JPH0215891B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control device for a cooker, etc., and in particular, when controlling a temperature close to room temperature such as yeast fermentation temperature, the internal temperature of the cooker is overscalated with respect to the set temperature. This invention relates to a temperature control device that has been improved to eliminate overheating.

Generally, a temperature sensing element for detecting the internal temperature of a cooking appliance is provided outside the cooking appliance or inside a cover that protrudes into the cooking appliance in order to prevent dirt and the like.
For this reason, there is a time delay in the temperature rise of the thermosensor compared to the temperature rise in the center of the refrigerator, which should be controlled.
Particularly, when the set temperature is close to room temperature, the ratio of temperature difference due to this delay becomes large, and the internal temperature largely overshoots the set temperature.
For example, in Figure 1, T ₁ is the temperature detected by the thermosensor, T ₂ is the temperature inside the cooking appliance, and T ₁₀ is the set temperature of the thermosensor, that is, when the thermosensor detects this temperature, T 1 is the temperature detected by the thermosensor. The switching element operates. T ₂₀ is the target temperature inside the refrigerator. Now, when the heater is energized, the internal temperature T ₂ rises, and subsequently the temperature T ₁ detected by the temperature sensing element rises, but there is a time lag between T ₂ and T ₁ , and T ₁ = T When the switching element operates and the heater is cut off at ₁₀ ,
T ₂ greatly overshoots T ₂₀ . Then, as the heater is repeatedly turned on and off, _T2 gradually approaches _T20 .

In such cases, for example, yeast fermentation of bread dough usually results in good fermentation at around 40°C, but if the temperature rises above about 60°C, the bacteria die. In reality, because the temperature inside the oven rises to 60 degrees Celsius or higher due to overshoot for a short period of time, the bacteria on the surface of the bread dough are only killed, but this also results in bread that does not rise well.

In order to solve such problems, conventionally,
When using an electric cooker in the normal high temperature range (130 to 250℃), connect the heaters installed above and below the cooking chamber in parallel and use high power to maintain the yeast fermentation temperature close to room temperature. In the past, heaters were connected in series to achieve low power consumption. In this latter case, the attempt is made to slow down the temperature rise inside the refrigerator and to make the time delay in the temperature rise of the temperature sensing element relatively small, but it is basically impossible to eliminate overshoot. .

Another method is to install an auxiliary heater near the temperature sensing element and use the heat from this auxiliary heater to correct the temperature, but this method is easily affected by voltage fluctuations, and the residual heat of the auxiliary heater As a result, the temperature of the temperature sensing element remains high even when the temperature inside the refrigerator is low, making it difficult to control the temperature with high accuracy.

As described above, in order to prevent an overshoot of the internal temperature, various efforts have been made to bring the temperature rise of the temperature sensing element and the temperature rise within the cooking chamber closer to each other.

In order to eliminate the drawbacks of the conventional example described above, the present invention provides a time limit circuit that specifies the energization time and cut-off time of the heater separately from the temperature detection circuit, and prevents the temperature inside the refrigerator from overshooting. A control device is provided. Hereinafter, embodiments will be described in detail with reference to the drawings.

FIG. 2 shows one embodiment of the present invention.
1 is a power supply circuit, 2 is a temperature detection circuit, 3 is a timer circuit, and 4 is a switching circuit for turning the heater 5 on and off. Then, the time limit circuit 3 determines the maximum time for the heater to be energized (the time when the energization cannot be continued any longer and is forcibly cut off) and the minimum time for the heater to be cut off (the time when the heater cannot be energized for any longer and is forcibly cut off). (time period for which the blockage is to last).

Now, as shown in Figure 3, the temperature detected by the thermosensor is _T1 , the internal temperature of the cooker is _T2 , and the set temperature of the thermosensor at which the switching element operates is T1.
T ₁₀ , target temperature in the refrigerator T ₂₀ , heater energization time t _N , heater cut-off time t _F , maximum heater energization setting time t _N0 , shortest heater cut-off setting time t Assuming _F0 , T ₁ with conventional equipment
> T ₁₀ , but in the present invention, even if T ₁ < T ₁₀ , the heater is shut off when the heater current continues for t _N0 , and this t _N0 is This is set to the time required for the internal temperature _T2 to gradually rise to exceed _T20 .

Next, T ₂ gradually decreases and T ₁ gradually increases due to residual heat, but even if T ₁ < T ₁₀ , the heater is kept shut off for t _F0 , and after this t _F0 elapses,
The heater is energized again. After that, mainly
Temperature control is performed by repeating the operation of shutting off when T ₁ > T ₁₀ and energizing when t _F0 has elapsed and T ₁ < T ₁₀ . In this way, by appropriately setting t _N0 and t _F0 of the timer circuit 3, the
Highly accurate temperature control can be performed.

As explained above, according to the present invention, by incorporating a timer circuit using a microprocessor or an integrated circuit into a temperature control device, additional parts such as a heater connection switch and an auxiliary heater are no longer required. It is possible to control temperatures close to room temperature, which has been considered difficult, with high precision and with inexpensive equipment, and its practical value is extremely large.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of characteristics of a conventional device, and FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention.
FIG. 3 is a diagram showing an example of characteristics according to the present invention. 1...Power supply circuit, 2...Temperature detection circuit, 3...
Time limit circuit, 4... switching circuit, 5... heater.

Claims (1)

[Scope of Claims] 1. A temperature control device that detects the temperature of a temperature-controlled object using a temperature sensing element and operates a switching element to turn on and off the heater, which defines the time for turning on and turning off the heater. A time limit circuit is provided, and the time limit circuit has a maximum time t N0 for heater energization (the time t N0 when energization cannot be sustained any longer and must be forcibly cut off) and a minimum time t _N0 for heater cutoff (the time within which energization cannot be continued). , the duration of forced shutdown)
_tF0 is set, and _tN0 is the time from when the power is turned on until the temperature _T2 of the temperature controlled object exceeds a preset target temperature _T20 , and the temperature detected by the temperature sensing element is T. _1. Set the temperature of the temperature sensing element at which the switching element operates.
T ₁₀ , heater energization time t _N and heater cut-off time t _F , the heater is cut off when T ₁ > T ₁₀ or t _N ≧t _N0 , and T ₁ < T ₁₀ and t _F ≧ t A temperature control device characterized in that the heater is energized at _F0 .