JPH0492390A - Microwave oven - Google Patents

Abstract

PURPOSE:To inform an user of an abnormal condition in energizing a microwave source by sampling signals indicating humidity in an oven, knowing the generation of microwaves, and thereby informing the user of it. CONSTITUTION:The timing signal 58 of a first group is generated first at the time of starting. A timing signal selection means 44 responds to the timing signal 58 so as to perform the sampling of humidity signals, so that the result of it is thereby stored. In the second place, the timing signal selection means 14 issues a timing signal selection signal 60 requiring to select the timing signal of a second group, to a timing signal generating means 42. The timing signal generating means 42, upon receiving the signal, terminates to generate the timing signal of the first group, it starts generating the timing signal of the second group, it performs the sampling of humidity signals in response to the timing signal 60, and it judges whether or not microwaves are generated within the period of time when the timing signal is generated. And when it is found that no microwaves is generated in either way, an user is informed of the situation by sounding a buzzer for waning.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a microwave oven that determines whether or not a microwave source is energized, detects an abnormality in the microwave source, and notifies the user. be.

<Prior Art> FIG. 5 is a block diagram showing a typical example of a conventional microwave oven.

Referring to FIG. 5, the conventional microwave oven includes a microwave source 14 that is coupled to an AC power source 12 and generates microwaves every half wave of the power waveform of the AC power source 12; A humidity signal generator 18 is connected to the AC power source 12 and is connected to the AC power source 12 for each cycle of the power waveform. a timing signal generating means 20 that generates a timing signal at a predetermined position; and a microwave that samples a humidity signal in response to the timing signal and controls the operation of the microwave source 14 based on the sampled value. source control means 22. The humidity signal generator 18 includes, for example, a humidity sensor that detects the humidity in the oven and generates a weak signal, and an amplifier that amplifies the voltage change of the signal generated by the humidity sensor by, for example, about 200 times.

The operation of the conventional microwave oven 7>K i will be explained with reference to FIG.

The AC power source 12 supplies an AC current having a waveform shown in FIG. 6) During the period indicated by a in Figure 1a), microwaves are generated.

The food in Open 16 is heated (by microwave),
Generates water vapor. A humidity sensor detects this water vapor and generates a weak signal. This signal is amplified by an amplifier. However, during the period when the microwave generation source 14 is generating microwaves, the humidity sensor is affected by the microwaves. Therefore, the waveform of the humidity signal obtained from the humidity signal generator 18 is as shown in FIG. 6 ib). That is, during the period indicated by a in FIG. 6, 1cl, the waveform of the humidity signal is disturbed by the influence of microwaves. The timing signal generating means 20 generates a timing signal during a period when the microwave generation source 14 is not generating microwaves (a period indicated by b in FIG. 6 (at). The waveform of this timing signal is 1cl.The microwave source control means 22 samples the humidity signal in response to the timing signal.The microwave source control means 22 generates the microwave based on the value of the sampled humidity signal. It performs processing for so-called automatic cooking, such as turning on and off the power source.

FIG. 7 is a circuit diagram of a main part of an example of a microwave oven using a microcomputer.

Referring to FIG. 7, this circuit includes a primary coil connected to an AC power source 12, a high voltage transformer 24 for supplying high voltage power to a microwave generation source (not shown) on the secondary coil side, and an AC power source 12. A primary coil is connected to the power supply 12, and a power supply track 26 for producing low voltage alternating current and a humidity sensor 28 are provided.
, an amplifier 3o for amplifying the signal from the humidity sensor 28, a microcomputer 32 which performs functions as a microwave generation control means and a timing signal generation means according to a program, a DC current supplied to the microcomputer 82, and a microcomputer 32 that functions as a microwave generation control means and a timing signal generation means. a rectifier circuit 34 for generating an external interrupt signal 64 that determines a reference value for the operation of the rectifier circuit 32; a capacitor 36 and a stabilizer for converting the full-wave rectified current output from the rectifier circuit 34 into a stable DC current; 38. One terminal of the rectifier circuit 34 connected to the power transformer 26 is connected to an external interrupt terminal INT of the microcomputer 32. The output of amplifier 3° is the address line ADo of the microcomputer.

Connected to ADl.

The alternating current supplied by the alternating current power supply 12 is boosted by the high voltage transformer 24 and is applied to the microwave generation source. The alternating current supplied by the alternating current power supply 12 is also stepped down by the power transformer 26. The stepped-down alternating current is rectified by the rectifier circuit 34, and even when it is a negative wave, it is converted into a current having a waveform in the same direction as a positive wave. The converted current is converted into a highly stable DC current 11 by the capacitor 36 and the stabilizer 38, and is supplied to the microcomputer 82.

Further, from one terminal of the rectifier circuit 34, an external interrupt signal 64 obtained by extracting only the negative wave of the alternating current is output and inputted to the external interrupt terminal INT of the microcomputer 32. The humidity sensor 28 detects the humidity inside the oven and outputs a weak signal. The amplifier 30 absorbs the voltage change of this weak signal by approximately 2
The humidity signal is amplified by a factor of 00 and input to the microcomputer 32. The microcomputer 32 is
A timer is started based on the time point when the external interrupt signal is generated, and the humidity signal is sampled when the microwave is not generated after a predetermined time.

The microcomputer 82 controls the microwave generation source based on the sampled humidity signal.

<Problems to be Solved by the Invention> The conventional microwave oven described above has the following problems.

Even if the microwave is no longer energized for some reason, it has not been possible to detect this and notify the user of the abnormality. (However, in models such as commercial microwave ovens that have two magnetrons and are energized in half waves, it heats up even if one magnetron is not working, making it difficult to notice an abnormality, so expensive detection equipment is required.) Furthermore, even if the microwaves were energized for some reason in a state other than heating, it was not possible to detect this and notify the user of the abnormality.

Therefore, it is an object of the present invention to provide a microwave oven that can notify a user of an abnormality in the energization of a microwave source at low cost without using a new device.

<Means for solving the problems> The microwave oven according to the present invention is connected to an AC power source,
A microwave source is energized for each cycle of alternating current of an alternating current power supply, an oven in which dielectric heating is performed by guiding the microwaves from the microwave source, and a humidity sensor that detects the humidity inside the oven. means for generating a signal;
a timing signal generating means for generating a first set and a second set of timing signals having mutually different phases that are generated every cycle of the AC power supply; and a first set of timing signals and a second set of timing signals. microwave source energization determination means for sampling the humidity signal in response to the signal and determining whether the microwave source is energized based on the sampled value; a microwave source abnormality determining means for determining an abnormality when the microwave source is not energized at a timing, and energizing the microwave source by the sampling when the microwave source is not energized with power by the microwave source drive circuit. If so, the microwave source drive circuit includes a microwave source drive circuit abnormality determining means that determines that the microwave source drive circuit has failed, and a notification means that notifies the user when both of the abnormality determining means determine that there is an abnormality.

<Function> The humidity signal includes noise due to the influence of the microwave during the period in which the microwave is being generated. The timing signal generating means first generates a first set of timing signals.

The first set of timing signals is either always generated within the same time period as the microwave, or always generated within a different time period. Timing signal generating means generates a humidity signal in response to the first set of timing signals.

Ring. The timing signal selection means determines whether the sampled humidity signal includes noise due to the influence of microwaves, and then the timing signal selection means instructs the timing signal generation means to switch to the second set of timing signals. Determine whether or not it contains noise. If noise is not included in either, it is determined that the microwave is not energized, and if noise is included other than during heating, it is determined that the microwave is energized. and sounds the alarm sound.

Embodiment> FIG. 1 is a block diagram showing the basic configuration of a microwave oven according to an embodiment of the present invention.

Referring to FIG. 1, this microwave oven is connected to an AC power source 12, and microwaves are guided inside from a microwave source 14 and a microwave source 4 that generate microwaves every half wave of the power waveform of the AC power source 12. an oven 16 which performs dielectric heating on food; a humidity signal generator 18 which detects humidity within the oven 16 and generates a humidity signal;
Timing signal generating means coupled to the AC power supply 12 and selectively generating a first set of timing signals and a second set of timing signals having mutually different phases for each cycle of AC of the AC power supply 12; 42, sampling the humidity signal in response to the first set of timing signals, and determining that no microwave is generated from the first set of timing signals and the second set of timing signals for the sampled values; Timing signal selection means 44 for selecting the timing signal corresponding to the period, and timing signal generation means 42
a control circuit that samples the humidity signal in response to a timing signal generated by the microwave generator and controls operation of the microwave source 14 based on the sampled value; and a microwave generator that energizes the microwave source 14. and a microwave source control means 22 consisting of a source driving circuit.

The operation of the microwave oven will be explained with reference to FIG.

The AC power supply 12 supplies AC having the waveform shown in FIG. Microwaves are generated during the period indicated by a in Figure fa). Food in the oven 16 is heated by microwaves to generate water vapor. Humidity signal generator 18 detects water vapor in the cigarette and generates a humidity signal. However, during the period when the microwave generation source 14 is generating microwaves, the humidity signal is affected by the microwaves.

Therefore, the waveform of the humidity signal obtained from the humidity signal generator 18 is as shown in FIG. 3, idl.

That is, during the period indicated by a in FIG. 8 [al], the waveform of the humidity signal is disturbed by the influence of microwaves.

The microwave oven first generates a first set of timing signals 58 upon startup. Timing signal selection means 44
samples and stores the humidity signal in response to the first set of timing signals 58 .

Next, the timing signal selection signal 60 indicates that the timing signal selection means 44id should select the second set of timing signals.
is sent to the timing signal generating means 42. When the timing signal generating means 42 receives the above-mentioned signal, it ceases generating the first set of timing signals, generates the second set of timing signals, and samples the humidity signal in response to the timing signal 60; It is determined whether or not microwaves are being generated within the period in which they are being generated, and if microwaves are not being generated in either of them, the user is notified of the abnormality by a notification sound.

In addition, the humidity signal is sampled even during heating, and it is determined whether microwaves are being generated. If microwaves are being generated, the user is notified of an abnormality by a notification sound.

The determination as to whether the microwave is energized is made, for example, as follows. If the first set of timing signals 58
is generated during the period in which microwaves are being generated. At this time, the timing signal selection means 44 selects υ
Noise is mixed in the sampled humidity signal. When sampling is performed multiple times, each sampling value contains noise. Since these noises are considered to be random, it can be determined that the absolute value of the difference between each sampling value is of a certain magnitude.

On the other hand, assume that the first set of timing signals 58 is generated during a period in which microwaves are not being generated. In this case, the humidity signal sampled by the timing signal selection means 44 correctly represents the humidity within the open air. When sampling is performed multiple times, the time interval between each sampling is equal to one cycle of alternating current of the alternating current power source, and is very short. It is thought that the humidity inside the open space will hardly change within a very short period of time. Therefore, in this case, the difference between two consecutive sampling values is almost 0.
is equal to

Therefore, it can be determined whether the microwave is energized as follows. First, a value is determined as a reference value for the above-mentioned judgment. Then, for example, sampling using the first set of timing signals is performed twice in succession. If the absolute value of the difference between these two sampling values is larger than the reference value, it is determined that the microwave is energized during sampling using the first set of timing signals.

This reference value may be determined, for example, through experiments.

FIG. 2 is a diagram showing the configuration of an embodiment of the present invention including a microcomputer.

Referring to FIG. 2, the microwave oven includes a microwave source 14 coupled to an AC power source 12 and generating microwaves every half wave of each cycle of the AC power source 14, and a microwave source 14 connected to the AC power source 12 by known means. a direct current generating circuit 46 that generates a direct current; an external interrupt signal generating means 48 that is connected to the alternating current power supply 12 and generates an external interrupt signal 64 for each cycle of alternating current by known means; An oven 16 that houses an object to be heated such as food and performs dielectric heating by guiding microwaves inside the oven, a humidity sensor 28 that detects the humidity inside the oven 16 and generates a weak signal, and a humidity sensor 2.
It is connected to an amplifier 30 that amplifies the voltage fluctuation of the output of No. 8 by about 200 times to generate a humidity signal, a DC current generation circuit 46, and an external interrupt signal generation means 48, and samples the humidity signal and converts it into a sampled value. Based on microwave source 1
and a microcomputer 50 for controlling 4. The microcomputer 50 includes an operation section 52 provided with keys for operating the microwave oven, a display section 54 for displaying cooking status such as cooking time and temperature inside the oven, and a display section 54 for displaying cooking status such as cooking time and temperature inside the oven. A speaker 56 is connected to generate a notification sound when an abnormality occurs. The microcomputer 50 operates according to a built-in program to realize the functions of timing signal generation means, timing signal selection means, and microwave generation source control means.

A flowchart of this program is shown in FIG.

Note that this flowchart will be explained in detail later.

The operation of this microwave oven will be explained with reference to FIG.

The alternating current supplied by the alternating current power supply 12 is converted by the direct current generating circuit 46 into a direct current having a voltage suitable for driving the microcomputer 50 and is supplied to the microcomputer 50 .

The AC waveform of the AC power supply 2 is shown in FIG. 3 (al).

The external interrupt signal generating means 48 generates an external interrupt signal having a waveform shown in FIG. input.

Because of the external interrupt signal, inside the microcomputer 5o,
An external interrupt occurs at the timing shown in FIG. 3 1a). This external interrupt establishes a reference value for timing the sampling of the humidity signal by the microcomputer.

Powered by AC power source 12, microwave source 14 generates microwaves every half wave of each cycle of AC. In this microwave oven, the phase in which microwaves are generated is not particularly determined at the time of design. Therefore, there is a first case in which microwaves are generated during the period indicated by a in Figure 8 fal, a second case in which microwaves are generated during the period indicated by b, and a case in which microwaves are not generated in either case. There are three possible ways. The microcomputer 50 uses a timer that uses the occurrence of an external interrupt as a reference time.
The humidity signal is sampled by switching between the first delay time t1 shown in FIG. 3 iel and the second delay time t2 shown in FIG. 3 fgl. This switching is done by a program.

The operator places the food in the oven 16 and starts the microwave oven using the operating section 52. It is assumed that the waveform of the humidity signal of this microwave oven is shown in Fig. 8). The microcomputer 5074 first samples the humidity signal using the first delay time t1 and the second delay time t2 shown in FIG. Whether or not each sampled signal contains noise can be determined by sampling multiple times as described above. This determination is also made by the program, and if neither signal contains noise, it is determined that there is an abnormality and a notification sound is sounded.

! In addition, the humidity signal is sampled even during heating, and if the signal contains noise, it is determined that there is an abnormality and an alarm sounds.

FIG. 4 is a flowchart of a program executed by the microcomputer 50.

Referring to FIG. 4, in step S2 of this program, variables TOTAL 1 and 2 are set to zero.

This is a default process. Further step S
At step 3, program progress is halted until there is an external interrupt. When an external interrupt occurs, the flow proceeds to step S4.
Proceed to. In step S4, the first delay time 1.
Flow progress is stopped during this period. First delay time t1
Afterwards, A/D conversion is performed on the humidity signal and the digitized humidity level is set in variable A. After a further second delay time t2, the humidity level is set to variable C.

Step S6 includes steps S7 to 5ll-t.
This is preparation work for repeated processing. In step S6, the control variable 1 of the loop is set to zero. In step S7, progress of the program is stopped until an external interrupt occurs. In step S8, immediately after the external interrupt, processing is unconditionally postponed for a first delay time [1].

Thereafter, in step S9, the contents of variable A are stored in variable B, the humidity signal is sampled, and the humidity level is set in variable A. Then, the difference between the humidity level obtained this time and the humidity level obtained last time is added to the variable TOTAL 1. Further, after a delay time L2, it is added to TOTAL2 in the same way. At step 510, control variables I and 10 are compared.

If the control variable I is equal to 10, the flow proceeds to step 512, otherwise the flow returns to step S7.

When the flow advances to step 512, steps 87 to 5
As a result of the processing in step 11, the absolute values of the differences in humidity levels from two consecutive samplings are totaled and stored in the variable TOTAL for 10 times.

By summing the values 10 times, the measurement error included in the contents of the variable TOTAL is reduced, and the determination at step 512 becomes more accurate.

In step 512, variables TOTAL 1 and 2
A comparison is made between the contents of and a predetermined value X.

It is assumed that the humidity level is converted into 2" = 256 steps, that is, each level from 0 to 255, by A/D conversion when the humidity signal is normally sampled. From experiments, it is assumed that X is approximately 10. It is sufficient if the variable T
If the contents of OTAL 1 and 2 are both smaller than X, it is determined that the microwave is not energized at either timing, and the process proceeds to step 151g.

Furthermore, if either of the contents of TOTAL 1 or TOTAL 2 is greater than X, it is determined that the microwave is being energized, and the process proceeds to step 514.

In step 518, it is determined whether microwave heating is in progress, and if microwave heating is in progress, a notification sound is generated because the microwave is not energized.

At step 514, it is also determined whether microwave heating is in progress, and if not, a notification sound is generated because the microwave is energized.

As mentioned above, in this example, the noise generated in the humidity signal by microwaves is random, and when a humidity signal that does not contain noise is sampled multiple times in a short period of time, each sampling value is Using the fact that there is a strong correlation, it is possible to know whether the microwave is energized or not.

Note that this invention is not limited to the above-described embodiments.

For example, the flowchart shown in FIG. 4 is only one example, and various other programs can be considered for realizing the present invention.

<Effects of the Invention> The microwave oven according to the present invention includes means for generating first and second sets of timing signals with mutually different phases for each cycle of AC power supply, and means for generating first and second sets of timing signals with mutually different phases. The apparatus includes means for sampling a humidity signal indicating the humidity in the open air, and for notifying whether or not microwaves are being generated based on the sampled value.

Therefore, regardless of whether the microwaves generated in the microwave oven are energized by the positive or negative half-wave of the AC power supply, whether the microwaves are energized during microwave heating or not,
In addition, it is possible to determine whether the microwave is being energized for reasons other than the microwave ferry being energized.

Therefore, it is possible to notify the user of an abnormality more quickly. Furthermore, it can be applied to a two-pipe type case such as for commercial use.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of an embodiment using the microcomputer of the present invention, and FIG. 3 is a timing chart showing the operation of the device shown in FIG. 4 is a flowchart of a program for implementing the present invention using a microcomputer, FIG. 5 is a block diagram of a conventional microwave oven, and FIG. 6 shows the operation of the conventional device. Figure 7 is a schematic circuit diagram of my conventional device. In the figure, 12 is an AC power supply, 14 is a microwave generation source, and 16
18 is an oven, 18 is a humidity signal generator, 22 is a microwave source control means, 42 is a timing signal generator, 4
4 is a timing signal selection means, 50 is a microcomputer, 58 is a first timing signal, and 62 is a selected timing signal. In addition, the same reference numerals in the figures indicate the same or equivalent parts. Agent Patent Attorney Ume 1) Katsu (and 2 others) 1% 1 Zuho Leap 3 Figure 5

Claims (1)

[Scope of Claims] 1. A microwave power supply drive circuit connected to an AC power supply and energizing power to a microwave source in each cycle of AC of the AC power supply; means for detecting humidity in the oven to generate a humidity signal; a first set of mutually different phases generated every cycle of the AC power supply; timing signal generating means for generating a second set of timing signals; sampling the humidity signal in response to the first set of timing signals and the second set of timing signals; a microwave source energization determination means for determining whether the microwave source is energized, wherein the microwave source is not energized at both timings of the first set and the second set; microwave source abnormality determining means for determining that the microwave source is abnormal if the microwave source is not powered by the microwave source drive circuit; and if the microwave source is powered by the sampling when the microwave source is not powered by the microwave source drive circuit; 1. A microwave oven comprising: a microwave source drive circuit abnormality determination means for determining that the abnormality has occurred; and a notification means for notifying a user when both of the abnormality determination means determine that there is an abnormality.