JPS6127661B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating device having a control mechanism for detecting burnt marks on a heated object and automatically heating the object appropriately.

In heating devices such as electric ovens, gas ovens (or grills), microwave ovens, etc., which supply hot air or infrared rays from an electric heater or gas burner to heated objects stored in a heating chamber, Conventionally, the degree of browning of objects is controlled by using a timer and allowing the user to set the heating time. However, since the heating time required to obtain the desired browned appearance varies depending on the amount and moisture content of the material to be heated, the type of composition, and even the shape, considerable skill is required to set the heating time. Inappropriate settings often result in over-heating or under-heating the object to be heated.

For this reason, even if a timer is provided, the user must constantly monitor the degree of burntness of the object to be heated, which has the drawback of being inconvenient to use.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a heating device that automatically controls the degree of burntness of a heated object.

In order to achieve the above object, the present invention is equipped with a lamp that irradiates visible light onto an object to be heated in a heating chamber, and a photosensor (CdS) that receives reflected light from the surface of the object to be heated. Then, the burnt condition is detected, and heating by an electric heater, gas burner, etc. is stopped when a proper burnt condition occurs.

The present invention will be specifically explained below using the drawings.
FIG. 1 is a cross-sectional view of a hot air circulation type microwave oven, which is an embodiment of the present invention.

In the figure, 1 is a heating chamber, 2 is a turntable made of heat-resistant high frequency low loss material, 3 is an object to be heated,
4 is a door, 5 and 5' are electric heaters, 6 is a high-frequency oscillation tube, 7 is a waveguide, 8 is a motor for the turntable 2, 9 is a fan, 10 is a lamp, 11 is a condenser, 12 is a mirror , 13 is a lens for adjusting the light receiving range;
14 is a light sensor (CdS), 15 is a control device, 16
1 is a power supply device, 17 and 17' are ventilation ports, 18 is a suction port, and 19 is a punch hole. In addition, light receiving component 1
1. The mirror 12 and lens 13 are made of heat-resistant materials.

Now, when the door 4 is opened and the heated object 3 is placed on the turntable 2, the door 4 is closed and the power supply device 16 is driven, the lamp 10 is lit and illuminates the heated object 3. The reflected light is collected by the condensing part 11 and the mirror 1.
2. Sent to the optical sensor 14 via the lens 13,
The control device 15 stores the illuminance from the object 3 to be heated. On the other hand, the electric heaters 5, 5' and the fan 9 start operating, and hot air flows into the heating chamber 1 from the ventilation ports 17, 17'.
sent inside. Note that the hot air circulates through the suction port 18. The object to be heated 3 is heated by this hot air. At the same time, the motor 8 for the turntable 2 operates to further reduce uneven heating of the object to be heated 3. Eventually, when the surface of the object to be heated 3 begins to burn, the illuminance detected by the optical sensor (CdS) 14 decreases. When this illuminance reaches a preset value, the control device 15 sends a signal to the power supply device 16.
The power supply device 16 receives this signal and turns on the electric heater 5,
5' and the fan 9 are stopped, and the high frequency oscillation tube 6 is driven. High frequency power generated by the high frequency oscillation tube 6 is supplied into the heating chamber 1 via the waveguide 7. The object to be heated 3 is heated by this high frequency power. Further, when a preset time has elapsed, the power supply device 16 stops the operation of the high frequency oscillation tube 6, motor 8, and lamp 10.
Therefore, heating of the object to be heated 3 is completed. In addition,
The condensing section 11 needs to have dimensions that prevent leakage of high-frequency power. Further, the condensing section 11 is provided to detect the burnt edges of the object to be heated 3 while preventing the hot air from going toward the optical sensor (CdS) 14 . Condenser 11, mirror 12, lens 1
The reason for providing the optical device consisting of 3 is to eliminate the influence of the temperature characteristics of the optical sensor (CdS) 14. Furthermore, better performance can be obtained by cooling the optical sensor (CdS) with wind. In addition, in the figure, light is indicated by a dotted line, and hot air is indicated by a chain line.

Next, the signal detected by the optical sensor (CdS) is
The microwave oven shown in the figure will be described. Second
The figure shows the change in resistance value of the optical sensor (CdS) with respect to heating time. As shown by the solid line A, the resistance value R ₁ at the start of heating (t ₁ ≒ 0) burns as the object to be heated 3 reaches time t ₃ .
The illuminance on the surface of the object to be heated 3 decreases, and as a result, the resistance value of the optical sensor (CdS) increases to _R2 . Therefore, it is possible to detect the degree of burning based on the resistance value of the optical sensor (CdS). Further, a case where the object to be heated 3 is whiter than that shown in solid line A is shown in solid line B. As can be understood from the figure, the whiter the object 3 to be heated, the lower the resistance value at the heating start time. For this reason, if the setting value of the control device 15 is simply set to a constant absolute value, heating with hot air may not be performed depending on the color of the object 3 to be heated. For example, if the set value is set to the resistance value R _p , heating with hot air will stop at time t ₂ in the case of the object to be heated shown by the solid line B, but in the case of the object to be heated shown by the solid line A. does not heat with hot air. This is because, as shown by the arrow in the figure, the resistance value R ₁ at the start of heating in the case of the object to be heated indicated by the solid line A is higher than the set value R _p . For this reason, as described in FIG. 1, control is performed using the increase value from the detection signal (resistance value) of the optical sensor (CdS) at the start of heating. Furthermore, since the whiter the object to be heated, the greater the slope (rate of change) of the resistance value, correction is required. This point will be explained in detail later.

Next, FIG. 3 shows the resistance value of the optical sensor (CdS) with respect to heating time, and the light receiving range of the optical sensor will be described. In the figure, a solid line C indicates a case where the light receiving range of the optical sensor is the range of the turntable 2, and a solid line D indicates a case where the light receiving range of the optical sensor is set to be larger than that, and the same object to be heated 3 is used. As can be seen from the figure, the solid line C is more sensitive to burnt objects to be heated (has a larger slope).

The main reason for this is that the light from the lamp 10 is reflected on the wall of the heating chamber 1, and the reflected light is detected by the optical sensor (CdS) 14 (the same applies to the light that enters from the window window installed in the door 4). This is because changes in the reflected light from the surface of the object to be heated 3 have little effect on the overall illuminance. Therefore, when the light receiving range is wide, the sensitivity deteriorates. However, if the light receiving range is narrow, on the other hand, the degree of burntness of the object to be heated 3 will be detected partially, and errors will occur due to uneven heating of the object and the position. Therefore, there is a light receiving range, but the optimum range is the range of the turntable 2 in consideration of the case where a load is placed on the entire turntable 2. In addition,
In FIG. 1, the turntable 2 is used, so the scope is referred to as the range of the turntable 2, but there are also cases where a square plate or the like is placed on a shelf, and in that case, the lowermost saucer installation range is effective. Further, the approximate dimensions of the ceiling are effective for the light condensing section 11 and the lamp 10.
This is because it is possible to receive reflected light from approximately the entire surface (surface) of the object to be heated 3, and the extent of burntness can be detected as a whole. Note that when the lamp 10 is used to view the object to be heated from the viewfinder (door 4),
The best location is the door 4 side from the center of the ceiling.

It is obvious that the object to be heated 3 can be easily seen if the front side (door side) of the object to be heated is bright.

Next, a fourth embodiment of the circuit configuration of the control device 15 will be described.
As shown in the figure. In FIG. 4, reference numeral 14 is an optical sensor that detects the illuminance on the surface of the object to be heated 3, and is CdS as described above. 19 is a DC power supply, 20 is a switch, 22 is a Zener diode, 24 is a non-inverting DC amplifier, 26 is a volume, 27, 35, 3
7 is a diode, 28, 38 is a capacitor, 29
is a comparator, 30 is a positive input terminal of the comparator 29, 31 is a negative input terminal of the comparator 29, 32 is a relay, 33 is a primary coil of the relay 32, 34' is a secondary contact of the relay 32, 21,2
3, 25, and 36 are resistors. When the switch 20 is turned on, the resistor 21 and Zener diode 22
A constant voltage circuit consisting of a CdS 14 and a resistor 2 shifts the voltage supplied from a DC power supply 19.
A constant voltage V _z is supplied to the series circuit of 3. CdS 14 and resistor 23 divide this constant voltage V _z and apply voltage V _T to the input side of non-inverting DC amplifier 24 . Since this voltage V _T changes depending on the degree of light reception by the CdS 14, it is an electrical signal that detects the degree of burning of the object to be heated 3, and when the illuminance on the surface of the object to be heated 3 decreases, the resistance value of the CdS 14 increases. to drop. The non-inverting amplifier 24 has a voltage V _T
is amplified (in positive phase) and outputs a voltage V _I (hereinafter referred to as a dark spot detection voltage). The dark spot detection voltage V _I is applied to the positive input terminal 30 of the comparator 29 via a low-pass filter consisting of a resistor 36 and a capacitor 38 (the voltage V _I ' applied to this input terminal 30 is the same as the voltage V _I) . , called the dark spot detection voltage). On the other hand, the dark spot detection voltage V _I is resistor 2
5 and a volume 26 in series. This divided voltage V _S is input to a capacitor memory circuit consisting of a diode 27 and a capacitor 28 . Capacitor 28 stores approximately the maximum value of voltage V _s and provides memory voltage V _M to negative input terminal 31 of comparator 29 . The comparator 29 compares the input voltages V _I ' and V _M , and outputs a high level output voltage when V _I '> V _M .
Further, when V _I '<V _M , a low level output voltage is supplied to the primary coil 33 of the relay 32. relay 3
2 turns on the secondary contact 34 connected to the power supply 16 when the output voltage of the comparator 29 is at a high level. When the secondary contact 34 is turned on, the power supply device 16 heats the heated object 3 with hot air, as described in FIG. The device is configured to perform heating. Note that the diode 35 is connected to the capacitor 28 and also to the diode 3.
Reference numeral 7 is for discharging the capacitor 38, and when the switch 20 is turned from on to off, the capacitors 28 and 38 are discharged with a time constant smaller than the time constant during charging.

In the above circuit, the object to be heated 3 is placed on the saucer 2, the door 4 is closed, and the switch 20 is turned on.
At this point, the capacitors 38 and 28 are short-circuited, and the memory voltage V _R is set lower than the burnt detection voltage V _I ' by the resistor 25 and the volume 26, so the comparator 29 is connected to the relay 32. A high level voltage is supplied to the primary coil 33, and the secondary contact 34 is turned on. Therefore, the power supply device 16 operates, the lamp 10 lights up, and the fan 9, electric heaters 5, 5', and turntable motor 8 start operating. At this time,
The resistance value of the CdS 14 decreases from a high resistance, and the dark spot detection voltage V _I increases. This increase reaches its peak in about 10 seconds at the latest. Eventually, when the object to be heated 3 begins to burn, the illuminance on the surface of the object to be heated 3 begins to decrease, and the resistance value of the CdS 14 gradually increases. Therefore, the dark spot detection voltage V _I gradually decreases. As a result, the voltage V _s similarly reaches a peak and then decreases, so that the diode 27 is cut off and the memory voltage V _M is stored in the capacitor 28 . When the burnt state further progresses and the burnt detection voltage V _I becomes smaller than the memo voltage V _M , the comparator 29 changes the high level voltage supplied to the primary coil 33 of the relay 32 to the low level voltage. invert it.

Accordingly, the secondary contact 34 is turned off, so heating by hot air is switched to heating by high frequency power, and heating ends when a preset time has elapsed. Furthermore, driving of the lamp 10 and motor 8 is also stopped. In addition, Fig. 5 shows the
The characteristics of the dark spot detection voltage V _I corresponding to the resistance value characteristics of CdS 14 are shown. As shown by the solid line A, the voltage V ₃ at the initial stage of heating (starting time t≈0) drops to voltage V ₄ after the elapse of time t ₃ . In addition, in the case of the white heated object 3 (solid line B), the voltage at the initial stage of heating is higher and the slope (rate of change) of the voltage is larger than in the case of solid line A. Therefore, in the present invention, a resistor 25 and a barium 26 are used for correction. In other words, if the resistance value of the resistor 25 is R, the resistance value of the volume 26 is V _R , and the range of change in the burnt detection voltage V _I at the initial stage of heating is △V _I , then the range of change in the memory voltage _VM is △V _M Since △V _M =V _R /R+V _R ×△V _I , correction can be applied.

FIG. 6 shows the characteristics of this correction. As shown in the figure, the variation width ΔV _M of the memory voltage V _M becomes smaller than the variation width ΔV I of the burnt eye detection voltage (initial stage of heating) V _I , and the higher the _{V I is} , the larger the slope becomes.

Next, the color of the saucer 2 will be described as it affects the dark spot detection control. Similar to what was stated in FIG. 3 when the color of the saucer 2 is white, the sensitivity decreases when the object to be heated 3 is small. Furthermore, in the circuit configuration shown in FIG. 4, the dynamic range of the amplifier 24 must be widened, which increases cost. Furthermore, from the viewpoint of the lifespan of the optical sensor (CdS), it is not preferable to provide excessive illuminance, so the color of the saucer 2 is preferably black.

As described above, the present invention makes it possible to automatically control darkening, which conventionally relied on the sense of sight.
Usability can be improved.

In this embodiment, a case has been described in which a light source (lamp) is provided near the outside of the heating chamber, but the present invention is also effective even if the light source (lamp) is provided in a part of the heating chamber.

Further, in this embodiment, a case has been described in which there is only one light source and one optical sensor, but the present invention is still effective even if there are a plurality of light sources and optical sensors.

Furthermore, although the optical sensor (CdS) is used in this embodiment, the present invention is also effective even if other optical optical sensors such as photodiodes are used.

Furthermore, in this embodiment, a case has been described in which the heating form is changed when the signal from the optical sensor reaches a preset value, but the present invention is also effective in cases where heating is stopped or the degree of heating is changed. There is.

[Brief explanation of the drawing]

FIG. 1 shows an example of the configuration of the heating device of the present invention. FIG. 2 shows the resistance change of the optical sensor (CdS) as the burnt grain progresses on the object to be heated, and FIG. 3 shows the optical sensor (CdS). Figure 4 shows an example of the circuit configuration of the control device of the present invention, and Figure 5 shows changes in the dark eye detection voltage V _I in Figure 4. 6 is a diagram showing the characteristics of the dark spot detection voltage V _I and the memory voltage V _M at the initial stage of heating in FIG. 4. In the figure, 1... heating chamber, 2... saucer, 3... object to be heated,
5, 5'...Electric heater, 6...High frequency oscillation tube,
9...Fan, 10...Lamp, 11...Concentrator, 12...Mirror, 13...Lens, 14...Photo sensor (CdS), 15...Control device, 16...Power supply device, 19... ...DC power supply, 20...Switch, 2
2... Zener diode, 24... Non-inverting amplifier, 25... Resistor.

Claims (1)

[Claims] 1. A heating device having a heating means capable of heating an object to be heated stored in a heating chamber until browned, comprising: a light source means for irradiating visible light onto the surface of the object to be heated in the heating chamber; optical sensor means for detecting the illuminance of the reflected light from the surface;
a calculating means for outputting a calculated value based on the output value of the optical sensor means; a storing means for storing the calculated value outputted by the calculating means at a specific time; and an output value of the optical sensor means and the storing means. 1. A heat-adding device for a burnt eye detection control mechanism, characterized in that it has a comparison means for comparing stored values of the , and a control means for controlling the heating operation of the heating means in response to the output of the comparison means.