JPS6138970B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cooking device for heating food, such as a microwave oven that performs high-frequency dielectric heating, an oven for making bread or cakes, and a grill for browning.

For example, in a microwave oven, food is cooked in a heating chamber by high frequency waves from a magnetron, and a detection element detects the infrared rays emitted from the food as it is heated. The heating temperature is controlled. In such a cooking appliance, when an abnormality occurs, such as when water vapor, volatile oil, foreign matter, etc. adhere to the light-receiving surface of the detection element, or when the detection element deteriorates, the output from the detection element changes. Accordingly, the detection element will erroneously detect the heating temperature of the food to be cooked. Therefore, the food to be cooked was either underheated or overheated.

The purpose of the present invention is to solve the above-mentioned technical problems,
To provide a cooking device which can eliminate underheating or overheating of food to be cooked and can also check abnormality of a detection element.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a simplified perspective view of one embodiment of the invention, and FIG. 2 is a longitudinal sectional view thereof. A turntable 4 that rotates around a vertical axis 3 is provided in a heating chamber 2 of a body 1 such as a microwave oven. This turntable 4 is rotationally driven by a motor 5. A food to be cooked 6 is placed on the turntable 4. The food to be cooked 6 is dielectrically heated by high frequency power from the magnetron 7. A detection element 8 is provided within the body 1 above the heating chamber 2 and on the vertical axis 3 . This detection element 8 detects infrared rays generated when the food to be cooked 6 is heated.

An insertion hole 10 is provided on the vertical axis 3 of the ceiling 9 of the heating chamber 2 . Solenoid 1 is on the ceiling 9.
1, a movable piece 14 is provided which is movable in the directions of arrows 12 and 13. By pressing and operating the heating switch 38 provided on the operation panel 15 provided on the front of the machine body 1, the food to be cooked 6 is heated, and the solenoid 11 is energized and the movable piece 1 is heated.
4 moves in the direction of arrow 13 to open the insertion hole 10.
When the food to be cooked 6 is heated and cooked, the heating is stopped and the solenoid 11 is demagnetized, and the movable piece 14 moves in the direction of arrow 12 to close the insertion hole 10.
The monitor heater 17 provided on the movable piece 14 is activated by pressing the inspection switch 16 for checking abnormality of the detection element 8 when not cooking.
is located on the vertical axis 3 and is energized.

Vertical axis 3 of plate 18 provided above ceiling 9
An insertion hole 19 is provided on the top. On board 18,
Motor 20 is fixed. A space 21 that is the shaft of the motor 20 and is made up of the ceiling 9, the plate 18, and the fuselage 1.
A shielding plate 22 is fixed inside. Shielding plate 22
has, for example, three blades, and intermittently transmits infrared rays to the detection element 8 through the insertion hole 19 through the gap between the blades. A constant flow of air is introduced into the space 21 by a fan 24 driven by a motor 23. Therefore, space 2
1 can be kept constant. Moreover, the air in the space 21 is forced out into the heating chamber 2. Therefore, gas such as water vapor from the heating chamber 2 is restricted from entering the space 21. In addition, the mesh made of punched metal provided on the door 25 for opening and closing the heating chamber 2 is prevented from being clogged with gas generated from the food to be cooked, and the air can be penetrated from the outside through the mesh. The inside of the heating chamber 2 can be visually observed. Moreover, the hot air in the heating chamber 2 can be circulated to make the temperature uniform.

FIG. 3 is a specific electrical circuit diagram of one embodiment of the present invention. Power via the plug 31 is applied via lines 32, 33 to the primary winding of the transformer 34 and to the magnetron 7. line 32
A series circuit consisting of motor 20, solenoid 11, and motor 23 and motor 5 are connected between line 33 and line 33. When power is supplied through the plug 31, the motor 20 rotates,
Accordingly, the shielding plate 22 is rotationally driven. line 32
When the heating switch 38 provided on the operation plate 15 is pressed, the solenoid 11,
The motors 23, 5 and the transformer 34 are energized, the relay 40 having the relay coil 39 is energized, the relay switch 41 provided in the middle of the line 32 is made conductive, and the magnetron 7 is energized. When the solenoid 11 is energized, the movable piece 14 moves in the direction of arrow 13 and opens the insertion hole 10. The heating switch 38 and relay switch 41 of the relay 40 self-maintain a conductive state when the relay coil 39 is energized, and self-maintain a cut-off state when the relay coil 39 is demagnetized. Relay 36 has a relay coil 42. When the relay coil 42 is excited, the relay switch 37 self-maintains a conductive state, and the relay switch 4 provided on the line 32 between the relay switch 41 and the magnetron 7
3 self-maintains the cut-off state. Relay coil 42
When is demagnetized, the relay switch 37 self-maintains the cut-off state, and the relay switch 43 self-maintains the conductive state.

A diode 44 is connected to the secondary winding of the transformer 34.
A rectifier circuit 48 consisting of .about.47 is connected. Power from the transformer 34 is rectified by a rectifier circuit 48 and smoothed by a capacitor 49. capacitor 4
9 is connected in parallel with a field effect transistor (Field
Effect Transistor (hereinafter abbreviated as FET) 50
A series circuit consisting of a resistor 51 and a resistor 51 is connected.
A detection element 8 is connected between the gate of FET50 and ground.
is connected. In response to the infrared radiation from the food to be cooked 6, the detection element 8 derives an output. Detection element 8
The output from is amplified by FET50,
The signal is applied to the detection circuit 52 from the source of the FET 50. The detection circuit 52 amplifies the output from the source of the FET 50 to excite the relay coil 39, and also detects a predetermined heating temperature setting value and the FET 50.
It has a function of comparing the output from the source and demagnetizing the relay coil 39 when the food to be cooked 6 reaches a predetermined heating temperature setting value.

If the detection element 8 is normal, the heating switch 3
When 8 is pressed, the relay switch 41 becomes conductive and the magnetron 7 is energized, and the detection element 8 detects a predetermined set temperature. Therefore, the object to be heated 6 is properly cooked.

Although air is blown from the space 21 and forced into the heating chamber 2 as described above, the air pressure inside the heating chamber 2 increases due to water vapor from the food to be cooked 6, so the cooking process is repeated several times. When heating is performed, water vapor and the like within the heating chamber 2 will reach the space 21. Therefore, water vapor or the like may adhere to the light-receiving surface of the detection element 8. Therefore, the output from the detection element 8 will decrease or increase. This causes the food to be cooked 6 to be overheated or underheated, and therefore it is necessary to check the detection element 8 for abnormality.

The power from the plug 31 is connected to the line 53,
54 to the primary winding of a transformer 55. A check switch 16 is provided in the middle of the line 53. A rectifier circuit 60 consisting of diodes 56 to 59 is connected to the secondary winding of the transformer 55. Power from the transformer 55 is rectified by a rectifier circuit 60 and smoothed by a capacitor 61. In parallel with the capacitor 61 is a series circuit consisting of timers 62, 63, a monitor heater 17, and a tire switch 64 controlled by the timer 62, and an FET 65.
and a series circuit consisting of resistor 66, resistor 67,6
8, a series circuit consisting of relay coil 42 and transistor 69, and a series circuit consisting of lamp 35 and relay switch 37 of relay 36 provided on operation panel 15 are connected. A timer switch 70 controlled by the timer 63 from the detection element 8 is connected to the gate of the FET 65.
The output via is given. The source of FET 65 is connected to one input of relatively 71. The connection point between resistor 67 and resistor 68 is connected to the other input of comparator 71. The output of comparator 71 is applied to the base of transistor 69.

If the check switch 16 is pressed while the food is not being cooked, the monitor heater 17 is energized. The monitor heater 17 has a small thermal time constant.
The rise time T1 from when the power is applied until the temperature reaches a certain temperature, for example, 50° C., is short, and the power consumption is low. The timer switch 64 is turned on for a time T2 from when the inspection switch 16 is pressed until it is shut off under the control of the timer 62. The timer switch 65 is controlled by the timer 63 and becomes conductive after a delay time T3 (T2>T3>T1) after the inspection switch 16 is pressed. Therefore, the detection element 8 detects and outputs the temperature of 50° C. of the monitor heater 17.

The voltage division ratio by the resistors 67 and 68 is determined based on, for example, an unacceptable abnormal temperature of 40°C. When the detection element 8 is normal, the detection element 8 derives an output corresponding to the temperature of the monitor heater 17 of 50°C. The voltage applied to one input of the comparator 71 is a voltage corresponding to 50°C, and the voltage applied to one input of the comparator 71
The voltage applied to the other input of 1 is a voltage corresponding to 40°C. Comparator 71 compares the voltages applied to both inputs and derives a low level signal. Accordingly, transistor 69 remains cut off. Therefore, relay coil 42 remains demagnetized and relay switch 43 remains conductive.
Therefore, cooking can be performed while confirming that there is no abnormality in the detection element 8.

In the case of an abnormality such as water vapor adhering to the detection element 8, the detection element 8 is heated to 50°C by the monitor heater 17.
Receives and outputs the temperature as less than 40℃. The voltage applied to one input of the comparator 71 is
The voltage applied to the other input of the comparator 71 is a voltage corresponding to 40°C. Comparator 71 compares the voltages applied to both inputs and derives a high level signal. In response, transistor 69 becomes conductive and relay coil 42 is excited. Therefore, the relay switch 37 becomes conductive, and the lamp 35 lights up to notify that the detection element 8 is abnormal. Further, the relay switch 43 is shut off so that cooking cannot be performed.

The reference level for detecting an abnormality in the detection element 8 may be changed by changing the voltage division ratio by the resistors 67 and 68.

As described above, according to the present invention, it is possible to detect whether the detection element is working normally or not, and the food to be cooked can be appropriately cooked.

[Brief explanation of the drawing]

FIG. 1 is a simplified overall perspective view of one embodiment of the present invention, FIG. 2 is a sectional view thereof, and FIG. 3 is a specific electric circuit diagram thereof. 6...To be cooked, 7...Magnetron, 8...
Detection element, 11... Solenoid, 14... Moving piece, 16... Inspection switch, 17... Monitor heater, 35... Lamp, 36... Relay, 37, 4
3... Relay switch, 38... Heating switch,
42...Relay coil, 65...FET, 66~
68...Resistor, 71...Comparator.

Claims (1)

[Claims] 1. It has a detection element that detects infrared rays emitted from the food to be cooked and derives an output, and the output from the detection element corresponds to the temperature at which the cooking of the food is completed. In the cooker configured to stop heating when the temperature is exceeded, the monitor heater is movable and faces the detection position of the detection element and generates heat at a predetermined temperature; and the detection element detects the temperature of the monitor heater. an abnormality detection means for detecting an abnormality in the detection element by comparing the output from the detection element with a predetermined setting value corresponding to an abnormal state of the detection element; 1. A cooking appliance characterized by comprising a means for notifying the abnormality and disabling cooking by heating when the abnormality occurs.