JPS6131515Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a microwave oven that performs hot air heating in addition to microwave heating.

A microwave oven according to an embodiment of the present invention will be described in detail below. 1st
In the figure, 1 is the main body of the microwave oven, 2 is a heating chamber disposed within the main body, 3 is food placed in the heating chamber, 4 is a magnetron that generates microwaves for heating the food, and 5 6 is a blower motor for cooling the magnetron; 6 is a hot air generator that generates hot air for heating the food;
Details of the device are as follows. That is, 7 and 8 are first and second holes bored in the upper wall of the heating chamber 2.
A small hole group, 9 is a hot air duct arranged on the upper wall of the heating chamber 2 over the first and second small hole groups, 10 is a heater provided in the duct, and 11 is a pulley 1.
2, 13 and belt 14 to connect the blower motor 5.
This fan is connected to a hot air fan and is rotated by the driving force of the blower motor 5. The air heated by the heater 10 is discharged into the heating chamber 2 from the second small hole group 8 as hot air.

Figure 2 shows a circuit diagram of the microwave oven, 15
16 is a commercial power supply, 16 is a power fuse, 17 is a door switch that responds to a door (not shown) that opens and closes the opening of the heating chamber 2, and 18 is a timer switch 19.
and a timer motor 20; 21 is a DC high voltage circuit for inputting power from the power source 15 and applying DC voltage to the magnetron 4; this circuit includes a high voltage transformer 22 and a half-wave voltage doubler rectifier circuit 23; It consists of Reference numerals 24 and 25 designate first and second changeover switches for selectively supplying power from the power source 15 to the transformer 22 of the DC high voltage circuit 21 or the heater 10. In the first and second changeover switches, 24a and 25a are first and second common contacts provided on the side of the power source 15, respectively, and 24b and 25b are connected to both ends of the primary winding 22' of the transformer 22, respectively. The first and second microwave contacts 24c and 25c are first and second heater contacts connected to both ends of the heater 10, respectively. 5a and 5b are main and auxiliary windings of the blower motor 5, the main and auxiliary windings are connected in series, and the intermediate tap 5 is connected to the main and auxiliary windings.
c is connected to the first microwave contact 24b side, and one end of the main winding 5a is connected to the second common contact 24b.
5a, and one end of the auxiliary winding 5b is connected to a third heater contact of a third changeover switch, which will be described later. Reference numerals 26 and 27 are a third changeover switch and a blower changeover switch, respectively, which perform two-contact switching. In the third changeover switch 26, 26b and 26c are a third microwave contact and a third heater contact connected to the intermediate tap 5c side and the auxiliary winding 5b side of the blower motor 5, respectively;
26a is a third common contact. On the other hand, in the blower changeover switch 27, 27b and 27c
are the intermediate tap 5c side of the blower motor 5 and the third common contact 2 of the third changeover switch 26, respectively.
Strong and weak contacts 6a are connected, and 27a is a blower common contact connected to the first heater contact 24c side of the first changeover switch 24.

Figure 3 shows the above-mentioned 1st to 3rd changeover switches 24 to 2.
6 is a diagram for explaining the switching operation, in which 28 is the front operation panel of the microwave oven main body 1, 29 is a manual switching operation section provided on the panel, 3
Reference numeral 0 designates a switching lever that is rotatably supported on a support shaft 31, and the operating portion 29 is attached to one end of the lever, and an arc-shaped protrusion 32 is fixed to the lever 30. has been done. The first to third changeover switches 24 to 26 are arranged along the rotating direction of the protrusion. Here, the third
The changeover switch 26 is disposed offset from the first and second changeover switches 24 and 25 by a certain distance in a counterclockwise direction. Note that the first and second changeover switches 24 and 25 are vertically stacked on top of each other in the plane of the paper, so the second changeover switch 25 does not appear in FIG. 3.

The lever 30 is rotated to the position shown by the broken line and the solid line in response to manual operation of the operating section 29. When the lever 30 is rotated to the position indicated by the broken line, the first to third changeover switches 2
4 to 26 are pressed and biased by the protrusion 32, but at this time, the first and second changeover switches 2
4 and 25 are simultaneously pressed and biased, and the first and second common contacts 24a and 25a are simultaneously connected to the first and second common contacts 24a and 25a, respectively.
It is switched and connected to heater contacts 24c and 25c.
Next, the protrusion 32 moves from the positions of the first and second changeover switches 24 and 25 to the third changeover switch 26.
By rotating the switch to the position, the third changeover switch 26 is biased and the third common contact 26a is pressed.
is switched and connected to the third heater contact 26c. The lever operation to the position indicated by the broken line is executed when performing hot air heating. On the other hand, when the lever 30 is rotated to the position indicated by the solid line, the first to third changeover switches 24 to 26 are released from the pressing force applied by the protrusion 32; The switch 26 is released and the third common contact 26
a is switched and connected to the third microwave contact 26b. Next, the first and second changeover switches 24,
25 are simultaneously released and the first and second common contacts 24a and 25a are simultaneously connected to the first and second common contacts 24a and 25a, respectively.
It is switched and connected to microwave contacts 24b and 25b. The lever operation to the solid line position is performed when performing microwave heating.

Incidentally, the blower changeover switch 27 can also be changed manually in the same manner. That is, although not shown, the blower common contact 27a is switched and connected to the strong or weak contacts 27b and 27c in response to the operation of the blower switching operation section. Such a switching connection is applied during hot air heating, and by switching the blower common contact 27a to the strong or weak contacts 27b and 27c during hot air heating, only the main winding 5a of the blower motor 5 is energized, or Main winding 5a and auxiliary winding 5b
The series circuit of is energized. This means that the impedance of the blower motor 5 becomes large or small;
That is, it means that the current value flowing through the blower motor 5 becomes large or small. Therefore, blower common contact 2
By switching 7a to the strong or weak contacts 27b and 27c, the rotation speed of the blower motor 5, that is, the hot air fan 11, increases or decreases, thereby increasing or decreasing the air volume to the heater 10, and the hot air temperature becomes low or high. becomes.

Therefore, to perform hot air heating, when food 3 is placed in heating chamber 2 and the door is closed, door switch 1 is turned on.
7 turns on. Then, the switching operation section 29 is operated to rotate the switching lever 30 to the position indicated by the broken line (FIG. 3). Then, the first and second common contacts 24a of the first and second changeover switches 24 and 25,
25a are the first and second heater contacts 24 at the same time, respectively.
c, 25c, and then the third common contact 26a of the third changeover switch 26 is switched and connected to the third heater contact 26c. Then, depending on whether you want to use low-temperature or high-temperature hot air for heating, operate the blower switching operation section to switch the blower switching switch 27.
The blower common contact 27a is the strong or weak contact 27b,
Switch and connect to 27c. When a predetermined time is set with the timer 18, the timer switch 19 is turned on and the heater 10 is energized, and the main winding 5a of the blower motor 5 or the series circuit of the main winding 5a and the auxiliary winding 5b is energized. Power is applied. Therefore, low-temperature or high-temperature hot air heating is performed for a predetermined period of time.

On the other hand, when performing microwave heating, the switching operation section 29 is operated to rotate the switching lever 30 to the position indicated by the solid line (FIG. 3). in this case,
First, the third common contact 26 of the third changeover switch 26
a is switched and connected to the third microwave contact 26b, and then the first and second changeover switches 24, 2
5, the first and second common contacts 24a, 25a simultaneously connect the first and second microwave contacts 24b, 25, respectively.
b. Therefore, in this case, the magnetron 4 is energized via the DC high voltage circuit 21 to perform microwave heating. Further, the main winding 5a of the blower motor 5 is energized, and the magnetron 4 is cooled by strong wind.

However, in conventional microwave ovens,
As shown in the figure, there is no third changeover switch 26;
The weak contact 27c of the blower changeover switch 27 was connected to one end of the auxiliary winding 5b of the blower motor 5.

In FIGS. 4 and 5, the same parts as in FIGS. 1 to 3 are denoted by the same reference numerals, and their explanations are omitted.

In such a case, the first and second changeover switches 24,
If the installation position of the blower motor 5 is incorrect, the auxiliary winding 5 of the blower motor 5 may
There was a fear that b would be burnt out.

That is, the first and second changeover switches 24,
25, the first and second changeover switches 24 and 25 will not switch at the same time due to the above-mentioned erroneous operation of the changeover lever 30. For example, if the first common contact 24 of the first changeover switch 24
a is connected to the first heater contact 24c, while the second common contact 25a of the second changeover switch 25 may be connected to the second microwave contact 25b. At this time, if the blower common contact 27a is connected to the weak contact 27c in the connection of the blower changeover switch 27, a series circuit is formed between the main winding 5a and the auxiliary winding 5b of the blower motor 5, and the auxiliary winding line 5b and the primary winding 22' of the transformer 22
A series circuit is formed with Here, main winding 5
a, the impedances of the auxiliary winding 5b and the primary winding 22' are R1, R2, and R3, respectively, R1>R2
>The relationship R3 usually holds true. Therefore, the main winding 5
If it is a series circuit of the auxiliary winding 5b and the auxiliary winding 5b, the impedance due to them is R1+R2, and in this case, the current flowing through the auxiliary winding 5b is small, so the auxiliary winding 5b will not burn out. However,
As mentioned above, when a series circuit is formed between the auxiliary winding 5b and the primary winding 22', the impedance due to them is R2+R3, which is smaller than R1+R2, and the auxiliary winding 5b and the primary winding 22' ′
The current flowing to the side increases, and therefore the auxiliary winding 5
b will be burnt out. In this case, the magnetron 4 normally does not oscillate and the impedance R3 on the primary winding 22' side increases, but the impedance R2+R3 is still smaller than R1+R2, and therefore burnout occurs as described above. Further, even during normal operation, the main winding 5a is supplied with power from the power supply 15 as is, but the main winding 5a has a different impedance compared to the auxiliary winding 5b, so it will not burn out.

However, according to the present invention, the third changeover switch 26 is provided as described above, and the third changeover switch 26 is connected to the first and second changeover switches 24,
25, and the main winding 5 is always switched on before the first and second changeover switches 24 and 25 are switched.
Since the power is supplied from the power source 15 to the auxiliary winding 5b and the primary winding 22 even if the first and second changeover switches 24 and 25 are slightly misaligned, the auxiliary winding 5b and the primary winding 22 A series circuit with ' is not formed, so burning out of the auxiliary winding 5b can be prevented.

As is clear from the above description, according to the present invention, first and second changeover switches are provided at both ends of the magnetron oscillation circuit and the heater circuit in order to switch and supply power from the power source to the magnetron oscillation circuit and the heater circuit. a blower motor consisting of a series circuit of a main winding and an auxiliary winding, for cooling the magnetron and blowing air to the heater;
A third changeover switch is provided for switching and supplying power from the power supply to the main winding or the series circuit, and a contact on the magnetron oscillation circuit side of either the first or second changeover switch is provided. and the heater circuit side contact, the auxiliary winding is connected via the third changeover switch,
When interlocking the third changeover switch with the first and second changeover switches and switching the first and second changeover switches to supply power to the magnetron oscillation circuit, first switch to the series circuit. Since the third selector switch is switched in order to supply power to the main winding, abnormal power is not supplied to the auxiliary winding, thereby preventing burnout of the auxiliary winding, and providing a safe microwave oven. Can be provided.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a microwave oven according to an embodiment of the present invention, Fig. 2 is its circuit diagram, Fig. 3 is a plan view of the same essential parts, Fig. 4 is a circuit diagram of a conventional microwave oven, and Fig. 5 is the same circuit diagram. FIG. 5... Blower motor, 5a... Main winding, 5b...
...Auxiliary winding, 4...Magnetron, 10...Heater, 15...Commercial power supply, 24-26...1st to 3rd changeover switch.

Claims (1)

[Scope of utility model registration request] It consists of a series circuit of a main winding and an auxiliary winding, first and second changeover switches provided at both ends of the magnetron oscillation circuit and the heater circuit in order to switch and supply power from the power supply to the magnetron oscillation circuit or the heater circuit. A blower motor for cooling the magnetron and blowing air to the heater, a third changeover switch for switching and supplying power from the power supply to the main winding or the series circuit, The auxiliary winding is connected between the magnetron oscillation circuit side contact and the heater circuit side contact via the third changeover switch, and the third changeover switch is connected to the first and second changeover switches. When switching the first and second changeover switches to operate in conjunction with the second changeover switch and to supply power to the magnetron oscillation circuit, first change the switch to the series circuit to supply power to the main winding. A microwave oven characterized by switching the third changeover switch.