JPS594839B2 - Heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic heater, and particularly provides an automatic heater that automatically controls heating using sensor means sensitive to water vapor emitted from an object to be heated.

Generally, sensors that are sensitive to water vapor emitted from the heated object are installed inside the heating chamber or exhaust duct, so if used for a long time, the sensor may become contaminated by droplets, volatile substances, oil smoke, etc. from the heated object. There is a problem that the initial performance and sensitivity cannot be obtained after 10 uses.

Therefore, a coil heater is installed near the sensor element, and the coil heater is energized immediately after heating to heat the sensor element.
A method has been considered in which the temperature is heated to 0° C. or higher to burn off the adhering dirt and keep the performance and sensitivity at a constant level of 15. By the way, after the cleaning of the sensor is completed and the power supply to the coil heater is stopped, the sensor cannot immediately obtain stable and good detection performance. The reason for this will be explained using the characteristics of the relative humidity detection sensor used in the embodiment of the present invention shown in FIG. 3a. FIG. 3a shows time on the horizontal axis and relative humidity on the vertical axis, and shows the change in relative humidity in the exhaust duct after heating starts. Heating starts from point A, but at the same time cleaning of the sensor also starts, the temperature around the sensor rises rapidly due to the heating of the coil heater, and the relative humidity gradually decreases towards point B. go. Point B is the point at which the sensor section reaches a predetermined temperature and cleaning is completed. Although there is a slight overshoot as the coil heater finishes energizing for 30 seconds at point B, the sensor is now cooled by the exhaust air and the temperature gradually returns to room temperature, so the relative humidity rises towards point C. I will do it. After CAVC is reached and the sensor returns to a steady state, the temperature of the exhaust air 35 gradually increases due to the progress of heating, and therefore decreases toward point D. Point D is the point where the increase in relative humidity due to water vapor emitted from the heated object exceeds the decrease in relative humidity due to the temperature rise of the exhaust air.After this, the amount of water vapor from the heated object increases, so the relative humidity becomes E. point, F point and so on. We detect the relative humidity change in ARH from point D and automatically control heating.

By the way, it is clear from Figure 3a that the amount of change in ARH also occurs between point B and point C until the cleaning is completed and the steady state is returned, but the change in relative humidity during this period is caused by a large amount of It cannot be used to detect heating because it is not caused by water vapor released. Therefore, the detection by the sensor is T. only need to wait. By the way, if we start heating at high output from the start of heating, if the object to be heated is small, a large amount of water vapor will come out until the sensor returns to a steady state, that is, until it reaches Tc. It is conceivable that when this is reached, a situation will arise in which the relative humidity change ΔRH cannot be obtained.

Therefore, as shown in Fig. 3b, the output is zero from the start of heating until Tc, and then the output is increased to high after Tc.
There is a way to solve the problems mentioned above. However, this method has the disadvantage that since no heating is actually performed from the start of heating until Tc, the time required for heating increases by the entire time Tc, resulting in poor time efficiency.

The present invention aims to eliminate the above-mentioned drawbacks and improve time efficiency.

The present invention will be described below with reference to the drawings in an embodiment of a microwave oven. Reference numeral 1 denotes a heating chamber, in which food 2 placed therein is heated with high frequency energy oscillated by a magnetron 3.

A fan motor 4 cools the magnetron 3 and the like, and also blows ventilation air 7 into the heating chamber through the air duct 5 and the air outlet 6.

Exhaust air 9 containing water vapor 8 emitted from food 2 is passed through exhaust port 10
It is discharged to the exhaust duct 11 through. Reference numeral 12 is a relative humidity detection type sensor that is sensitive to the relative humidity of the exhaust air 9.

FIG. 2 shows an enlarged view of the humidity detection type sensor 12. 13 is a sensor element, 14 is a coil heater provided near the periphery of the sensor element 13, and 15 is a support portion made of a ceramic material.

When the food 2 is heated with such a configuration, the relative humidity of the exhaust air 9 changes as shown in FIG. 3a. This is exactly the same as the explanation in the conventional example, but the feature of the present invention lies in the control of heating power. For example, in one embodiment of the present invention, as shown in FIG. 3c, when sensor 12 returns to a substantially steady state, ie, T. Heating starts at high output from t1 before reaching . This shortens the heating time by the time TC-t1, improving time efficiency. However, when setting t1, set t1 to T from food 2, etc. that is actually heated. Care should be taken to ensure that large amounts of water vapor are not produced by high-power heating. FIGS. 4a and 4b show an embodiment of an electric circuit including such a heating power control means. Reference numeral 16 denotes a commercial power source, and 17 a contact inserted into the main circuit, which turns ON when heating starts, and applies voltage to the fan motor 4.

19 is a high voltage transformer, 20 is a high voltage capacitor, and 21 is a stack diode, which serves as an anode voltage source to the magnetron 3.

Reference numeral 23 is a contact point of a high-voltage relay, which changes the anode voltage to the magnetron 3 from 0N to 0FF.

The coil 22 is controlled by a control section 18VC.

Reference numeral 24 denotes a triax, which turns ON-OFF in response to a signal from the control section 18.

With such a configuration, after heating starts and until t1, the high voltage reed relay contact 23 and the triax 24 are turned off.
The magnetron 3 is brought into a state where oscillation is stopped, and after t1, the magnetron 3 is turned ON to oscillate, and heating can be performed at high output.

FIG. 3d shows another embodiment in which the output power is low during the predetermined time T2.
The method is to heat at 1, then switch to high output and heat.

However, the detection of water vapor by the sensor starts from Tc. In this case as well, when setting T2 and low output PL, the determination should be made with the actual object to be heated in mind. FIG. 4c is an electrical circuit including heating power control means for carrying out this method. 26 is the contact point of the power switching relay, and when it is 0N, the first high-voltage capacitor 20 and the second high-voltage capacitor 2' are connected in parallel, so the combined capacitance becomes large, and the high frequency oscillated from the magnetron 3 becomes high output. When it is 0FF, the output is low.

25 is the coil of the power switching relay and the control section 18
is driven by a signal from

FIG. 3e also shows another embodiment, in which heating is performed intermittently during a predetermined time T3 with 0N for T1 and 0FF for T2, and after T3 the heating is switched to continuous operation at high output.

However, detection of water vapor by the sensor will be possible after Tc. In this case as well, when setting T3}, Tl, and T2, the actual object to be heated is taken into consideration. An example of an electrical circuit for this method is shown in FIG. 4a or 4b. As explained above, according to the present invention, the following effects can be expected. 1 According to the present invention, the sensor element is cleaned at the start of heating, so good and stable detection performance can always be obtained, and moreover, the object to be heated can be heated at high output from a time that takes into consideration the actual object to be heated, without waiting until the sensor returns to a steady state. This makes it very time efficient.

2. By the time the sensor returns to its steady state, it is effectively heated at a low output, so a large amount of water vapor does not come out from the heated object during that time, and the heating is very time efficient. equipment can be provided.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a heating device showing an embodiment of the present invention;
Fig. 2 is an enlarged view of the sensor section of the same essential part, Fig. 3a is a characteristic diagram of the sensor, Fig. 3b is a heating pattern showing a conventional example, and Fig. 3c is an implementation of the heating pattern of the present invention. Figures illustrating examples; Figure 3d is the same heating pattern; Figure 3e is the same heating pattern; Figure 4a is the electric circuit diagram of the same heating device;
FIG. 4b is a diagram of another electric circuit, and FIG. 4c is a diagram of another electric circuit. 1... Heating chamber, 3... Magnetron,
4...Fan motor, 10...Exhaust port, 11...Exhaust duct, 12...Relative humidity detection sensor.

Claims (1)

[Scope of Claims] 1. A heating chamber for storing an object to be heated, an air blower for ventilating this heating chamber, an exhaust duct provided for exhausting ventilation air, and a heating chamber provided within this exhaust duct. and sensor means that is sensitive to water vapor emitted from the object to be heated, and means for cleaning the sensor means, and after cleaning the sensor means, the heating power is substantially reduced until the sensor means returns to a steady state. A heater equipped with a heating power control means to lower the output. 2. The heater according to claim 1, wherein the heating is started at zero output, and after cleaning the sensor means, the heating power is switched from zero output to high output before the sensor means returns to a steady state. 3. The heater according to claim 1, which heats at a low output until the sensor means returns to a substantially steady state after starting heating, and then switches to a high output for heating. 4 After the start of heating, until the sensor means returns to a substantially steady state, heating is performed at substantially low output by intermittent repetition of high output and zero output, and then the heating is switched to high output for heating. The heater according to item 1.