It becomes possible to judge.

[Brief explanation of drawings]

FIG. 1 is a control system diagram showing one embodiment of the cooking temperature control device 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.
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 proportional control system using pot bottom temperature detection. Control system diagram, No. 6
The figure is a schematic flowchart showing an example in which 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 (heating control part), Td...
Set temperature, Tf...measurement start temperature, P...predetermined value, △T...slope value, △X...sampling time,...slope change calculation section.

Claims (1)

[Claims] 1 A control signal is sent 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 for detecting the slope of the temperature rise of the food to be cooked detected by the temperature detection means. a bending point detection section for detecting a bending point at which the temperature becomes gentle and a value of a slope change calculation section that calculates the degree of change in the time slope of the temperature detected by the slope detection section becomes a predetermined value; A cooking temperature control device comprising a heating control section that varies or stops the heating amount of the heating means based on a signal output from a point detection section.