JPH0216558Y2 - - Google Patents

Description

[Detailed explanation of the idea] (b) Industrial application fields The present invention relates to a microwave oven.

(b) Prior art A microwave oscillator as a first cooking heat source,
For microwave ovens equipped with a heater as a second cooking heat source, in the case of microwave heating, air is blown from an air blower into the heating chamber through its intake port in order to discharge water vapor emitted from the food to the outside of the heating chamber. In the case of heating with a heater, the intake port is closed by a damper to prevent hot air from escaping within the heating chamber. Incidentally, the air blowing when heating the heater is necessary for cooling the outer wall of the heating chamber and the electrical components.

A plunger solenoid device is generally used to open and close the damper that opens and closes the intake port, but the noise generated when the solenoid operates is quite high.

Utility Model Application Publication No. 54-92458 as a prior art,
In order to improve this point, we have disclosed a configuration in which a damper that opens and closes the intake port of the heating chamber is normally closed by the force of a spring, and during microwave heating, the damper is opened by a motor against the spring force. There is.

Although such technology is effective in eliminating the noise caused by conventional plunger solenoid devices, it requires continuous power to the motor during microwave heating, and therefore provides an improvement in terms of power savings. have room to do so.

(c) Problems to be solved by the invention The invention provides a configuration in which the damper that opens and closes the intake port of the heating chamber is operated in combination with a motor and a cam, and there is no need for continuous energization of the motor. It is.

(d) Means for solving the problems The microwave oven of the present invention includes a heating chamber having an air intake, a microwave oscillating section as a first cooking heat source,
A heater as a second cooking heat source, an air blower, a damper that opens and closes the air inlet and causes the air generated by the air blower to flow into the air intake when the air inlet is opened, a cam motor, which is rotationally driven by the cam motor and is at a predetermined rotational position. A cam that places the damper in a fully closed or fully open state, and based on a fully open signal, changes the damper from the fully closed state to a fully open state and stops it in the fully open state, and when the fully open signal disappears, The controller includes a motor drive circuit and a control unit that energizes the cam motor to change the damper from a fully open state to a fully closed state and stop the damper in the fully open state, and the control unit selectively controls the microwave oscillation unit and the heater. In addition to controlling the drive, the blower is also controlled during driving in both directions, and the control section further continuously sends the full open signal during almost the entire drive period of the microwave oscillation section. In addition to giving the full open signal to the motor drive circuit, when the heater is being driven, the full open signal is given to the motor drive circuit only for a period of time approximately equal to the time required for the damper to change from the fully closed state to the fully open state at the beginning of the drive. It is characterized by

(E) Effect According to the present invention, the damper is operated to open and close by a cam rotationally driven by a cam motor, and during microwave heating, the damper changes from a fully closed state to a fully open state, and in the fully open state. The power to the motor is cut off, and when the microwave heating ends, the damper changes from a fully open state to a fully closed state, and in the fully closed state, the power to the motor is cut off. Therefore, heater heating is performed with the damper fully closed. If the microwave heating ends due to an incorrect operation immediately after the microwave heating starts, but before the damper reaches the fully open state, the damper has not yet reached the fully open state, so even though the microwave heating has ended, the microwave heating ends. First, the transition to the fully closed state does not occur, and therefore the damper remains in the half-open state. If heater heating is simply executed after that in such a state, the damper will be heated with the damper half-open, but in this invention, the damper is forcibly brought to the fully open state once in the initial stage of heater heating. , thereafter, the damper automatically shifts to the fully closed state, and therefore heater heating is performed with the damper in the fully closed state.

(F) Embodiment FIG. 3 shows a sectional view of the mechanism of a microwave oven according to an embodiment of the present invention. The heating chamber 2, which is opened and closed by the door 1, includes:
During microwave heating, microwave energy output from the magnetron 3 is supplied, and during heater heating, heat generation energy from the heater 4 is supplied. The magnetron 3 and heater 4, which serve as cooking heat sources, are not driven at the same time. A blower device 7 consisting of a fan 5 and a motor 6 is driven during both microwave heating and heater heating, and during microwave heating, cools the magnetron 3 and the like, and cools the damper 8 and the damper 8 which are in an open state as shown in the figure. Heating chamber intake port 9
Air is blown into the heating chamber 2 through the heating chamber 2. Although not shown, the heating chamber 2 is provided with an exhaust port, so that the heating chamber 2 is forcedly ventilated during microwave heating. When the heater is heating, the intake port 9 is closed by the damper 8, and the air blower 7 cools the outer wall of the heating chamber 2 and the electrical components.

FIG. 1 shows the opening/closing mechanism of the damper 8. L
A mold substrate 11 is fixed to a side wall 10 of the heating chamber 2. A damper 8 is attached to the shaft 1 on the vertical wall 11a of the substrate 11.
A cam 13 and a cam switch CS are mounted on the upper surface of the horizontal wall 11b, and a cam motor 15 for rotationally driving the cam 13 is mounted on the lower surface of the horizontal wall 11b.

The cam 13 has a 180 degree arc shape, and the damper 8
The air inlet 9 of the heating chamber can be fully closed by pressing the button 1, as shown in FIG. A torsion spring (not shown) is wound around the rotation shaft 12 of the damper, and the damper 8 is urged in the opening direction by the force of this spring. Therefore, when the cam 13 rotates half a turn from the state shown in FIG. 1 to the state shown in FIG. 2, the damper 8 is fully opened. In FIG. 2, the dotted line indicates the fully closed position of the damper 8.

The cam 13 rotates clockwise in the figure, and the cam switch CS operates in accordance with the rotation of the cam. That is, the cam switch CS is arranged so that the cam 13 starts biasing it when the damper 8 reaches the fully open state (FIG. 2).

FIG. 4 shows an electric circuit diagram of the microwave oven.
When an instruction for microwave heating or heater heating is given along with the cooking timer time from the keyboard 20, the control unit 21 consisting of a microcomputer controls the second relay switch RB or the third relay switch RC via the interface 22 to set the cooking timer time to the above-mentioned cooking timer time. As a result, the microwave oscillator 3a including the magnetron 3 or the heater 4 is supplied with power from the power lines 23 and 24 during the timer time length. On the other hand, the control section 21 controls the microwave oscillation section 3
When controlling the drive of both the heater 4 and the heater 4, the fourth relay switch RD is energized via the interface 22 for the cooking timer period, so that the blower device 7 closes the power supply line during the timer period. 2
Power is supplied from 3 and 24.

The cam motor 15 is also connected to power lines 23 and 2.
4, and a motor drive circuit 25 is provided to control the energization.
This circuit consists of a cam switch CS and a first relay switch RA. Both of these switches have a normally closed contact NC and a normally open contact NO, and one switch has a normally closed contact NC and the other switch has a normally open contact.
NO and are connected to each other. Cam switch CS
The contact connection state of the first relay switch RA is on the normally open contact NO side when it is energized by the cam 13, and the contact connection state of the first relay switch RA is when it receives the full open signal AO from the control unit 21 via the interface 22. The normally open contact is on the NO side.

As will become clear from the following explanation, when the microwave oven is in a standby state, as shown in FIG. 1, the approximately midpoint of the cam 13 contacts the damper 8, and the cam switch CS is not energized. At this time, the damper 8 is in the fully closed state, and the motor drive circuit 25 is in the fourth connection state.
It will be as shown in the figure.

A case in which microwave heating is performed in the above standby state will be described (see also FIG. 5). Control unit 21
continuously sends the full open signal AO to the motor drive circuit 25 during almost the entire period of microwave heating. Therefore, the first relay switch RA is switched to the normally open contact NO side, and the cam motor 15 is energized. As a result, the cam 13 rotates, and when the cam 13 rotates half a rotation, the damper 8 becomes fully open. At this time, the cam switch CS switches to the NO side of the normally open contact, the power to the cam motor 15 is cut off, and the damper 8 maintains the fully open state from then on. After that, when the microwave heating ends and the full open signal AO disappears,
The first relay switch RA returns to the normally closed contact NC side,
Power supply to the cam motor 15 starts again. As a result, the cam 13 rotates, and when it rotates about 1/4, the damper 8 becomes fully closed, but when the cam 13 rotates another 1/4, the cam switch CS returns to the normally closed contact NC side. The power supply to the cam motor 15 is cut off, and the damper 8 maintains the fully closed state thereafter. The state of the damper 8 at this time is the state shown in FIG. 1, that is, the standby state.

Next, a case where heater heating is executed in the standby state will be described (see also FIG. 6). Control part 2
1 is the time required for the damper 8 to change from a fully closed state to a fully open state at the initial stage of heater drive;
That is, the full open signal AO is applied to the motor drive circuit 25 only for the time required for the cam 13 to rotate half a revolution (usually about 5 milliseconds), preferably slightly longer.
give to Therefore, similarly to the microwave heating described above, the damper 8 becomes fully open, and then returns to the fully closed state once the fully open signal AO disappears.
The damper 8 maintains the fully closed state thereafter. That is, the heater heating is performed with the damper 8 in the fully closed state.

The reason why a fully open signal is given for a predetermined period at the initial stage of heating the heater is as follows. Referring to FIG. 5, as shown by the dotted line in the figure, if the microwave heating ends due to an erroneous operation (for example, pressing the clear key on the keyboard) immediately after the microwave heating starts, but before the damper 8 is fully open. , the damper 8 has not reached the fully open state, so even though the microwave heating has ended and the fully open signal has disappeared, the transition to the fully closed state does not occur, and therefore the damper 8 remains in the half open state. stay.

Now, if the full-open signal at the initial stage of heater heating is not generated, and heater heating is performed in the abnormal standby state with the damper half-open as described above, heater heating will be performed while the damper 8 remains half-open. With such heater heating, the temperature inside the heating chamber drops below the desired value, making it impossible to obtain the desired finished cooking state.

As in this embodiment, when the heater heating is performed with the damper 8 in the half-open standby state, the full-open signal at the initial stage of heater heating brings the damper 8 to the full-open state once, as shown in FIG. When the damper 8 disappears, the damper 8 always returns to the fully closed state, and therefore normal heater heating is performed with the damper fully closed.

In the above embodiment, the driving period of the microwave oscillator and the period of generating the full-open signal AO were the same, but they can be slightly shifted from each other. Furthermore, in the above embodiment, the full open signal AO is generated at the same time as the start of the heater drive, but before and after its generation,
It is also possible to shift it slightly; in short, it is sufficient to generate the full open signal AO at the beginning of heater drive.

(G) Effects of the invention According to the invention, since the damper that opens and closes the intake port of the heating chamber is operated by a combination of a motor and a cam, there is less noise when the damper opens and closes, and there is less noise during heating.
There is no need to continuously energize the motor, so there is a power saving effect.Furthermore, even if the damper is in a standby state with half open, the damper is always fully closed at the beginning of heater heating, so normal heater heating is possible. will be held.

[Brief explanation of drawings]

The figures show an embodiment of the present invention, in which Fig. 1A is a plan view of the damper mechanism, Fig. 1B is a front view of the damper mechanism, Fig. 2 is a plan view of main parts showing the damper fully open state, and Fig. 3 is a microwave oven. 4 is an electric circuit diagram of the microwave oven, and FIGS. 5 to 7 are waveform diagrams. 2... Heating chamber, 3... Magnetron, 4... Heater, 7... Air blower, 8... Damper, 9...
Intake port, 13...cam, CS...cam switch,
15...Cam motor, 25...Motor drive circuit.

Claims (1)

[Scope of utility model registration request] A heating chamber having an air inlet, a microwave oscillating unit as a first cooking heat source, a heater as a second cooking heat source, an air blower, the air inlet is opened and closed, and when the air inlet is opened, the air generated by the air blower is a damper that causes air to flow into the intake port, a cam motor, a cam that is rotationally driven by the cam motor and places the damper in a fully closed or fully open state at a predetermined rotational position, and a cam that changes the damper from a fully closed state to a fully open state based on a fully open signal. a motor drive circuit and a control unit that communicate with the cam motor in order to change the damper in the opposite direction and stop it in the fully open state, and change the damper from the fully open state to the fully closed state and stop it in the fully closed state when the fully open signal disappears; The control unit selectively drives and controls the microwave oscillation unit and the heater, and also controls the blower when both are driven, and the control unit further controls the microwave oscillation unit and the heater. The full-open signal is continuously applied to the motor drive circuit during almost the entire drive period of the oscillation section, and when the heater is driven, at the beginning of the drive,
A microwave oven characterized in that the fully open signal is applied to the motor drive circuit only for a period of time that is approximately the time required for the damper to change from a fully closed state to a fully open state.