Note: Descriptions are shown in the official language in which they were submitted.
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SPECIFICATION
TITLE: Heating Appliance
TECHNICAL FIELD
This invantion relates to safety means for such
heating appliances having a digital control section as
electric ovens! microwave ovens, and composite ovens
which comprise the two preceding types~ wherein the
preheating completion time is estimated and reported,
the completion of preparation for cooking is detected
by the opening and closing of the door, the time for
pushing the start switch is reported, and the completion
of preparation is reported upon ascertainment of the
completion of timer setting.
B~CKGROUND ART
The recent development of semiconductor technology
is remarkable, and incorporation of electronic circuits
in control systems is increasing rapidly. With the
advent of stored logic type controllers represented by
the microcomputer, digitali~ation of control systems is
also increasing rapidly.
In the field of heating appliances also, the wave
of such digitalization has changed the arrangement of
control systems and the configuration of operating
panels to a large extent. New functions which would be
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impossible to attain with conventional discrete circuits
have been added one aEter another.
However, such digitalization of opera-ting ~anels
and adaptation of heati~g appliances for mul-tifunction
can complicate the operation of the appliance, resulting
in an increasing tendency for the user to e~perience
troubles; she fails to fully utilize the "helpful"
functions or erroneously operates the appliance, leading
to unsatisfactory heating. Even a failure of part of
the circuitry can cause the control system to run away,
contrary to the user's intention.
Accordingly, there has been a desire for a heating
appliance which will never start heating until the user
has set desired data on heating, will report to the user
the acceptance of the effective heating data by the
control system to thereby make the operation readily
understandable, and is capable of preventing the control
system from running away even in the event of a failure.
As for an error often found particularly in the
composite oven, the user forgets to do the idle heating,
which is called preheating, (i.e., heating with no load
put in the heating chamber) and consequentl~ fails in
cooking or by mistake she dose the idle heating for a
cooking mode which forbids it. The number of such errors
is increasing.
The manner of operating the heating appLiance largely
depends on differences in -the type of heat source and in
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the method of heating food.
First, reference will be given -to heating appliances
equipped with an electric heater or gas burner as a heat
source, such as an oven`(hot oven) and grill. These heat
sources heat food externally. Further, these heating
methods can be roughly classified into two types by the
heating mechanism, as follows.
One type ls oven heating wherein food is baked in a
heated atmosphere. This is a heating method wherein food
ls baked in a high temperature atmosphere with the radiant
heat from the heat source being prevented from reaching
the food. In this case, it is necessary to sufficiently
elevate the temperature in the heating chamber prior to
putting food therein. That is, idle heating called pre-
heating must be done. Neglectiny this would require a
longer heating time or even cause a failure in cooking
depending upon the kind of dish.
The other type is grill heating wherein food is baked
by the radiant heat from the heat source. This type dose
not require preheating since baking is carried out by the
infrared radia-tion from the heat source. If preheating is
performed by mistake, the interior of the heating chamber
will reach a considerably high temperature in a short
time , entailing danger. The user will be given a rough
estimate of the required` heating time for grill heating
under conditio~s not including unnecessary preheating;
thus, preheating would result ln a scorch.
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While the foregoing reEers to the difference based
on the presence or absence of preheat:ing, there is
another great difference in operation be-tween oven heating
and grill heating. It lies in restart after the door is
opened in the course of heating. Generally, -the heat
source used for oven heating is a sheathed heater which
emits less radiation, so that the heater itself takes
some time in raising the temperature in the heating
chamber. Thus, it is often so arranged that once heating
is started, electric supply to the sheathed heater is
continued even if the door is opened in between. Of course,
temperature con-trol is performed. In shch case, therefore,
oven heating is restarted simply by the user closing the
door again.
On the other hand, used for the grill heating are a
quartz tube heater and special sheathed heater which emit
infrared radiation at high rates. These heaters exhibit
a satisfactory rise in infrared radlation. There is no
need to maintain the interior of the heating chamber at
high temperature. Thus, if the door is opened during
heating, electric supply to the heater will be cut off to
protec-t the user against a burn. Thus, it is mos-tly so
arranged that the start key myst be pressed again for
restart.
Reference will now be given to such heating appliances
as a microwave oven, equipped with a microwave generator,
e.g., a nagne-tron. Microwave heating heats an object
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internally and externally at the same time and needs no
preheat:ing. If, therefore, preheating (i.e., idle
heating) is efEected by mistake, though there is no
danger of scorching as in grill heating this can be very
dangerous since it results in an increased leakage of
micrawaves from the main body and in overheating local
portions of the heating chamber (where the standing waves
are strong). Further, it damages the magnetron, shorten-
ing its life. In other words, idle heating in the micro-
wave oven is a strict prohibition.
For prevention of idle heating, the microwave oven
must be so arranged that the s-tart key must be pressed
before heating can be restarted, each time the door is
closed.
As described above, the manner of operation widely
differs according to differences in heat source and heating
method. Moreover, composite heating appliances in which
these oven, grill and microwave heating methods are
integrated are coming to have a share of the greater part
of the demand. Thus,the Nser should accurately remember
and carry out the disparate operations for the respective
heating methods. A mistake in these operations entails
not only a failure in cooking but also possible dangers
of hurting the person and even causing a fire.
Thus, prehea-ting has been a difficult thing particu-
larly -to the cpmposite oven, as described above~ Moreover,
preheating has the following problems left unsoLved.
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How to carry out preheating -there are three methods,
roughly clssified. ~ first method is to set a necessary
preheating temperature and wait until heating -to this
temperature. This is the intrinsic form of preheating,
superior ln the functional aspect of elevati~g the tem-
perature in the heating chamber to a predetermined value,
and is capable of cpmpleting preheating in a shorter -time
than any of the other methods which follow, though it
dose not allow the user to leave the heating appliance
since how long preheating will take is unknown.
A second method is to set a heating time alone and
continue electric supply to the heater or the like serving
as heating means until lapse of said time. The time at
which preheating ends is obvious, so that this method is
the most simple and convenient method for the user. However,
since the preheating temperature is directly influenced
by the heating chamber temperatue and the source voltage
at the start of preheating, different preheating tem-
peratures will result; thus, this method is inferior in
functional aspect.
A third method, which is a combination of the preceding
two methods, is to set both a preheating temperature and
a preheating time. According to this method, after the
preheating temperature is reached, temperature control is
performed until lapse of the preset time; thus, this
method is superior both in functional aspect ancl in operating
aspect in that the preheating completion time is made known~
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As compared with the first method, however, it requres
extra time and energy. The operating procedure is also
increased, imposing an increased burden on the user.
DISCLOSURE OF THE INVENTION
With the above in mind, the present invention has
for i-ts object the provision of a heating appliance
which will never start heating until the user has set
desired data on heating, will report to the user the
acceptance of the effective heating data by the control
system by using a synthsized voice or-other means to
thereby make the operation readily understandable, and
is capable of preventing the control system from running
away even in the event of a failure.
Further, the invention realizes the provision of a
heating appliance which notifies the user of the presence
or absence of an object to be~heated and of the time for
operating the start switch and which detects the open-
ing and closing of the door to indirectly infer the pres-
ence or absence of an object put therein so as to advance
the heating sequence by one step, thus ensuring a safe
operation.
The invention also provides a system adapted to
complete heating with a minimum of time end energy involved
and -to estimate and repor-t the preheating completion time.
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The above noted objects of the invention may be
efected by providing: a hea~ing appliance comprising a
heating chamber to receive an object to be heated therein,
heating means connected to said heating charnber, a main
control section for controlling electric supply to said
heating means, a memory for storing data on heating, input
means for inputtiny said data, timer means, and reporting
means, the arrangement being such that when data on heating
is inputted or corrected or corrected by said input means,
said timer is started, and if there is no data inputted
during the counting of a predetermined time, said main
control section judges that the setting or correction of
data on heating has been completed, and causes said report-
ing means to make a report to the effect that it is possible
to start heating.
The objects may be further ef~ected by providing:
a heating appliance comprising a heating chamber to receive
an object to be heated therein, heating means connected to
said heating means, a door installed on the opening in said
heating chamber so that it can be opened and closed, means
for detecting the opening and closing movement of said door,
a main control section for controlling electric supply to
said heating means, input means for inputting into registers
data on heating temperature and heating time for a certaln
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heating operation or means for transferring these heating
pattern data from a memory in which they are stored to
predetermined registers, and reporting means for reporting
the progress of heating, the arrangement being such that the
main control section detects the opening and closing move-
ment of said door by using said door opening and closing
movement detecting means, controls the progress of the
heating pattern set in said registers on th~Q basis of said
detection, and causes said reporting means to report the
essentials of operation necessary for the progress.
The above noted objects may be still furthQr
effected by providing: a heating appliance comprising a
heating chamber to receive an object to be heated therein,
heating means connected to said heating chamber, sensor
means capable of directly or indirectly detecting the
temperature in the heating chamber, a main control sec~ion
for controlling electric supply to said heating means on the
basis of temperature information inputted by said sensor
means, a memory having stored therein data on heating
temperatures and heating times for performing certain
heating operations, heating selection means for reading a
heating pattern out of the memory and instructing the main
control section to effect electric supply to the heating
means in accordance with said heating pattern, and reporting
means for reporting the progress of heatin~, the arrangement
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being such that the main control section detects the temper-
ature before or immediately after the start of heating by
using said sensor, calculates or estimates on the basis of
said detection an approximate time taken for the interior of
the heating chamber to reach the predetermined temperature,
and causes said reporting means to report said approximate
time at least in two ways.
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BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a prespective view of a main body, showing
an emboidiment of the invention;
Fig. 2 is a detailed view of the principal por-tion
of said main body;
Fig. 3 is a system block diagram of the same;
Fig. 4 is a circuit diagram, showing a concrete
example of saidblock diagram;
Fig. 5 is a flowchart showing a program arrangement
for detection of completion of setting;
Fig. 6 is a Elowchart showing a program arrangement
for control of heating;
Fig. 7 shows a concrete e~ample of preheating con-
trol; and
Fig. 8 is a diagram showing temperature rise charac-
teristics in a heating chamber.
BEST MODE OF CARRYING OUT THE INVENTION
Fig. 1 is a perspective view of the main body of a
heating appliance, showing an embodiment of the invention.
The main body 1 has a door 2 pivotally mounted on the
front surface thereof, said body being provided with an
operating panel 3. Arranged on the operating panel 3 are
a keyboard 4 and numerical-value setting knobs 5 serving
~25 as input means enabling the user to give various instruc-
tions to the control system. The numeral 6 denotes an
indicator window Eor indicating heating data which is se-t
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through said input means, and 7 deno-tes a vocal port for
delivering synthsized voices.
Fig. 2 is a detailed view of the principal portion.
Arranged on the keyboard 4 are various function keys
'i or giving instructions on heating modes to the control
sys-tem. The numerical-value setting knobs comprise a
~lme knob 5a for inputting "time/weight" and ~ temperature
knob 5b for inputting "temperature". The time knob 5a is
capable of inputting a heating time for each mode and the
]0 weight of an object to be heated for a "weight thawing"
mode, while the temperature knob 5b is capable of inputting
chamber temperatures for grill and oven modes.
Arranged in the indicator window 6 are a numeral
indicating section 6a for indicating a heating time or
weight, temperature bars 6b for indicating temperatures,
and a mode status 6c for indicating heating modes.
A weight thawing key ~ is used to cause the control
system to calculate the heating time by inputting the
weight o~ an object to be heated; thus, it clears the
user of the burden of conversion to the heating time.
At this time, in the indicator window 6 a "g" status 6b
is lighted to indicate the inputted weight.
A start key 9 is used to give an instruction to star-t
heating and a clear key 10 is used to stop heating or
cancel a program.
Fig. 3 is a block diagram showing the system arrange
ment of the heating appliance. In~talled in a heating
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chamber 11 are a magnetron 12 and heaters 13 and 14,
which are heating means, -to supply -thermal energy to an
object to be heated 15. Electric supp:Ly to these heating
means is controlled by a main control section 16. The
S numeral 17 denotes an electric supply control section
including switching means, such as a relay, and a driver
for dri~ing it.
Data on heating is inputted into the main control
sec-tion 16 from the keyboard 4 and also from volumes 18a,
18b connected to the knobs Sa, 5b. The numeral 19 denotes
an A/D converter for reading in the resistance values of
the volumes. Suçh volumes may be constructed of a
rotary encoder. The data on heating inpu-tted by such
input means is stored in a RAM in the main control section
]5 16. Heating is controlled on the basis of da-ta on heating.
Further, such da-ta on heating is displayed by display
means 20.
The openingandclosingmovement of the door 2 is
detected by a door switch 21 serving as door opening and
closing detecting means and is inputted into -the main
control section 16.
The numeral 22 denotes a thermistor serving as
sensor means for detecting the temperature in the heating
chamber 11. The numeral 23 denotes a detection circuit
B for reading variations in the resistance value of the
thermistor and inputting them into -the microcomputer,
said detection circuit being construc-ted, e.g., of an A/D
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converter.
The numeral 24 denotes a detection circui-t C for
monitoring -the source voltage. It may be constructed,
e.g., of an A/D converter or it may be a comparison
circuit for comparison with a reference voltage, formed
of a simpler device, e.g., a zener diode.
VoLce synthesizing means comprises a synthesizer
25, a voice memory 26, and a speaker 27.
The voice memory 26 has voice data stored therein
to allow the synthesizer 25 to read out said voice data
so as to synthesize voice signals. These voice signals
are transferred to the speaker 27 and converted into
voices.
The numeral 28 denotes a sensor for detecting the
progress of heatingl and 29 denotes a detection circuit
therefor. The sensor 28 may be in the form of a ther-
mistor for detecting the temperature in the hea-ting
chamber 11, a humidity sensor for detecting vapor being
evolved from -the object 15, or an infrared sensor for
detecting infrared rays being emitted from the object 15.
Fig. 4 is a circuit diagram showing an embodiment
of said system. The main control section 16 is constituted
of a controller of the stored program type, e.g., a one-
chip microcomputer. Such microcomputer 16 controls
electric supply to the magnetron 12 or to the heaters 13,
14, through a relay driver representing the electric
supply control section 17. A time relay 30 is a relay
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adapted to be continuously closed during this electric
supply. A power relay 31 is a relay adapted to be
intermittently closed during this electric supply and
a~t to change the average output from the magnetron 12
or heaters 13, 14. The numeral 32 denotes a switchlng
relay for controlling switching between the magnetron
12 and the heaters 13, 14.
In addition, 33 denotes a main circuit door sw:itch
for breaking and making the main circuit in response to
the opening and closing of the door; 34 denotes an interior
]amp; and 35 deno-tes a motor for a cooling- fan or the like.
Data on heating are inputted into the miCrQcomputer
16 from the keyboard 4 and from the volumes l~a, 18b.
A/Dl and A/D2 denote A/D input terminalsl containing A/D
converters. The keyboard 4 has a key matrix built thereon,
swept by outputs Ro~R3 and connected to input terminals
I -I .
The do~r switch 21 is swept by an output R4 znd
connected to the input terminal I3.
The sweep outpu-ts from the key matrix also serve
as grid control signals for the fluorescen-t display
tube 20 capable of dynamic lighting. The display -tube
20 comprises 6 grids and obtains display data from
outputs O0-O7.
The arrangement of various sensor means will now
be described. The numeral 22 denotes a thermistor or
detecting the -temperature in the heating chamber. It
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is connected to the A/D input terminal A/D3. The numeral
28 denotes a humidity sensor which detects the progress
of heating. It is connected to A/D4. The numeral 24
~ denotes a source voltage monitor which detects the voltage
S in -the main circuit. It is connected to A/D5.
Also inputted into the microcomputer 16 is a clock
slgnal which forms a basis for timer counting. The
numeral 36 denotes a clock circuit therefor.
The voice synthesizing means comprises the voice
syntheslzer 25, voice memory 26, and speaker 27. For this
synl:hesizer, for example, LSI based on PARCOR synthesizing
method is employed. The numeral 37 denotes an audio
amplifier which drives the speaker 27. The readout address
is outputted from the microcomp~ter 16 through Do-D3.
The microcomputer 16 controls the synthesizer by means
of Rg signal and I4 input.
In such arrangement, the procedure for inputting
data on heating and the method of control associaLed
therewith will now be described.
Fig. 5 is.a flowchart illustrating such procedure
and control. First, the microcomputer 16 waits for a
key 4 to be pressed, while displaying "O", (a).
When a key 4 is pressed, the mlcrocomputer decodes
it (b), and sets the corresponding heatlng mode (c).
Thus, the set heating mode is displayed on the display
tube 20, with "O" disappearing and with -the digit places
bei.ng all blank.
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In this condltion, the microcomputer 16 waits for
the volume 18 (18a, 18b) to be turned (d). As soon as
the volume 18 is turned, the microcomputer resets the
interior timer (e) and starts counting up (f). At this
time, a heating time which has been set appears in the
display tube 20.
~hen the interior timer counts a predetermined
time (2 seconds, in this example), -this results in time-
up (g). If the volume is turned again during this time
(h), the microcomputer judges that the setting of heating
ti.lne has not been completed, and it resets the timer
again and counts 2 seconds afresh. That is the sequence
will not proceed until the end of fine adjustmènt of
heating time made by the volume 18, followed by lapse of
2 seconds.
: Upon lapse of 2 seconds, the microcomputer 16 outputs
a predetermined voice selection signal to the synthesizer
25 and reports the completion of setting through the
speaker 27 (i). For example, in the case of grill heating
and microwave heating, it reports in synthesized voice,
"Put in your food and then press the cooking start key."
In the case of oven heating, it voices a warning. "Pre-
heating takes place first. With nothing pu-t in, press
the start key." Thereafter, the microcomputer 16 waits
fox the start key to be pressed.
The provision of such sequence ensures that operation
wi:ll not be started by mistake even iE -the star-t key is
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pressed when a heating time and temperature are not set
or are being set or even if noise causes misunderstanding.
Further, even if the start key is dameged and remains ON
or even if the volume brush and resistance pa-ttern get
out of order, the normal sequence is protected from being
executed, thus preventing start of heating. The former
results in the on-state of the start key being detected
before the volume is turned, so that such is neglected.
The latter results in the volume value fluctuating rather
than stabilized, so that the timer cannot count 2 seconds.
~rhus, the invention is not seriously influenced by actual
parts failures.
In addition, the setting completion report may be
made by a display tube, still providing the same effect.
However, the synthesized voice provides a higher warning
effect and is more concre-te.
Further, it is also possible to make a report con-
cerning the sensor 28 by using the voice synthesizing
section. For example, in the case of such a humidity
sensor as ~umiceram, as the temperature in the heating
chamber 11 rises, the humidity sensor exhibits thermistor
characteristics, failing to detect humidity changes.
Thus, a thermistor and a humidity sensor may be provided
as the sensor means and a program may be so prepared
that if the temperature in the heating chamber rises above
a certain level, a report is made to -the effect that
automatic cooking is impossible.
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An arrangement for advancing the heating sequence
depending upon the opening and closing movement of the
door will not be described with refexence -to Fig. 6.
After setting data on heating, the user opens
the door, puts an object ta be heated in the heating
chamber, and closes the door again. Thus, the micro-
computer can indirectly detect the placement of an
object in the heating chamber, from the opening and
closing movement of the door (j). Then, it advances the
heating sequence by one step, and waits for the start
key to be pressed. At the same t-ime, it makes a report
urging the user to do that, ("Press the s-tart key.")
In the case of oven heating, such operation on the
door is normally not performed, but if it is performed,
there isa possibility-that an object to be heated has
been placed by mistake, Thus, the microcomputer urges
the user to do the idle heating again, ("With nothing
put in,-press the start key.")
With an object to be heated placed or removed, as
requested, the-start key is then pressed (k). Thereupon,
the microcomputer starts electric supply to the indivi-
dual heating means and reports that heating is going to
be started, ~"Cooking begins.") In the case of oven
heating, an estimated preheating time report Z is made,
("Preheating will be over in about X minutes.") (This
will be later described in more detail.)
In addition, if the start key is pressed wi.-thout
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passing through the state j, i.e., without the opening
and closing of the door, -the microcompu-ter judges that
idle heating has been performed, and it will not start
electric supply to the heating means except for oven
heating. Thus, the danger of performing idle heating
is eliminated. In addition, the order of performing
key operation and object placement may be reversed.
In this case, nothing will be reported since preparation
for preheating is not completed at the time of placement.
Suppose that the door is opened during heating (1).
Thell, in the case of grill heating and oven heating,
the step j is followed, ("Press the start key."); in
the case of oven heating, the user i~s requested to
continue idle heating, ("Don't put in food until com-
pletion of preheating.") In this case, since it is
undesirable to lower the heater temperature, electric
supply to the heater is not stopped. Therefore, once
the door is closed, preheating is continued, so that
operation on the start key is not required nor is a
report made urging the user to do that.
After restart, time-up or the heating temperature
is reached (m), whereupon a report of the completion of
heating is made, ("It's finished.") In the case o oven
heating, the completion of preheating and a request for
placement of an object are announced, ("Preheating is
ovex. Put in your food and then press the star-t key. Il)
Subsequent placement of an object to be heated (n),
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operation on the start key, and report oE time-up or
of attainment of heating temperatu e (o) are the same
as in grill and microwave hea-ting.
While synthesized voices have been used as report~
ing means in this embodimen-t, other reporting means,
such as display tubes and LEDs are applicable, of course.
In Fig. 6~ it will be recalled that an estimated
preheating time report Z was executed; that is, it was
a report saying, "Preheating will be over in about X
minutes." This is per~ormed by the thermistor 22
detecting the temperature in'the heating chamber before
or immediately after the start key is pressed and by
the monitor 25 measuring the source voltaye.
On the basis of such measurements, the micro-
computer 1~ outputs the temperature of preheating to be
e~fected first i'nto the display section or the fluore-
scent display tube 20, estima-tes the time required for
the preheating, and reports said time in synthesized
voice through the voice synthesizing section comprising
the synthesizer 25, voice memory 26 and speaker 27.
While monitoring the source voltage is indispens-
able for strict estimation of preheating time, the
~ollowing expedient may be contemplated. Fig. 7 shows
a concrete embodiment oriented to automatic oven heatingO
Suppose that a key for automatic cooking 3 is pressed.
Then, the microcomputer produces a buzzer sound (pi)
and then reports the name of the menu corresponding -to
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the heating pattern, ("It's a butter roll.") Further,
- the display tube 20 outputs display data "~3" to indicate
that automatic cooking 3 has been effectively accepted.
The syntheslzer 25 subsequently reports that the pre-
heating sequence has been preset, ("Preheating takes
place first.")
When the start key is pressed, the microcomputer 16,
as already described, calculates or estimates the time
taken to reach the preheating temperature, from the tem-
perature in the heating chamber, and reports it in
synthesized voice, ("Preheating will be over in about 8
minutes.") The estinlated time is also displayed by the
numeral display section 6a. In the e~ample shown in
Fig. 7, whether the temperature in the heating chamber
is above 100C or not is taken into account in connection
with processing, the former case being referred to as
hot start and the la-tter as cold start. In the case of
hot start, a standard period of time (8 minutes) taken
to reach the preheating temperature (180C) for butter
rollsis reported, while with cold start a shorter period
of time is reported,("in a few minutes" or "in 2 -to 3
minutes"). As for temperature indication, the preheating
completion temperature is indicated by lighting and the
present time by blinking.
Upon completion of preheating, several times of
buzzing is followed by a report of the completion oE
pxeheating. ("Preheating is over.") Continuing temperature
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eontrol, the microcompllter waits for -the user to come
(wait cycle). Knowing an approximate -time of preheating
completion, the user will come back to the heating
appliance before that time. That is, without requiring
S constant attendance on the part of the user, such wait
time can be made very short~ Thus, the merit of the
first conventional method (a minimum of preheating time
and energy) and the merit of the second (knowable pre-
heating completion time) can be combined, and the wasteful
wait time and troublesome operation involved in the third
method are no longer required.
After wait cycle, when the user opens the door, the
microcomputer 16 makes a report about the cooking proce-
dure for main heating and about the attachments which
must be (or can be) used, ("Baking is by two-stage cooking.
Put your food in the footed plate.") Whereas in a heating
appliance ofthe microwave and hot oven combination type
the differential use ofvarious at-tachments has been
inevitable (e.g., metal plates for hot oven and glass
plates for microwave oven), the invention enables these
plates to be readily used each in its proper way.
Thus, the combined use of synthesized voices and
temperature sensors in the manner described above has
made it possible to e~ecute -the heretofore troublesome
preheating sequence in a simple operation ~ree from errors.
A method of more strictly estimating preheating
time by using the source voltage monitor 24 will ~ow be
. . . ,. ~ ~ . . - ;,
~L2~3~
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described. Fig. 8 is a graph showing heating chamber
temperature rise characteristics. Curve A represents a
standard pa-ttern starting at room -temperature, showing
that it takes 8 minutes for the temperature to reach
210C. If the source voltage changes, the temp~rature
gradient also changes. Curves B and C represent character-
is-tics at 110% voltage and 90~ voltage, respectively.
In the case of cur~es B and C, the standard time TS must
be corrected by an amount of QTl (1 minute) and ~T2 (1-2
minutes), respectively, and the corrected times will be
reported.
A manner of starting with the heating chamber already
heated to a certain extent will now be described. Curves
D and E predominate in thls case. Curve D represents a
situation where the heating chamber has considerably cooled,
i.e., some amount of time has passed since the last hea-ting.
The temperature in the region around the sensor is still
high, so that when stirring begins, the temperature in
the heating chamber becomes uniform, causing the temperature
around the sensor to drop temporarily. In such case,
therefore, though the sensor has already reached 100C
it does not follow that it is correct to sub-tract ~ minutes
from the standard pattern A. Actually, it takes 5 minutes.
The other curve E is found in a situation where
heating is interrupted on the way. That is, while the
heater chàmber is su~iciently high in temperature, the
temperature in the region around the sensor has not risen.
, . ~
._ .
. . .
~2a~~3~
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An example of this case i5 where the doox is opened
during preheating and preheating is restarted. In this
case, the preheating completion time is shorter than 4
minutes, being reduced to about 3 minutes.
Thus r ifthe temperature in the heating chamber and
the source voltage at the start of heating can be rneasured
and if the tendency of temperature rise immediately after
the start of heating can be detected, the preheating time
can be estimated with substantial accuracy. Accordingly,
temperature display can be provided by the display section
and a rough estimate oE the preheating time can be provided
by the voice synthesizer and display tube. While synthe-
sized voices have been used as reporting means in the
present embodiment, other reporting means such as display
tubes and LEDs may be used in place of synthesized voices~
It is a matter of course that the voltage to be
measured in the source voltage monitor 24 can be used
as DC power source for the control system. Since any
trouble such as momentary power failure can be detected
as soon it occurs by virtue of said measurement, the
microcomputer 16 can be forced to reset itself when it
is in normal operation, to thereby prevent the microcomputer
from running away.
INDUSTRIAL APPLICABILITY
As has been described so far, according to the present
invention, in a hea-ting appliance having a digital con-trol
... ..
~2~37
- 23 -
section, there is no possibility of heating being started
by mistake before data on heat-ing is set. Effective
heating data is accepted and the next operation is
reported in synthesized voice, etc., lhe operation is
easy to understand. In the event of a failure, the
normal sequence is prevented from proceeding, so that
there is no possibility of heating being started.
By detecting the opening and closing movement of
~ the door, placement of an object to be heated in the
heating chamber is indirectly ascertained, the time for
such placement being reported to make it sure. On the
basis of these features, safety means can be realized.
Additionally, in a heating appliance which requires
preheating, the procedure for preheating, including
estimation of the time of completion of preheating, is
simple and easy and can be efficienty carried out.
. 3 ;
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