JPS626317B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronically controlled cooking appliance, and more specifically to an electronically controlled cooking appliance, such as a so-called oven range, which is equipped with a plurality of electrical heating means driven by an AC power source, and which has a bidirectional thyristor switching function. In an electronically controlled cooking appliance in which the heating means of a lever are energized alternately or sequentially, the electronic control prevents excessive current from flowing in due to simultaneous energization of a plurality of heating means. This is a proposed type cooker.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to drawings showing an embodiment of a so-called microwave oven having a magnetron and a resistance heating element as heating means.

FIG. 1 is an external view of the microwave oven according to the present invention, in which a door latch 17 is provided on the inner side of the door 14 provided to open and close the opening of the cooking chamber 12.
A door switch knob 18 is provided in a protruding manner, and when the door is closed, the door switch knob 18 comes into contact with the door switch to turn on its normally open contacts 451 and 452 (see FIG. 2). A resistance heating element such as an infrared lamp heater or a sheathed heater (hereinafter referred to as a heater 50, see FIG. 2) is installed on the upper surface of the cooking chamber 12, and a microwave heater (described later) is installed in the casing on the side of the cooking chamber. A generator 22, a microprocessor 41, etc. are housed therein, and a control panel 13 on the surface thereof has a display segment as shown in FIG. 3, and a display section 15 for displaying information such as time.
An operating section 16 as shown in FIG. 4 together with a display section 15 is provided.

FIG. 2 shows the electric circuit of the product of the present invention, in which numeral 41 indicates a microprocessor that controls the microwave generator 22, which includes a magnetron 27, etc., and the resistive heating element 50, and 40 indicates a DC power supply. It shows the part. The terminals 25 and 26 are terminals connected to a commercial power source for supplying power to the microwave generator 22, the heater 50, and the DC power source 40, and
The case of this microwave oven is grounded using a terminal 11.

First, this electric circuit will be explained from the DC power supply section 40. The terminals 25 and 26 are connected to the power transformer 33.
DC voltages V C , -V D and AC voltage Vf are connected to the primary winding of the main winding, and the secondary winding with appropriate taps supplies DC voltages V _C , -V _D and AC voltage Vf to the required circuit parts as shown in the figure.
and 60Hz (or
50Hz) sine wave signal TB can be extracted.

The microwave generator 22 consists of a magnetron 27, a high voltage transformer 28, etc.
While the contact 451 of the door switch is closed, the excitation coil RLC of the electromagnetic relay RL is energized and its normally closed contact _R2 is opened, thereby creating a short circuit related to the gate of the bidirectional thyristor 24. This bidirectional thyristor 2
This is performed when a gate signal is applied to 4.

On the other hand, when power is supplied to the heater 50, the contact 451 is closed, while the excitation coil RLC is energized and excited, and its normally closed contact _R1 is opened, thereby opening a short circuit related to the gate of the bidirectional thyristor 54. This is done when a trigger signal is applied to the bidirectional thyristor 54.

Note that the lamp 32 in the cooking chamber 12 is lit by the contacts that are reciprocally closed when the contacts R ₁ or R ₂ are opened, and only the filament of the magnetron 27 is energized.

In this way, the magnetron 27 serving as the heating means and the heater 50 are turned on and off directly by the bidirectional thyristors 24 and 54, respectively.
These on/off operations are controlled by the microprocessor 41, transistors Q ₁ , Q ₂ , Q ₃ , and photocoupler 3.
This is performed by a control section consisting of 7, 57, etc. That is, when a high level signal OM is applied from the microprocessor 41 to the transistor _Q1 , the excitation coil RLC is energized and the normally closed contacts _R1 and _R2 are opened. On the other hand, the high level signal OP (or OH) from the microprocessor 41
is applied to the transistor Q ₂ (or Q ₃ ), the light emitting element of the photocoupler 37 (or 57) emits light,
A gate signal is given to the bidirectional thyristor 24 (or 54) by the light-receiving element that receives this light, thereby energizing the magnetron 27 (or heater 50). For example, the signal OM maintains a high level as long as there is time left on the timer, but OP or OH repeats high and low alone or alternately, thereby increasing the average output of the magnetron 27 or heater 50. It is possible to apply both average outputs simultaneously without adjusting or increasing the overall input current.

Next, the microprocessor 41 has a control unit 60, an arithmetic unit 61, an accumulator 62, a RAM (random access memory) 63, and a RAM buffer 6, as shown in FIG.
4. It is a so-called one-chip microcomputer in which an input/output interface 65, etc. are mounted on one chip, and in this embodiment, a microprocessor μPD553 manufactured by NEC Corporation is used. Data transmission and reception between the above sections is controlled by a control unit 60 and performed via a data bus 66. This microprocessor 41 further includes a basic clock signal generator 67, an interrupt control unit 68, and a reset unit 69, and the basic clock signal generator 67 has terminals OSC ₁ and OSC ₂ as shown in FIG. By externally connecting a coil and capacitor for determining circuit constants, the oscillation frequency is 400K.
Hz. Interrupt control unit 68
As shown in Fig. 2, the time reference signal TB', which is a 60Hz pulse signal obtained by inputting the sine wave signal TB to the waveform shaping/phase shifting circuit 44, is received via the interrupt terminal INT, and this is input. Performs interrupt processing for timekeeping operations when necessary. The reset unit 69 is connected to the reset terminal RESET shown in FIG. 2, and instructs a reset process for setting an initial state when a power switch (not shown) is turned on.

The control unit 60 includes a ROM (read only memory) 70 that stores control programs, etc., a program counter for executing each step of this control program, and a program counter for executing each step of the control program, and deciphering various instructions read from each step to execute a job. This includes an instruction decoder, etc.

Next, each terminal of the microprocessor 41 having the above-described structure will be explained with reference to FIG.

First, the terminal OB is used to emit a signal to cause the buzzer 46 to sound when a key on the operating section 16 is operated, when cooking is finished, etc. The terminal IC ₁ is for inputting the on/off state of the normally open contact 452 (interlocked with the contact 451) of the door switch, that is, the closed/open state of the door 14, to the microprocessor 41. 41 determines whether to interrupt or prohibit the operation.

IT ₁ to _{IT 8} are for obtaining external mechanical component status information, and OD ₆ and OD ₇ provide timing pulses thereof. The terminals OD _S1 to OD _S7 are for outputting display data signals to the display section 15.
OD _G1 to _{OD G4} send a pulse signal to the display section 15 as a digit information timing signal, and a terminal to the operation section 16.
Like OD ₅ , it is issued as a control signal.

Terminals IK ₁ to _{IK 4} are terminals for accepting key input from the operation section 16, and the operation section 16 is connected to the OD _G1
~The signal line connected to OD _G4 and OD ₅ is a column line, and IK ₁
It is configured in a matrix shape with the signal lines connected to IK ₄ as row lines, and each key arranged to short-circuit the intersections of this matrix allows a predetermined signal to be input to terminals IK ₁ to _{IK 4} . It is set as.

Others: reset terminal RESET, interrupt terminal
The INT, terminals OSC ₁ , OSC ₂ , and terminals for outputting signals OM, OP, and OH are as described above. Note that when a signal is input to the interrupt terminal INT, the microprocessor 41 interrupts the processing by the program up to that point and jumps to a specific address. Taking advantage of this characteristic, the time reference signal TB' is input and used as a reference signal for a clock or timer. Also, the aforementioned signal
By aligning the rising timing of OP with respect to the signal TB' input to the terminal INT, phase control of magnetron input is easily performed.

Next, the operation section 16 shown in FIG. 4 will be explained. FAST, SLOW displayed as CLOCK SET
Both keys are keys for setting the clock, and when either key is pressed, the time displayed on the display 15 is updated (fast when FAST is pressed, slow when SLOW is pressed). When the key is released when the correct time is reached, the time setting is completed.

The keys marked C1, C2, C3... are used to instruct cooking according to a sequence prepared in advance in the program.For example, for course 1 cooking specified by C1, stewing is performed after preliminary cooking. This mode is suitable for cases where this microwave oven functions as a microwave oven, and in the first half, the magnetron is set to maximum output, and in the second half, the magnetron is set to an appropriate level by controlling the duty ratio of the signal OP. The output is low. Also, for example, course 3 cooking specified by C3 is a mode suitable for turning fish over halfway through cooking to brown the fish. is set to a high level alternately by controlling the duty ratio of the signals OP and OH, and the average output of both the magnetron and heater is set to a low level, and in the latter half, only the heater is set to a high output.

T1 and T2 are knobs for setting the timer, and T1 sets the time for the first half (stage 1) of cooking, such as course 1 and course 3, and T2 sets the time for the second half (stage 2). The time is set. TC is a knob for setting the temperature inside the cooking chamber when using it as an oven by energizing only the heater. The START key is a key for instructing the start of operation according to the cooking program set by the keys C1, C2, . . . and the knobs T1, T2, etc.

The display section 15 consists of a fluorescent display tube, and in addition to displaying four-digit numbers in a Japanese character pattern, it also has a bar section that displays the selected course and the progress of cooking, that is, stages 1 and 2. There are 5 each on the top and bottom. The time as a clock, the set time or remaining time as a timer, etc. are displayed in the Japanese character pattern.

In the product of the present invention, when the magnetron 27 and the heater 50 are alternately energized as in stage 1 of course 3, the control signals OP and OH are controlled at the rising edge of both as shown in FIG. The problem is that the timing and the falling timing do not match, and the output is made so that one falls and the other rises. OP (or OH)
Time t from the falling edge of OH (or OP) to the rising edge of OH (or OP)
is 1/2Hz of the frequency of the AC commercial power supply used as the power supply for the product of this invention (for example, in the case of a 50Hz power supply,
10msec), which is also 1Hz
It is preferable that the time is more than 1 minute. Figure 6 is a signal
This is a timing chart showing changes in the high and low levels of OH and OP, and changes in the input current to both heating means, that is, the magnetron and the heater. When OP falls, both OH and OP remain at low level for a time t. Therefore, while the bidirectional thyristor 54 is off during this period, the bidirectional thyristor 24 is turned off at the phase when the current is zero, and thereafter the magnetron 27 and the heater 50 are turned off.
The input currents to both become 0. However, in FIG. 6, such a delay in turning off the bidirectional thyristor 24 is omitted, and the input current is shown to be 0 when OP changes to low level.

Then, after time t has passed since OP falls, OH
When the current rises, the bidirectional thyristor 54 turns on and the heater current flows, but at this time the steady current
A surge current of about twice Is flows instantaneously.
Then, when OH falls, both signals OP and OH become low level. During this time, the bidirectional thyristor 24 is off, while the bidirectional thyristor 54 is turned off at the phase when the current is zero, and thereafter the input currents to the magnetron 27 and the heater 50 are both zero. However, in FIG. 6, such a delay in turning off the bidirectional thyristor 54 is omitted, and the input current is shown to be 0 when OH changes to low level. Then, when OP rises after time t has passed since OH falls, as a result,
The bidirectional thyristor 24 turns on and the magnetron current begins to flow. In this case, 3 to 4 at steady state.
Double the surge current will flow.

Comparing this with the conventional control mode shown in FIG. 7, in this case OH and OP are complementary to high level. Therefore, the heater (or magnetron)
The next magnetron (or heater) starts to be energized before the steady energization is cut off, and at this time, the above-mentioned surge current (or)
will flow. In this case, the surge current or steady current Is will flow superimposed on it. In other words, as is clear from the comparison between the two figures, in the product of the present invention, the input current is brought to zero level by once interrupting the steady current Is, so the level of the peak value of the input current determined by the transient surge current is It is lower than the case shown in FIG. 7, and the unnecessary burden on related circuit components is reduced accordingly.

As mentioned above, phase control is performed to match the timing of turning on the magnetron 27 with the time reference signal TB' to match the minimum voltage change, but despite this, a surge current of the above level still flows. become. Therefore, from the viewpoint of circuit protection, in the product of the present invention, OP and OH are switched after a delay of time t, thereby preventing a situation in which both the magnetron and the heater are energized. On the other hand, since the bidirectional thyristors 24 and 54 are used as switch elements, as mentioned above, even if OP and OH become low level and the gate signal is no longer applied, the current flowing through them becomes 0. Not blocked. Therefore, it is necessary to take a value larger than at least 1/2 Hz of the power supply frequency as the time t. However, this is because there is always a phase in which the current value is 0.
By setting t to such a value, OP, OH
The current after the current changes to low level and the surge current are not superimposed on each other.

Also, considering the time delay of the control system as a whole, it is appropriate that the value of time t be a time corresponding to 1 Hz or more of the power supply frequency used.

FIG. 8 is a flowchart of a program set in the microprocessor 41 to perform the above-described control. The microprocessor 41 has a power supply frequency of, for example, 50Hz based on the time reference signal TB'.
If so, the magnetron and heater are alternately energized and the signals OP and OH are directly controlled every 0.1 seconds (5 Hz) according to the routine shown in FIG.

First, the heater flag indicating that the next energization order is the heater is checked. In the example, the order of magnetron energization and heater energization is 1.
Since the cycle is determined, first we will explain the case where the heater flag is reset (≠1), and then the magnetron flag is checked, which indicates that the next energization order is the magnetron. When the magnetron and heater are alternately energized, the magnetron flag is set (=1) when the heater flag is reset, so in the next step, the magnetron is turned on and the magnetron flag is reset. Next, a period counter (a counter that measures the period when the magnetron and heater are sequentially energized once each) counts down, but before the contents of this counter reach 0, they simultaneously count down and the magnetron's The remaining time of the duty timer that regulates the energization time becomes 0, the magnetron is turned off, and then the heater flag is set. In the next cycle, the heater flag is set (=1), so the heater is turned on and the heater flag is reset. The heater continues to be energized until the period counter reaches 0, and when the counter reaches 0, the heater is turned off and the magnetron flag is set. Note that after the magnetron is turned off, a duty timer is set for energizing the magnetron for the next cycle, and after the heater is turned off, a cycle counter is set for the next cycle. In this way, the magnetron and heater are alternately energized with the time t set at 0.1 seconds.

According to the present invention, in an electronically controlled cooking appliance in which each of the plurality of electric heating means driven by a commercial power supply is controlled to be energized alternately or sequentially by a corresponding bidirectional thyristor, one heating means is There is no superimposition of the surge current at the start of energization with the current due to the delay in turning off the bidirectional thyristor that had previously energized other heating means, and therefore an excessive input current can be avoided. Since the circuit components can be protected, the present invention greatly contributes to improving the reliability and lifespan of this type of cooker.

Further, according to the present invention, in order to prevent the above-mentioned current weight, from the time when the supply of the gate signal to the bidirectional thyristor corresponding to one heating means ends, at least M/(M: arbitrary integer,: commercial power supply frequency)
After a long period of time has elapsed, the supply of gate signals to bidirectional thyristors corresponding to other heating means is started, and at this time, by using a time reference pulse signal generated based on the commercial power supply waveform, Since this is to determine the elapse of the above-mentioned time,
It is possible to accurately determine the elapsed time, and therefore, the next bidirectional thyristor drive can be performed while reliably eliminating the delay period for turning off the bidirectional thyristor, which depends on the power supply waveform.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which Fig. 1 is an external view of the product of the present invention, Fig. 2 is an electric circuit diagram thereof, Fig. 3 is a schematic diagram of the display section, and Fig. 4 is an operation diagram. 5 is a schematic diagram of the microprocessor, FIG. 6 is an explanatory diagram of the operation of the product of the present invention, FIG. 7 is an explanatory diagram of the conventional control mode, and FIG. 8 is a diagram of the product of the present invention. This is a flowchart of the program. 27...Magnetron, 24,25...Bidirectional thyristor, 37,57...Photocoupler, 4
1...Microprocessor, 50...Heater.

Claims (1)

[Scope of Claims] 1. A plurality of electrical heating means driven by a commercial power supply, a time reference pulse signal generation section that generates a time reference pulse signal based on the commercial power supply waveform, and energization of each of the heating means. and an electronic control section that selectively supplies gate signals to each of the bidirectional thyristors so as to energize each heating means alternately or sequentially. The control unit includes means for determining the elapse of a time length of M/(M: arbitrary integer, commercial power supply frequency) based on the time reference pulse signal, and also includes a gate to a bidirectional thyristor corresponding to one heating means. An electronically controlled cooking appliance characterized in that the supply of the gate signal to the bidirectional thyristor corresponding to the other heating means is started at least after the elapse of the above-mentioned length of time from the end of the supply of the signal. 2. The electronically controlled cooking appliance according to claim 1, wherein the electric heating means is a magnetron and a resistance heating element.