JPS59221531A - Electronic range - Google Patents

Abstract

PURPOSE:To make it possible to obtain a desired heating and finishing state even when dews are condensated within a heating chamber at the time of low temperatures by detecting the dewing state within the heating chamber the variation ratio of the output of the AH sensor and varying the time for restoring the initial value of the AH sensor responsive to the dewing state. CONSTITUTION:An output voltage A1 at a common output terminal 20 of resistors R3 and R4 of a bridge B is measured (S3). In a case where A1 is greater than 3, an output voltage A2 of the AH sensor after a time T1 from the start of heating is set to A2 (tau1). An output voltage A2 of the AH sensor after a time T2 from the start of heating is set to A2 (tau2) and these numerical values are stored (S6) and (S7) in RAM22c. These numerical values are operated (S8) as alpha=A2 (tau2)/A2 (tau1). In a case where the value of alpha is greater than 1 it is not enough for generating dews. Further, in a case where alpha is less than 1, the interior of the heating chamber is in a dewing state, and an initial value read-in time T0 is set (S9) to 32 seconds and assumes a time longer than the ordinary read-in time.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a microwave oven that automatically controls heating in response to a detection signal from an absolute humidity sensor.

<Prior Art> First, a microwave oven equipped with an absolute humidity sensor will be briefly described.

Fig. 1 is a front view of the microwave oven, and Fig. 2 is a schematic sectional view thereof. A heating chamber 7 is provided with a tray 6 at the bottom on which the food 5 to be heated is placed, and the food 5 is heated and cooked by microwaves emitted from a magnetron 8 provided at the top of the heating chamber 7. be done. During heating, outside air is sent in by a fan 9, and oil smoke and water vapor from the food 5 are passed through an exhaust passage 10.
Exhausted to the outside via. II is an absolute humidity sensor (hereinafter referred to as "AH sensor") disposed in the exhaust passage 10.
) and detects the finish of the food 5.

As shown in FIG. 3, the external structure of this AH sensor 11 is an open type in which air freely flows inside above the terminal block 12 which forms the attachment part to the exhaust passage 10 and fixes the four lead terminals. The sensor 13 and a sealed sensor +4 whose interior is isolated from the outside air are provided in contact with each other, and in order to equalize the heat of these two sensors 13 and 14, a cylindrical heat equalizing tube 15 made of, for example, brass is used to connect the pair of sensors. 13 and 14 are connected, and a wire mesh 16 is covered to protect a part of the sensor.

Figure 4 shows the open type sensor 13 and the closed type sensor 14.
Is this a cross-sectional diagram showing the internal structure of the Ryosen? -13', +
Glass-coated bead-type thermistors 13a and 14a of about 0.5φ are used as the four common sense parts, and two thermistors with well-matched characteristics are selected. These bead type thermistors 13a and 14a each have a thin platinum wire 13
b, +4'b to hermetically connected terminals 13c, 14c
can be attached to. Then, the open type sensor 13 is covered with a metal case 13e in which a ventilation hole +3d is formed.
While the joint is welded to form a temperature detection element, the closed type sensor 14 has the same configuration as the open type sensor described above.
The cylindrical heat-equalizing tube 15 is provided with a vent hole 13d by attaching a metal glass (4-e) with no ventilation holes, introducing dry air into it, and welding the joints to form a temperature compensation element. Holes 15a are formed at corresponding locations.The thermistor humidity sensor measures absolute humidity using the difference in thermal conductivity between humid air and dry air. As shown in the figure.

In the figure, R1 is a humidity detection element corresponding to the open type sensor 13 equipped with a ventilation hole lid, and R2 is a temperature compensation element corresponding to the closed type sensor 14 sealed with dry air. E is a constant voltage power supply, R3 and R4 are resistors forming bridge circuit B, and R5 is a resistor connected in series with bridge circuit B, which functions to limit the magnitude of the flowing current. The resistance value is selected so that the temperature is about 200°C.

Now, the AI sensor 11 consisting of the resistors R1 and J is placed in a dry air atmosphere, and the resistance values of the resistors R3 and R4 are adjusted so that the output V of the bridge circuit B becomes zero. next,
When this AH sensor In-ff1i is placed in the atmosphere and the relationship between its output V and absolute humidity is investigated, the absolute humidity and the output of the AH sensor 11 have a linear relationship, although not shown. Absolute humidity can be read directly from the sensor output. Considering this qualitatively, the thermistors 13a and 14a of the above AH sensor are both 15
The thermistor 13a of the sensor 13, which is self-heated to 0°C to 200°C and has a ventilation hole, receives air containing water vapor (humid air) due to changes in humidity, and its thermal conductivity is higher than that of the sensor containing dry air. Compared to the thermistor +4a of No. 14, the amount of water vapor itself varies greatly. Tsumashi,
The thermistor 13a exposed to the humid air is cooled, and the balance of the bridge where the resistance value of the resistor R1 is large is lost. This imbalance results in absolute output with linearity.

Next, to explain the output characteristics of the AH sensor I+ when the AH sensor 11 having the above characteristics is incorporated into the microwave oven I, FIG. 6 is a diagram showing the output characteristics of the general AH sensor 11 at normal temperature and humidity. Therefore, when heating food, etc. is left in the heating chamber 7, even if the inside of the heating chamber 7 is in a high humidity state, the heating can be started.The fan motor 28 operates for a predetermined period of time and performs a so-called cleaning operation. The output value A2 of the AH sensor 11 becomes approximately constant from the end of cleaning after water vapor etc. in the heating chamber 7 is discharged and the initial value 'A20 of the AH sensor I+ is maintained in a stable state.
However, as shown in Figure 7, when the ambient temperature becomes low and condensation is likely to occur in the heating chamber 7, the condensed water vapor evaporates as soon as the microwave heating is started after cleaning and the humidity increases. increases, and the output level of the AH sensor 11 rises as shown in ■. Therefore, microwave heating is performed after cleaning, and the finished detection level of the food corresponding to each cooking menu and the above AH
When comparing the output value of the sensor 11, as mentioned above, there is a tendency for the finishing time to be faster than the actual finishing time due to the influence of dew condensation that occurs in the heating chamber in a high humidity state at low temperatures, and there is a disadvantage that the finishing time is unheated. there were.

<Purpose> The present invention has been made in view of the above-mentioned points, and an object of the present invention is to obtain a desired heating finish state even if dew condensation occurs in the heating chamber at low temperatures.

<Configuration> In order to achieve the above-mentioned object, the present invention detects the dew condensation state in the heating chamber based on the rate of change in the output of the AH sensor, and stores the initial value of the AH sensor according to the dew condensation state. <Example> Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 8 is a circuit diagram of a main part of a microwave oven showing an embodiment of the present invention, FIG. 9 is a characteristic diagram explaining the operation of the AH sensor in FIG. 8, and FIG. 10 is an overview of the operation of the present invention. It is a flowchart.

In the figure, parts having the same functions as those of the conventional example described above are given the same reference numerals and detailed explanations will be omitted.

17 is a DC amplifier into which the output voltage V of the bridge circuit B is introduced, and is connected to the Φ converter 18. 1
9 is a ~Φ converter connected to the common terminal 20 of the resistors R3 and R4 of the bridge circuit B. Above ~ Raw converter 1
8 and 19 are connected to the microcomputer 22 via an interface 21, respectively. The microcomputer 22 includes a CPU 2 which is the main body of calculation and control.
2a, a ROM 22b that stores programs and data for calculation and control processing, and a RAM 22c that stores external programs and is used for registers, flags, and the like.

23 is a transistor that operates according to the output of the microcomputer 22; 24 is a relay having a relay coil connected in series with the transistor 23; its contact 25 is connected to a commercial power line 26 that supplies power to the magnetron 8; 27 is a fan motor 2 for a fan 9 that blows air into the heating chamber 7.
8 is a transistor in which a relay coil 30 having a relay contact 29 for controlling ON/OFF is connected in series,
When the menu selection key 3 and heating start key 4 on the operation panel 2 are pressed, the rHighJ signal output from the microcomputer 22 via the interface 21 turns on the relay 30 (which activates the fan motor 28,
A so-called cleaning operation, in which hot air, water vapor, etc. remaining in the heating chamber is sent out of the heating chamber, is started and is set to operate for a predetermined period of time.

Next, the operation of the embodiment of the present invention having the above configuration will be explained based on FIGS. 9 and 10 above.

First, when you press the menu selection key 3 on the operation panel 2 and then press the heating start key 4 (S+), the rHighj signal output from the microcomputer 22 via the interface 21 turns on the relay 30 and starts the fan motor. 28 is activated and a so-called cleaning operation is started (S2) t to send relatively high-temperature air, water vapor, etc. remaining in the heating chamber to the outside of the heating chamber.

Next, it is determined whether or not the inside of the power p heat chamber 7 is at a high temperature, that is, whether the atmosphere in which the AH sensor 11 is installed is at a high temperature or a relatively low temperature. This measures the output voltage A1 of the common terminal 20 of the resistors R3 and R4 of the bridge B (S3). As described above, since the AH sensor 11 is composed of a heat-sensitive element called a thermistor, the output voltage A1, which is the voltage across the AH sensor, changes linearly so that the voltage level decreases as the temperature increases.

The above output voltage A1 is A/D converted and the interface 2
At the same time as it is introduced into the microcomputer 22 via 1, it is compared with the numerical value 3 previously stored in the ROM 22b (S4) If L, A1>3, it is determined that this is a low temperature state where dew condensation is likely to occur, and it is still Al>3. If not, it is assumed that there is no condensation in the heating chamber and the normal heating sequence starts AH
Set the initial value reading time TQ of the sensor 11 to 16 seconds (S
5) Do. In the case of AI>3, the output voltage A2 of the AH sensor 11 after time T1 from the start of heating is set to A2Q'
l) and the output voltage A2 of the AH sensor 11 after time T2 from the start of heating as A2 (T2).
Store these values in c (56) and (S7) L. Calculate these values as α = A2 (T2) A2 (71) (S8) L, and if the value of α is α≧1, the humidity at which dew condensation occurs. If α<1, it is determined that there is condensation inside the heating chamber 7, and the initial value reading time To is set to 32 seconds (S9), which is longer than the normal reading time. In this way, by calculating the value of α, the state of dew condensation in the heating chamber is determined, and the reading time TQ is selected and set.
Confirm the passage of this cleaning time (S10). When the predetermined cleaning time has elapsed, the rHighJ signal output from the microcomputer 22 via the interface 21 causes the transistor 23 to energize the ONL relay 24. Commercial power is supplied to the magnet, Netron 8, and microwave oscillation is started (S I").The time it takes for the water vapor condensed by microwave heating to exhaust to the outside of the heating chamber and reach the safe range. is the above TQ=
32 seconds, and the output A2 of the AH sensor shown by ■ in FIG. 9 is stored in the RAM 22c as A20 (S1
2) Do. In this way, by slightly delaying the reading time of the initial value of the AH sensor 11, the stable state of the output of the AH sensor 11 is confirmed, and furthermore, the heated state of the food by microwave heating is determined at the predetermined detection level of the AH sensor 11 ( K''A20 or A20+ΔH) and determines (S13) that when they match, the finishing is completed, and the rLowJ signal output from the microcomputer 22 via the interface 21 causes the transistor 23
At 0FFI, the power supply to the IJ relay 4 is stopped, thereby stopping the operation of the magnetron 8 and ending the microwave heating (515).

In the above embodiment, when the dew condensation occurs, the A
The output value of the H sensor in the stable region is stored in the microcomputer, but before moving on to heat, the heating chamber is heated for several minutes with a heater to evaporate the condensation, and then microwave heating is started. The optimum finish may be obtained by modifying the value of the predetermined detection level (K-A2° or A20+ΔH) of the AH sensor.

<Effects> As explained above, the present invention includes a detection means for detecting the rate of change in the output of the absolute humidity sensor, and a time period for storing the initial value of the absolute humidity sensor according to the output of the detection means. Since it is equipped with an initial value reading time setting means that can be selectively set, even if there is dew condensation inside the heating chamber, the 4M effect on the output level of the absolute humidity sensor caused by condensed water vapor, that is, the 4M effect on heated food, can be avoided. Since it is possible to prevent an unheated state in which the food is finished sooner than a predetermined time, it is possible to easily obtain an optimal finish according to the cooking menu.

[Brief explanation of the drawing]

Figure 1 is a front view of the microwave oven, Figure 2 is its schematic cross-sectional view, Figure 3 is an external view of the absolute humidity sensor, Figure 4 is a detailed cross-sectional view of Figure 3, and Figure 5 is the absolute humidity measurement circuit. Figure 6 is a general output characteristic diagram of an absolute humidity sensor, Figure 7 is an output characteristic diagram of an absolute humidity sensor showing dew condensation status, and Figure 8 is a typical output characteristic diagram of an absolute humidity sensor.
Figure 9 is a circuit diagram of the main parts of a microwave oven showing an embodiment of the present invention, Figure 9 is a characteristic diagram explaining the operation of the absolute humidity sensor shown in Figure 8 above, and Figure 10 is a flow chart showing an overview of the operation of the present invention. It is. 2. Operation panel 3. Menu selection key, 4.
Heating start key, 7... heating chamber, 8 magnetron,
9.Fan, II ・Absolute humidity 7-12] ・Interface, 22 ・Microcomputer, 28
fan motor. Agent Patent attorney Aihiko Fuku (2 others) Figure 1 Figure 2 Figure 3 Blue l /-211-11 = 4 Gu No. 71'& 1 Figure I exhortation sheet t taV fight 1

Claims (1)

[Claims] 1 Equipped with a detection means for detecting the rate of change in the output of the absolute humidity sensor, and an initial value reading time setting means for selectively setting the time for storing the initial value of the absolute humidity sensor according to the output of the detection means. A microwave oven characterized by wild animals.