KR900006476Y1 - Heating appiance with humidity sensor - Google Patents

Abstract

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Description

Burner with humidity sensor

1 is a detection circuit for detecting the completion state of the heated object of the heater according to an embodiment of the present invention.

2 is a perspective view of a microwave oven as the present invention heater.

3 is a perspective view of a humidity sensor of the present invention heater.

4 is a humidity detection circuit of another embodiment of the present invention.

5 is a temperature characteristic diagram of VN, VH, and VS when only the ambient temperature is changed as a humidity sensor using heat sensitive elements having different temperature characteristics according to the present invention.

6 is a humidity characteristic diagram of VN, VH, VS when the ambient temperature is fixed and only the humidity is changed.

7 is a temperature characteristic diagram of VN, VH and VS when the humidity is fixed and only the ambient temperature is changed.

* Explanation of symbols for main parts of the drawings

1: humidity sensor 2: controller

3: first thermal element 4: second thermal element

5: comparator 6: control circuit

7: heating chamber 8: exhaust duct

10: first amplifier 11: second amplifier

12: A / D converter 15: High voltage transformer

16 cooling fan 24 detection signal comparator

25: current limiting circuit

The present invention relates to a humidity detection circuit having a humidity sensor for detecting the completion state of the heated object, and more particularly to a heater such as a microwave oven having a humidity sensor for detecting the completion of the heated food.

Conventionally, a humidity sensor used in a microwave oven has been arranged to self-heat two dummysters, enclose one in dry air with an absolute humidity of 0 g / m 3, and the other in contact with the air discharged from the heating chamber.

However, this type of humidity sensor is expensive because it is necessary to use a pair of two dummysters whose temperature coefficients and resistances at high temperatures are approximately equal, and one of them is enclosed in dry air as described above.

The present invention is to provide a humidity detection circuit having a humidity sensor that can detect the humidity at a low price.

Another object of the present invention is to provide an inexpensive humidity detection circuit capable of detecting accurate humidity by configuring a humidity sensor by a thermal element having different temperature characteristics in order to solve the above drawbacks.

The heater has a humidity sensor for detecting the amount of water vapor generated from the heated object and a control device for controlling the heating time according to the output signal of the humidity sensor. The humidity sensor includes a first heat sensing element for detecting an ambient temperature and a self-heating or And a second heat sensing element heated by a heating member, and the control device includes a comparator for comparing the temperature difference between the first heat sensing element and the second heat sensing element generated by water vapor generated from the heated object, and an output signal of the comparator. It consists of a control circuit which computes a subsequent heating time by the time from the start of heating to reaching the predetermined value when the predetermined value predetermined for each heated object is reached.

Furthermore, the humidity detecting circuit of another embodiment of the present invention has a humidity sensor for detecting humidity in the atmosphere, and the humidity sensor has a first heat sensing element for detecting an ambient temperature and a second heat sensing element heated by a self heating or heating heat source. And a comparator for comparing the detection signal of the first heat sensing element and the detection signal of the second heat sensing element, wherein the first heat sensing element and the second heat sensing element have a constant amount of change in voltage at both ends of the atmosphere It is characterized by having different temperature characteristics, respectively, so as to be equivalent when only the temperature is changed.

An embodiment of the present invention will be described with reference to FIGS. 1 to 3, in which the heater according to the present invention has a humidity sensor 1 for detecting an amount of water vapor generated from a heated object and an output signal of the humidity sensor 1. In the heater provided with a control device (2) for controlling the heating time by the humidity sensor (1) is a first thermal element 30 for detecting the ambient temperature and the second thermal element (heated by a self-heating or heating heat source) 4) and the control device 2 comprises a comparator 5 and a comparator for comparing and amplifying the temperature difference between the first heat sensing element 3 and the second heat sensing element 4 generated by water vapor generated from the heated object. When the output signal of (5) reaches a predetermined value predetermined for each object to be heated, it is composed of a control circuit 6 which calculates the subsequent temporary time by the time from the start of heating until reaching the predetermined value. will be.

1 shows the configuration of a detection circuit that detects a completed state of a heated object.

The first thermal element 3 and the second thermal element 4 are composed of a metal thin film resistor, a dummyster or a semiconductor, and the like is used to discharge water vapor in the heating chamber 7 of the microwave oven out of the heating chamber as shown in FIG. It was arranged in the exhaust duct 8.

The first thermal element 3 and the second thermal element 4 were installed in an exposed state on a mounting substrate 9 provided in the duct 8 as shown in FIG.

The first thermal element 3 has a function of measuring the temperature of the exhaust wind containing water vapor discharged from the heating chamber 7, and the second thermal element 4 is heated to high temperature by magnetic heating.

Of course, the second thermal element 4 may maintain the thermal element temperature at a high temperature by means of a heating heat source such as a heater, in addition to the method of self heating.

Next, the reason why the humidity is detected by the configuration of the present invention will be described using a thin film thermal element as an example.

The basic principle is the same as that of the hot wire flowmeter, and in the thermal equilibrium state in which the heat generation temperature of the second heat sensing element 4 does not change, the energy conservation side of the formula (1) is always established.

qg: calorific value per unit volume, qt: cooling heat transfer amount per unit area, the left side is the amount of heat generated by the second heat sensing element 4 per unit time, and the right side is transmitted to the exhaust wind on the surface of the second heat sensing element 4 The heat transfer amount is displayed.

Applying Freie's law and Ohm's law, which are well known in electrothermal engineering, to equation (1),

sss p · J ² dv = ssh · (Tw-Tf) ds ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (2)

p: battery resistivity of the second thermal element 4, J: current density h: local heat transfer coefficient Tw: wall temperature of the second thermal element 4 Tf: temperature of air discharged from the heating chamber (2) if,

RH ・ I ² = hm · (Tw-Tf) · s ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (3)

RH: electrical resistance of the second thermal element 4, I: current flowing through the second thermal element 4, hm: average heat transfer coefficient, s: surface area of the second thermal element 4, and average heat transfer coefficient It depends on the average wind speed of the exhaust wind and also on the amount of water vapor contained in the exhaust wind.

Since the average wind velocity is determined uniquely when the exhaust system of the microwave oven is determined, the average heat transfer coefficient changes according to the amount of steam contained in the exhaust wind.

If Tw is constant, Tf is measured by the first heat sensing element 3 and the resistance value RH or the current value I of the second heat sensing element 4 is obtained, whereby hm is obtained, thereby obtaining the amount of water vapor contained in the exhaust wind.

In other words, if the voltage drop of the second thermal element 4 of FIG.

V = RH ・ I ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 4

I = V / RH ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ 4

Vref = (RL2 + RH) ・ I ‥‥‥‥‥‥‥‥‥‥‥‥‥ 5

In formula (4),

RH and I are obtained, and accordingly, hm of the formula (3) is measured, so that the amount of water vapor contained in the exhaust wind can be known.

A detection circuit embodying the above principle is shown in FIG.

That is, the detection circuit A inputs a voltage to the negative terminal by the second heat sensing element 4 and the current limiting resistor RL2, and inputs a reference voltage of the resistors R1 and R2 to the positive terminal. The voltage of the first amplifier 10, the first thermal element 3, and the current limiting resistor RL1, which detects a voltage change across the thermosensitive element 4, is input to the negative electrode terminal, and the resistor R3 (R4). The second amplifier 11 which detects the change of the voltage of the both ends of the 1st thermal element 3 by inputting the reference voltage by (c) into the positive terminal.

The output side of the first amplifier 10 is input to the negative terminal of the comparator 5, and the output side of the second amplifier 11 is input to the positive terminal of the comparator 5.

In the comparator 5, the differential voltage of the voltage change of both ends of the first thermal element 3 and the second thermal element 4 is referred to as an analog digital converter 12 (hereinafter referred to as an A / D converter 12). It was connected to the said control circuit 6 via it.

The control circuit 6 is mainly a microcomputer and has a data random access memory (RAM), a program read-only memory (ROM), an arithmetic logic unit (ALU) inside, and is driven by a reference clock oscillation circuit. will be.

The control circuit 6 is connected with a setter 13 for setting the type of the heated object to be heated, which outputs the signal from the A / D converter 12 and the setter 13 from the control circuit 6. On the basis of the time taken from the start of heating to the predetermined value when the predetermined value determined for each heated object is reached by the signal, the remaining heating time of the heated object is calculated and the heating means 14 ( Magnetron or heater) to output a stop signal.

In the figure, R5 to R13 are resistors for adjusting amplification.

In addition, 14A is a magnetron, (15) is a high pressure transformer, (16) is a cooling fan for cooling the magnetron (14A) and the high pressure transformer (15), and they are the main body (17) other than the heating chamber (7). Is built in.

In addition, the heat dissipation of the magnetron A itself is configured to be exhausted to the exhaust duct 8 together with the warm air a generated from the heated object in the heating chamber 7 at the seal wall through hole 18 of the heating chamber 7.

Moreover, the temperature sensor may be any place as long as it is an exhaust system for discharging water vapor generated from the heated object heated in the heating chamber 7 to the outside of the heating chamber 7 as well as the above place.

In the above configuration, the water vapor generated by the heating of the heated object is exhausted to the exhaust duct 8.

The humidity sensor 1 in the exhaust duct 8 detects the completion state of the heated object detecting this amount of steam.

In other words, the first amplifier 10 detects the change in the voltage across the second thermal element 4 and the second amplifier 11 detects the change in the voltage across the first thermal element 3. That is, the temperature change of the positive thermal elements 3 and 4 is detected.

The voltage difference between the voltage changes at both ends of the first thermal element 3 and the second thermal element 4 is amplified to a voltage capable of A / D conversion by the comparator 5 and the output is controlled by the A / D converter 12. Input to the circuit 6.

In the control circuit 6, when the input data reaches a predetermined value determined for each heated object, the control circuit 6 switches to the output of the microwave determined for each heated object and based on the time required to reach a predetermined value from the start of the aperture. Calculate how much time you want to heat the heated object after.

When the time comes, a stop signal is outputted to the heating means 14 to end the heating.

Moreover, the present invention is not limited to the above embodiments, and many modifications and changes can be made to the above embodiments within the scope of the present invention.

As is clear from the above description, an embodiment of the present invention provides a humidity sensor for detecting an amount of steam generated from a heated object, a control device for controlling a heating time according to an output signal of the humidity sensor, and the humidity of the heater. The sensor is formed of a first heat sensing element for detecting an ambient temperature and a second heat sensing element heated by a self-heating or heating heat source, and the control device includes a first heat sensing element and a second heat sensing caused by water vapor generated from a heated object. Comparing the temperature difference between the devices and when the output signal of the comparator reaches a predetermined value predetermined for each object to be heated, the subsequent heating time is calculated based on the time from the start of heating until the predetermined value is reached. A heater comprising a control circuit.

Therefore, according to the present invention, even when one thermosensitive element of the humidity sensor is not enclosed in the absolute humidity of 0g / m3 dry air, the first thermosensitive element generates one atmosphere and heats the second thermosensitive element. There is an excellent effect that it is possible to manufacture at such a low price.

Next, another example of the humidity sensor for detecting the amount of steam generated from the heated object used in the above embodiment will be described as the humidity detection circuit.

In the present invention, the humidity detection circuit of another example is provided with a humidity sensor 1 for detecting humidity in an atmosphere, and the humidity sensor 1 is provided with a first heating element 3 for detecting an ambient temperature and a magnetic heating or heating heat source. And a comparator 24 for comparing the detection signal of the first heat sensing element 3 with the detection signal of the second heat sensing element 4, the second heat sensing element 4 being heated by the first heat sensing element. The element 3 and the second heat sensing element 4 have different temperature characteristics, so that the change amounts? VH and? VN of the voltages VN and VH at both ends thereof become equal when only the ambient temperature is changed in a constant humidity.

The difference VN between the voltage between the current limiting resistor R1 'and the first heat sensing element 3 is input to the positive terminal of the comparator 24, and the current limiting circuit is input to the negative terminal of the comparator 24. The difference VH between the voltage between both ends 25 and the second thermal element 4 is input, and the output voltage VS of the comparator 24 is the difference voltage between the first thermal element 3 and the second thermal element 4. Is output.

In addition, the current limiting circuit 25 has a function of keeping the surface temperature of the second heat sensing element 4 on the heating side constant, and the first heat sensing element 3 and the second heat sensing element 4 are supplied with a DC constant voltage. have.

However, the humidity detection method in which the humidity sensor is composed of two thermal elements having the same temperature characteristics will be described taking the case of the thermal element as a dummyster.

When the voltage at both ends of the second heating element on the heating side is VH and the voltage at both ends of the first heat sensing element on the ambient temperature measurement side is VH, the potential difference between VH and VN is the output voltage VS of the sensor.

The characteristics of VH, VN, and VS when the ambient temperature is constant and the humidity is changed and when the humidity is constant and the ambient temperature are changed are shown in FIGS.

First, the change characteristic of VN, VH, and VS in the case of constant ambient temperature is explained in FIG.

[Voltage VN between First Heat Sensing Element] The first heat sensing element for measuring the ambient temperature has a small conduction current, and therefore, its resistance is determined by the ambient temperature without self heating.

For this reason, the voltage VN at both ends of the first heat sensing element becomes constant.

Regarding the Voltage VH between the Second Heat Sensing Element When the humidity is 0 g / m 3, the heated second heat sensing element is in a thermal equilibrium state according to the next equation in which Equation (3) is modified.

VH ² / RH = hm (Tw-Tf) ・ S ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ （‥

VH: The case where the voltage at both ends of the heated second thermal element is constant, and when the atmospheric humidity is increased, the average heat transfer coefficient hm becomes large and the right side of Equation 3A becomes large.

In order to obtain thermal equilibrium, increase the left side as the right side increases.

Since the surface temperature of the second thermal element is constant by the current limiting circuit, the resistance of the second thermal element is kept constant.

As a result, the voltage VH across the second thermal element increases.

Regarding the voltage VN across the first thermal element When the ambient temperature rises, the resistance of the first thermal element decreases with the ambient temperature, and the voltage VN across the first thermal element decreases.

[Voltage Both Ends of Second Thermal Element VH] When the atmospheric temperature rises in the state of thermal equilibrium according to Eq. (3A), the right side of Eq. (1) becomes small.

In order to obtain thermal equilibrium, the voltage VH at both ends of the second heat sensitive element on the left side of Equation (1) becomes small.

[Output voltage VS] The rise of the ambient temperature is ΔT.

When the amount of heat of dissipation given to the heated second heat sensing element is ΔH, ΔH = hm · ΔT.

In order to obtain thermal equilibrium, when the change in the voltage VH across the second heat sensing element is ΔVH and the change in the supply heat quantity is ΔQ, ΔQ = ΔVH ¹ / RH.

The change in voltage VN between both ends of the first heat sensing element for measuring the one atmosphere temperature is ΔVN.

In the case of the heat-sensitive element having the same temperature characteristic, the heat amount given to the first heat-sensing element for measuring the ambient temperature is ΔH, but ΔH is also given the heat amount in the second heat-sensing element on the heating side.

However, ΔVN and ΔVH are not equal because supply calories ΔQ are applied to obtain thermal equilibrium.

As a result, the output voltage VS is thermally affected.

That is, the output voltage VS of the humidity sensor is affected by both humidity and ambient temperature.

Atmosphere containing water vapor generated from foods for the completion of heaters, such as microwave ovens, increases the amount of water vapor at the same time as heating proceeds, but rises to ambient temperature and cannot detect humidity accurately, which is a factor for misjudgment of food completion.

Therefore, in the present invention, when only the ambient temperature is changed, ΔVH and ΔVN are made equal by using two first thermal element 3 and second thermal element 4 having appropriately different temperature characteristics.

As a result, as shown in FIG. 5, the output VS of the comparator 24 is not affected by heat, and only the humidity can be detected.

Moreover, the present invention is not limited to the above embodiments, and many modifications and changes can be made to the above embodiments within the scope of the present invention.

As is apparent from the above description, in another embodiment of the present invention, a humidity sensor for detecting humidity in an atmosphere is provided, and the humidity sensor is a first heat sensing element for detecting an ambient temperature and a second heating element by a self heating or heating heat source. And a comparator for comparing the detection signal of the first thermal element and the detection signal of the second thermal element, wherein the first thermal element and the second thermal element have an amount of change in voltage VN (VH) at both ends. (ΔVN) (ΔVH) relates to a humidity detection circuit characterized by retaining different temperature characteristics so that they are equal when the humidity is constant and only the ambient temperature is changed.

Therefore, according to the present invention, by constructing a humidity sensor with two thermal elements having different temperature characteristics, it is possible to accurately detect humidity without being affected by heat, and at the same time, one thermal element can be enclosed in dry air as in the prior art. There is an excellent effect that can be configured at a low price without the need.

In the embodiment of the present invention, the heater is described with reference to a microwave oven, but may be applied to various other devices such as a dryer.

In the humidity sensor used in the present invention, the second thermal element that generates heat at a high temperature deprives heat in proportion to the amount of water vapor contained in the air.

Detects the amount of heat lost and detects the amount of water vapor in the air

The first thermal element measures the temperature of the air and corrects the thermal change due to the temperature of the second thermal element.

Claims (15)

A humidity sensor for detecting humidity in an atmosphere having a first thermal element for detecting an ambient temperature and a second thermal element for heating, and a detection signal of the first thermal element and a second thermal element for determining humidity in an atmosphere Comparator for comparing detected signals. The heater according to claim 1, wherein the heater has a humidity sensor which measures a temperature in the atmosphere of the first heat sensing element and outputs a signal for correcting a heat change caused by the temperature of the second heat sensing element. The heater of claim 1, wherein the heated second heat sensing element has a humidity sensor that detects moisture in the atmosphere by measuring a heat amount proportional to the amount of water vapor contained in the atmosphere. The heater according to claim 1, wherein said first and second thermal elements each have a humidity sensor having different temperature characteristics such that the amount of change in voltage across both ends is equal when the humidity is constant and only the ambient temperature is changed. The heater of claim 1, wherein the second heat sensing element has a humidity sensor that is heated by self-heating. The heater according to claim 1, wherein a heating source for generating the second heat sensing element is provided separately from the second heat sensing element. The heater of claim 1, wherein the humidity sensor has a humidity sensor that detects an amount of water vapor generated from a heated object. The heater of claim 1, wherein the humidity detection circuit has a humidity sensor used for the heater. According to claim 8, wherein the control device for controlling the heating time based on the output signal of the humidity sensor is installed and the output signal of the first thermal element and the second thermal element generated by the steam generated from the heated object A discrimination circuit for discriminating whether or not the output signal of the comparison circuit and the comparison circuit has reached a predetermined value determined for each heated object, and when it is determined that the discrimination circuit is a predetermined value, A heater having a humidity sensor, which is composed of a calculation circuit that calculates a subsequent heating time based on the time until reaching. 9. The heater of claim 8, wherein the first thermosensitive element measures a temperature in the atmosphere and outputs a signal for correcting a thermal change caused by the temperature of the second thermosensitive element. 9. The heater of claim 8, wherein the heated second heat sensing element has a humidity sensor that measures heat in comparison with the amount of water vapor contained in the atmosphere to detect humidity in the atmosphere. 9. The heater according to claim 8, wherein the first and second heat sensing elements each have a different temperature characteristic so that the amount of change in the voltages at both ends thereof is equal when the humidity is constant and only the ambient temperature is changed. 9. The heater of claim 8, wherein the second heat sensing element has a humidity sensor that is heated by self-heating. The heater according to claim 8, wherein a heating source for generating the second heat sensing element is provided separately from the second heat sensing element. 9. The heater of claim 8, wherein the humidity sensor has a humidity sensor that detects an amount of water vapor generated from a heated object.