JPH0533957Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Field> The present invention relates to a humidity detection device used, for example, to detect the finish of food heated in a microwave oven.

<Prior Art> FIG. 18 is a perspective view of a microwave oven incorporating a humidity detection device. In the figure, 1 is a magnetron, 2 is a high-voltage transformer, and 3 is a cooling fan for cooling the magnetron 1, high-voltage transformer 2, etc., and these are built in the main body 5 outside the heating chamber 4. The heat radiated from the magnetron 1 itself is exhausted from the through hole 6 in the wall of the heating chamber 4 to the exhaust duct 7 together with the hot air a generated by the object to be heated in the heating chamber 4 . A humidity sensor 8 is disposed in the exhaust duct 7 as shown in FIG. 19, and discharges water vapor generated from the heated object inside the heating chamber 4 to the outside of the heating chamber 4.

The humidity sensor 8 includes a first heat-sensitive resistor H that is self-heated or heated by a heating heat source, a second heat-sensitive resistor N that is arranged in parallel with the first heat-sensitive resistor H and detects the humidity in the atmosphere, and the second heat-sensitive resistor N. and a substrate 11 supporting the first heat-sensitive resistor H.

The first heat-sensitive resistance H and the second heat-sensitive resistance N are the 21st
Connect electrically as shown in the figure. That is, a constant current circuit is configured by an operational amplifier OP1, a transistor Q, a resistor RS, and a reference power supply Vref, and a constant current Io=Vref/RS is supplied to the first heat-sensitive resistor H to cause it to self-heat and lower its temperature to the boiling point of water ( By keeping the temperature above 100℃, it has a humidity detection effect.

The semiconductor control resistor (transistor) Q is for amplifying the output current of the operational amplifier OP1. The second heat sensitive resistor N is a heat sensitive resistor for detecting ambient temperature, and the second heat sensitive resistor N is connected to the output of the first heat sensitive resistor H and an operational amplifier.
It is inserted into the inverting input of OP2. operational amplifier OP
2 is for detecting and amplifying humidity. Rf is a feedback resistor that determines the gain of the operational amplifier OP2, and RB is a resistor that bypasses the current flowing through the second heat-sensitive resistor.

FIG. 22 is a humidity detection circuit diagram simply describing the circuit configuration of FIG. 21.

In this configuration, the output voltage Vout is Vout=RH・Io・Rf/−(1−aH・Io ²・RH/hm・S)
・RN...Derived from (1).

However, RH: Resistance of the first heat-sensitive resistor H at 0°C αH: Temperature coefficient Io of the first heat-sensitive resistor H: Constant current source RN: Resistance of the second heat-sensitive resistor N at 0°C Rf: Operational amplifier's resistance Feedback resistor S: surface area of first heat-sensitive resistor H hm: heat transfer coefficient Since hm is constant in a dry state, the output Vout is a constant negative value. As cooking progresses and hm increases due to the steam generated, the absolute value of Vout becomes smaller. The heating time was controlled by detecting the degree of partitioning of the food from this output voltage Vout.

However, in the conventional humidity sensor 8 as shown in FIG. 20, air containing steam unevenly hits the first and second heat-sensitive resistors as shown in FIG.
1, A2 occurs, and also due to changes in wind speed, hm
It was difficult to accurately detect humidity because the humidity changed.

Moreover, when the supply voltage of the microwave oven changes, the rotation speed of the cooling fan 3 changes, and the air volume a of the exhaust air also changes. For example, while cooking in the microwave, turn the cooler on and off, turn on other devices, etc.
The supply voltage of the microwave oven changes due to turning off, etc. In such a case, if the humidity sensor 8 is used for cooking, the temperature of the first heat-sensitive resistor changes.

When the supply voltage of the microwave oven increases, the temperature of the first heat-sensitive resistor 4 decreases. If the wind speed a of the exhaust air is constant, a decrease in the temperature of the first heat-sensitive resistor H can be interpreted as a change in the amount of water vapor contained in the exhaust air a, but if the wind speed of the exhaust air a fluctuates, In this case, it is difficult to determine whether a change in the wind speed of the exhaust air a is a change in the amount of water vapor. Moreover, for this reason, the output signal from the humidity sensor fluctuates as shown in FIG. 24, making accurate measurement difficult.

<Purpose> In view of the above, an object of the present invention is to provide a humidity detection device that enables accurate humidity detection by controlling the wind speed that hits the heat-sensitive resistor.

<Example> Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 1 shows a first embodiment of the present invention, and the humidity detection device according to the present invention is a humidity sensor that detects the humidity in the atmosphere of an air passage as an exhaust duct 7 of a microwave oven shown in FIG. 8 is provided, and the humidity sensor 8 includes a first heat-sensitive resistor H heated by self-heating or a heating heat source, and a first heat-sensitive resistor H
a second heat-sensitive resistor N arranged in parallel to detect humidity in the atmosphere; a substrate 11 supporting the second heat-sensitive resistor and the first heat-sensitive resistor H; and a substrate 11 surrounding the first heat-sensitive resistor H and the second heat-sensitive resistor N. A rectangular parallelepiped rectifier box 12 with an open bottom surface, a rectangular air volume control inlet 13 formed on the front facing plate 12A perpendicular to the airflow direction of the airflow path of the rectification box 12, and and a rectangular air volume control outlet 14 formed in the rear facing plate 12B orthogonal to the rear facing plate 12B.

In the above configuration, the wind C introduced into the rectifier box 12 through the exhaust duct 7 hits the first heat-sensitive resistor and the second heat-sensitive resistor N. For example, the ambient temperature
When the exhaust air containing water vapor at 50°C is applied to the heat-sensitive parts 9 and 10 of the heat-sensitive resistors H and N at 20°C as shown in Fig. 2, the flow velocity of the exhaust air C will be strong if there is no rectifier box 12. Because the flow is not rectified, the exhaust air hits the surface of the heat-sensitive resistor with varying degrees of strength, resulting in temperature unevenness A1 and A2, as shown in FIG. Therefore, the response speed to the temperature of the exhaust air also becomes uneven, and this is the main cause of fluctuations as shown in FIG. 22.

However, when the exhaust air is introduced into the rectifier box 12 to reduce the flow velocity and rectify the exhaust air, the exhaust air hits the entire surface of the heat-sensitive resistor uniformly, as shown in Figure 3, and the heat-sensitive resistor Temperature unevenness and response speed unevenness on the surfaces of H and N are solved.

As a result, the output signal D becomes stable as shown in FIG. Therefore, if a stable output signal is obtained, the heating time can be calculated more accurately.

FIG. 5 shows a second embodiment of the present invention.

If the inlet 13 of the rectifier box 12 is small, there is a possibility that the hole may be blocked by oil, food waste, and other impurities contained in the steam generated as the cooking progresses. In that case, air containing steam will not come into contact with the first and second heat-sensitive resistors H and N, making it impossible to detect humidity.

Therefore, in this embodiment, a plurality of inlets 13a, 13b, and 13c are formed in the front facing plate 12A of the rectifier box 12, and the leg portion 12a of the rectifier box 12 is penetrated by the hole 11a formed in the substrate 11. It is then fixed to the substrate 11 by bending it. The other configurations are the same as those of the first embodiment.

With the above configuration, even if one inlet 13a is blocked by foreign objects, the other inlets 13b and 13c allow the wind C to flow into the rectifier box 12, allowing stable humidity detection. Make it.

In addition, in the first and second embodiments described above, even when the supply voltage changes, since the wind speed becomes slower, output fluctuations can also be reduced. That is, FIG. 6 shows the output voltage Vout when the cooling fan 3 is rotated from a stopped state in the detection circuit of FIG. 21.
These diagrams show the conventional type X and the present invention Y. In the present invention, the wind speed hitting the heat-sensitive resistor is slow, so there is little voltage change.

In addition, Fig. 7 shows that the cooling fan 3 is rotating and the voltage is
This is a characteristic diagram when the supply voltage of the cooling fan 3 changes when Vout is constant. In the figure, X1 shows the conventional case and Y1 shows the case of the present invention. ing.

8 and 9 show a third embodiment of the present invention, in which a horizontally elongated inlet 13 and an elongated outlet 14 are formed near the bottom of the rectifying box 12, and the width of the inlet 13 and the outlet 14 is as follows: The distance between the pair of lead legs 9A and 10A of each heat-sensitive resistor H and N is set to be smaller than that, so that the wind C passing through the rectifier box 12 directly hits the first heat-sensitive resistor H and the second heat-sensitive resistor N. The temperature flow rate is lowered to perform rectification, and hot air is uniformly applied to the entire surface of the heat-sensitive resistors H and N to correct for temperature variations on the surface. The other configurations are the same as those of the first embodiment.

In the above configuration, the wind C entering the rectifying box 12 flows turbulently and licks the entire surface of the heat-sensitive resistors N and H as shown in FIG. 3, so that the exhaust air C hits uniformly.

Here, if the width of the inflow ports 13 and 14 is larger than the width between the pair of lead legs 9A and 10A of each heat-sensitive resistor H and N, the exhaust air passing through the inlet port 13 will directly flow through the lead legs of the heat-sensitive resistors H and N. In the parts 9A and 10A, heat conduction occurs from the lead leg parts 9A and 10A, and the temperature rises first from both ends A1 of the heat sensitive parts 9 and 10, and a temperature difference appears between the center part A2 and the heat sensitive parts 9A and 10A. Therefore, the response speed to the temperature of the exhaust air also becomes uneven, and fluctuations as shown in FIG. 24 appear in the output Vout due to these factors.

However, in this example, the widths of the inlet 13 and outlet 14 are set smaller than the distance between the pair of leader legs 9A, 10A, so the exhaust air entering the rectifier box 12 flows turbulently, causing heat-sensitive resistance. The entire surface of H and N is licked, the exhaust air is uniformly hit, and temperature unevenness and response speed unevenness on the surfaces of the heat sensitive parts 9 and 10 are solved. As a result, the output signal D becomes stable as shown in FIG.

11 and 12 show a fourth embodiment of the present invention, in which the rectifier box 12 is made of metal such as aluminum, which has good thermal conductivity. Note that 14 in the figure is a cross-sectional packing for preventing thermal influence on the substrate 11. The other configurations are the same as those of the second embodiment.

Figure 12 shows the time from when the cooling fan 3 starts rotating until the circuit output stabilizes when the rectifier box 12 is made of polypropylene resin with a thickness of 1 mm and when it is made of aluminum with a thickness of 0.6 mm. It is. In the case of polypropylene resin (W in the diagram)
It used to take about 3 minutes for the circuit output to stabilize, but when it was made of a metal with good thermal conductivity, such as aluminum, it became stable in about 50 seconds.

FIG. 13 shows a fifth embodiment of the present invention.
In this embodiment, a partition plate 16 is provided in a rectifying box 12 to separate a first heat sensitive resistor H and a second heat sensitive resistor N, and an exhaust air communication hole 17 is formed in the partition plate 16. The other configurations are the same as those of the second embodiment.

In the above configuration, the unevenness of the wind C flowing into the rectifier box 12 can be reduced, and the above (1)
It is possible to suppress changes in hm in the equation and accurately detect humidity.

14 and 15 show a sixth embodiment of the present invention, in which synthetic resin coatings 17 and 18 are formed on the first heat-sensitive resistor H and the second heat-sensitive resistor N. , 18 are heat-resistant materials such as silicone resin or polyimide resin, and the legs 9A, 10A of the heat-sensitive resistors H, N are
And the entire heat sensitive parts 9 and 10 are coated. The other configurations are the same as those of the second embodiment.

With the above configuration, the heat capacity of the first heat-sensitive resistor H and the second heat-sensitive resistor N is increased, the change in hm due to wind unevenness is reduced, and the influence of wind unevenness is eliminated.
This prevents fluctuations in the output voltage Vout, provides a stable output voltage, and enables highly accurate humidity detection.

16 and 17 show a seventh embodiment of the present invention, in which the heat-sensitive parts 9 and 10 of the first heat-sensitive resistor H and the second heat-sensitive resistor N are spaced apart from the substrate 11 by 5 mm or more. It is. Note that the other configurations are the same as those of the first embodiment.

When the heat-sensitive resistors H and N are attached closely to the board 11, the cooling fan 3 does not rotate when the microwave oven is not operating, so the exhaust air does not hit the heat-sensitive resistors H and N and the board 11. The substrate 11 is heated by the heat-sensitive resistor H which is self-heating. Thereafter, when the cooking mode is entered, the cooling fan 3 rotates, and the exhaust air from inside the refrigerator hits the heat-sensitive resistors H, N and the substrate 11. The heat-sensitive resistors H and N have short thermal time constants, and reach a thermal equilibrium state approximately 30 seconds after the cooling fan 3 starts rotating.

However, since the substrate 11 has a large heat capacity, approximately 3
It has a thermal time constant of minutes.

Therefore, if the heat-sensitive resistor HN is attached closely to the board 11, it will be affected by the thermal time constant of the board 11 as shown by the solid line W in FIG. It will not be stable until it passes.

However, if the heat-sensitive parts 9 and 10 of the heat-sensitive resistors N and H are separated from the board 11 by 5 mm or more as in this embodiment, the heating of the board 11 by the self-heating heat-sensitive resistor H will be reduced, and the cooling fan 3 When starts rotating, a heat insulating layer of air is formed between the substrate 11 and the heat-sensitive resistors H, N, so that the heat stored in the substrate 11 has very little effect on the heat-sensitive resistors H, N. As indicated by the broken line U in the figure, the circuit output stabilizes in approximately 30 seconds, which is the thermal time constant of the heat-sensitive resistors H and N.

<Effects> As is clear from the above description, the present invention is provided with a humidity sensor that detects the humidity in the atmosphere of the ventilation passage, and the humidity sensor includes a first heat-sensitive resistor that is heated by self-heating or a heating heat source. , a second thermal resistor arranged in parallel with the first thermal resistor to detect humidity in the atmosphere, a substrate supporting the second thermal resistor and the first thermal resistor, and surrounding the first thermal resistor and the second thermal resistor. a rectifying box, an air volume control inlet formed on a front facing plate perpendicular to the air blowing direction of the air passage of the straightening box, and an air volume control inlet formed on a rear facing plate perpendicular to the air blowing direction of the air passage of the straightening box. The present invention relates to a humidity detection device characterized in that it is equipped with an air outlet.

Therefore, according to the present invention, with a simple configuration that only includes a rectifying box with an inlet and an outlet surrounding the heat-sensitive resistor, it is possible to eliminate temperature variations in the heat-sensing part due to the influence of wind variations, and to obtain accurate humidity. It has an excellent effect in making detection possible.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a humidity detection device showing the first embodiment of the present invention, Fig. 2 is a perspective view showing how the exhaust air hits the second heat-sensitive resistor, and Fig. 3 is a perspective view showing the flow of the exhaust air. 4 is a diagram showing the output of the humidity sensor, and FIG. 5 is a perspective view showing the second embodiment of the present invention.
Figure 6 shows the output voltage of the detection circuit when the cooling fan is rotated from a stopped state, and Figure 7 shows the characteristics when the supply voltage of the cooling fan is changed when the output voltage is constant. 8 is a perspective view of a humidity detection device showing a third embodiment of the present invention, and FIG.
The figure is also a front view, Figure 10 is a perspective view showing the temperature unevenness of the heat sensitive part when the exhaust air hits the lead leg of the heat sensitive resistor, and Figure 11 is a humidity detection showing the fourth embodiment of the present invention. Fig. 12 is a perspective view of the device, and Fig. 1 is a diagram showing the relationship between circuit output voltage and fan rotation speed.
3 is a perspective view of a humidity detecting device showing a fifth embodiment of the present invention, FIG. 14 is a perspective view of a humidity detecting device showing a sixth embodiment of the present invention, and FIG. 15 is a cross-sectional view of the same heat-sensitive resistor. Fig. 16 is a perspective view of a humidity detection device according to the seventh embodiment of the present invention, with the rectifier box removed; Fig. 17 is a diagram also showing the output voltage; and Fig. 18 is a perspective view of a general microwave oven. Figure 19 is a side view of the exhaust duct, Figure 20 is a perspective view of a humidity sensor in the prior art, Figure 21 is a temperature detection circuit diagram, and Figure 22 is a simplified version of the temperature detection circuit in Figure 21. FIG. 23 is a side view showing the temperature unevenness state when there is no rectifier box, and FIG. 24 is a diagram showing the output voltage of the humidity sensor when there is no rectifier box. H...First heat sensitive resistor, N...Second heat sensitive resistor, 7
...Ventilation duct, 8...Humidity sensor, 9,10...
Heat sensitive part, 9A, 10A... Lead leg, 11...
Board, 12... Rectifier box, 12A... Front opposing plate, 1
2B... Rear facing plate, 13, 13a, 13b, 13
c... Inlet for air volume control, 14... Outlet for air volume control.

Claims (1)

[Scope of utility model registration request] A humidity sensor is provided to detect the humidity in the atmosphere of the ventilation passage, and the humidity sensor includes a first heat-sensitive resistor heated by self-heating or a heating heat source, and a humidity sensor arranged in parallel with the first heat-sensitive resistor to detect the humidity in the atmosphere. a second heat-sensitive resistor, a substrate supporting the second heat-sensitive resistor and the first heat-sensitive resistor, a rectifier box surrounding the first heat-sensitive resistor and the second heat-sensitive resistor, and an air passage of the rectifier box perpendicular to the air blowing direction. Humidity detection characterized by comprising: an air volume control inlet formed on a front facing plate, and an air volume control outlet formed on a rear facing plate perpendicular to the ventilation direction of the air passage of the rectifier box. Device.