U.S. patent application number 14/329572 was filed with the patent office on 2015-01-22 for method for operating a gas oven and a gas oven.
The applicant listed for this patent is E.G.O. Elektro-Geraetebau GmbH. Invention is credited to Marcus Frank, Rolf Seeburger.
Application Number | 20150020692 14/329572 |
Document ID | / |
Family ID | 51211004 |
Filed Date | 2015-01-22 |
United States Patent
Application |
20150020692 |
Kind Code |
A1 |
Frank; Marcus ; et
al. |
January 22, 2015 |
METHOD FOR OPERATING A GAS OVEN AND A GAS OVEN
Abstract
In the method for operating a gas oven, this has a muffle with a
lower gas burner and with an upper gas burner, wherein for its
control, an electronic control unit is provided for actuating two
gas valves and for igniting the gas burners and also for flame
monitoring. For a combination operation with upper heat and lower
heat in the muffle, the upper gas burner and the lower gas burner
are operated alternately to each other in each case with heating
phases.
Inventors: |
Frank; Marcus;
(Oberderdingen, DE) ; Seeburger; Rolf;
(Oberderdingen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
E.G.O. Elektro-Geraetebau GmbH |
Oberderdingen |
|
DE |
|
|
Family ID: |
51211004 |
Appl. No.: |
14/329572 |
Filed: |
July 11, 2014 |
Current U.S.
Class: |
99/331 ; 431/12;
431/6 |
Current CPC
Class: |
F24C 3/122 20130101;
F24C 3/128 20130101; F24C 3/008 20130101 |
Class at
Publication: |
99/331 ; 431/6;
431/12 |
International
Class: |
F24C 3/12 20060101
F24C003/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 22, 2013 |
DE |
10 2013 214 319.2 |
Claims
1. A method for operating a gas oven, wherein said gas oven has a
muffle with a lower gas burner and with an upper gas burner and
with gas valves for said burners, wherein for controlling said gas
burners, an electronic control unit is provided for actuating said
gas valves and for igniting said gas burners and also for flame
monitoring, wherein for an operating mode with upper heat and lower
heat in said muffle said upper gas burner and said lower gas burner
are operated alternately to each other.
2. The method as claimed in claim 1, wherein temperature
controlling in the gas oven is carried out via an electromechanical
thermostat or via a temperature controller.
3. The method as claimed in claim 1, wherein said upper gas burner
and said lower gas burner are always operated alternately and
always operated consecutively.
4. The method as claimed in claim 3, wherein said upper gas burner
and said lower gas burner are never operated at the same time.
5. The method as claimed in claim 1, wherein between each heating
phase either of said upper gas burner or of said lower gas burner a
pause is provided without operation of a gas burner.
6. The method as claimed in claim 1, wherein during a heating
phase, a changeover is made from one said gas burner to the other
said gas burner after a specified time.
7. The method as claimed in claim 6, wherein said changeover is
made during the heating up of said gas oven or of said muffle with
a short pause without heating between two heating phases of said
gas burners.
8. The method as claimed in claim 1, wherein a thermostat for
temperature control has a cycle time as a thermostat cycle, wherein
in the event that a heating phase of one of said gas burners is
shorter than said cycle time of said thermostat, also after a
heating phase for said heating up during continuous operation of
said gas burner, a changeover of said gas burner is carried out
during said thermostat cycle.
9. The method as claimed in claim 8, wherein said event is during
said heating up of said muffle.
10. The method as claimed in claim 1, wherein a thermostat for
temperature control has a cycle time as a thermostat cycle, wherein
in the event that a heating phase of one of said gas burners is
carried out during said changeover of said gas burner during said
thermostat cycle, a residual time of one of said gas burners, which
residual time remains after an interruption of said thermostat
cycle, is recovered in a next thermostat cycle.
11. The method as claimed in claim 1, wherein during a changeover
of said operating mode of said gas oven from a lower-heat operation
of only said lower gas burner or from an upper-heat operation of
only said upper gas burner to a joint operation of both said gas
burners with changeover between said gas burners, a currently
operated gas burner is further operated up to an end of a cycle or
of a thermostat cycle.
12. The method as claimed in claim 1, wherein during a changeover
of said operating mode of said gas oven from a lower-heat operation
of only said lower gas burner or from an upper-heat operation of
only said upper gas burner to a joint operation of both said gas
burners with changeover between said gas burners, said previously
operated gas burner is immediately shut down and after a certain
delay time said other gas burner is ignited.
13. The method as claimed in claim 1, wherein in an event that a
changeover of said operating mode of said gas oven is carried out
during a pause of said gas burners, the other gas burner than said
last used gas burner is operated during next operation of said
thermostat.
14. A gas oven for implementing said method as claimed in claim 1,
comprising: said gas oven having a muffle in which are arranged an
upper gas burner at the top of said muffle and a lower gas burner
at the bottom of said muffle, and wherein in said muffle also a
temperature sensor is provided for temperature control in said
muffle, wherein said gas oven is provided with an electronic
control unit.
15. A gas oven for implementing said method as claimed in claim 1,
comprising: said gas oven having a muffle in which are arranged an
upper gas burner at the top of said muffle and a lower gas burner
at the bottom of said muffle, and wherein in said muffle also a
temperature sensor is provided for temperature control in said
muffle, wherein said gas oven is provided with a control unit,
which after connection of a corresponding input to a mains
potential activates firing of said corresponding gas burner.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to German Application No.
10 2013 214 319.2, filed Jul. 22, 2013, the contents of which are
hereby incorporated herein in its entirety by reference.
TECHNOLOGICAL FIELD
[0002] The invention relates to a method for operating a gas oven,
and also to a correspondingly designed gas oven.
BACKGROUND
[0003] Electronic control units for gas ovens, which via a spark
plug generate an ignition spark in order to ignite the gas burner,
are known. They can also undertake flame monitoring.
BRIEF SUMMARY
[0004] The invention is based on the object of creating a method
which is referred to in the introduction, and also of creating a
gas oven which is suitable for its implementation, with which
problems of the prior art can be avoided and with which it is
possible in particular to operate a gas oven in a convenient and
diverse manner using a control unit which is not excessively
complicated.
[0005] This object is achieved by means of a method and also by
means of a gas oven. Advantageous and also preferred embodiments of
the invention are the subject of the further claims and are
explained in more detail in the following text. In this case, many
of the features are described only for the method or only for the
gas oven. Regardless of this, however, the features shall to be
able to apply independently both to the method and to the gas oven.
The wording of the claims is rendered by specific reference to the
content of the description.
[0006] The gas oven has a muffle as an inner chamber, in which are
arranged an upper gas burner at the top and a lower gas burner at
the bottom. Furthermore, a thermostat, of known design per se, is
advantageously provided in the muffle for temperature regulation.
The gas oven has any type of electronic control unit, for example
with a DSI (Direct Spark Ignition) system in order to control the
gas burners or their gas valves. With this, one associated gas
valve per gas burner can be activated. Furthermore, the electronic
control unit can be designed for igniting the gas burners,
especially using a spark plug on the gas burner.
[0007] According to the invention, for an operating mode with top
heat and bottom heat, that is to say a so-called combination
operation, the upper gas burner and the lower gas burner in the
muffle are operated alternately to each other, that is to say
operated advantageously with heating phases in each case, and
especially advantageously with pauses on each gas burner between
the heating phases. This means that the upper gas burner and the
lower gas burner are not in operation at the same time since this
could create problems with the combustion conditions in the muffle,
or ignition problems or extinguishing of the flame on the upper gas
burner could occur on account of the lack of fresh air supply and
air vortices on the upper gas burner due to the combustion gases of
the lower gas burner. However, this combination operation with
alternating operation of the upper gas burner and lower gas burner
has the great advantage that heat can be supplied to the food to be
cooked from the top and from the bottom. In particular, in the case
of such a combi-operation an upper heating device is operated in
the manner of a grill, or with the effect as a grill, since food
which is to be cooked is not covered on its upper side in most
cases. As a result of the alternating operation, a desired
temperature for the food to be cooked can be maintained in the
muffle in all cases without any problem, and can be adjusted and
monitored by means of a thermostat or temperature controller. In
this way, it is therefore ensured that a desired temperature
prevails in the muffle for the cooking process. Furthermore, it is
also possible to supply heat to the food to be cooked from the
top--in the manner of an aforesaid grill--in phases and altogether
over a significant time period or up to half the duration of the
overall cooking process.
[0008] Such control units for gas ovens are simply known under the
heading of Direct Spark Ignition. Using these control units,
single-acting or double-acting solenoid valves can be actuated,
wherein the gas valves are advantageously not proportional valves
but designed only for opening and for closing. Consequently, one or
two gas burners in one or two cavities of a gas oven can therefore
be operated with such a DSI. The DSI can open and close the
solenoid valves in order to supply the gas burner with gas.
Furthermore, the DSI advantageously creates an ignition spark, via
a spark plug, at the gas burner for igniting the gas. Also, flame
monitoring can be undertaken by the control unit or by the DSI,
wherein this can be advantageously carried out via an ionization
current measurement. These two last-named functions can also be
undertaken by a differently designed electronic control unit.
[0009] An advantageous electromechanical controller can be a
thermostat. It can be mechanically adjusted to a specific
predetermined temperature and then operated with a known hysteresis
when this predetermined temperature is exceeded or not reached. In
any case, it does not deliver permanent signals which correspond to
the measured temperature but operates at a predetermined
temperature or indicates that the temperature has been exceeded or
not reached. When such a so-called DSI is being used, the use of
such a thermostat is advantageous since it only connects the mains
voltage to the corresponding input of the DSI. When a completely
electronic control unit is being used, in contrast to this, the
temperature in the muffle is measured by means of a thermistor, for
example, and the control unit derives the heating requirement from
the comparison of desired and actual temperatures. The operation
according to the invention is conceivable in both embodiments,
however.
[0010] In an advantageous embodiment of the invention, the upper
gas burner and the lower gas burner are always operated alternately
or always consecutively. This means that after a specific operating
period of the upper gas burner the lower gas burner is operated and
no other, and then the upper gas burner is operated again. This, on
the one hand, can always be carried out consecutively in the manner
of an alternating continuous power generation. Between each heating
phase of one of the gas burners, that is to say either of the upper
gas burner or of the lower gas burner, a pause is alternatively and
advantageously made without operation of one of the gas burners.
When an aforesaid thermostat or an electromechanical thermostat is
being used, this pause can especially serve, for example, for
slowly carrying out the heating up of the muffle, or repeatedly
with short pauses between the heating phases, in order to enable a
more accurate temperature measurement via the thermostat. Also,
after operation of one of the gas burners, the conditions in the
muffle can be normalized and disturbing vortices can also subside
until the other gas burner is then ignited.
[0011] During a heating phase, a changeover from one gas burner to
the other gas burner is advantageously made after a specified time.
This can even be provided during the heating up of the gas oven or
of the muffle. In this case, a short pause can indeed be provided
without heating between two so-called partial heating phases of the
gas burners, but this does not have to be so. As a result of the
alternating operation of the two gas burners even during the
heating up of the muffle, a uniformly distributed heating up is
ensured.
[0012] In one embodiment of the invention, a thermostat for the
temperature control can have a cycle time. In the event that a
heating phase of one of the gas burners, especially during the
heating up of the muffle, is shorter than the cycle time of the
thermostat, a changeover of the gas burner during a thermostat
cycle can also be carried out after a heating phase for the heating
up during continuous operation of the gas burner. Therefore, the
specific conditions here can be taken into account.
[0013] In an advantageous embodiment of the invention, a changeover
of the operating mode of the gas oven from a purely lower-heat
operation using only the lower gas burner or from a purely
upper-heat operation using only the upper gas burner to a joint
operation or combi-operation of both gas burners with a changeover
between the two gas burners can be carried out. In this case, a
currently operated gas burner can be further operated up to the end
of a cycle or of the thermostat cycle before, or possibly after a
short pause, a changeover to the other gas burner is made.
Therefore, the operation of the gas burners, or a heating up, or an
increase of the temperature in the muffle is interrupted as little
as possible.
[0014] Alternatively, during a changeover of the operating mode,
the previously operated gas burner can be shut down immediately, as
explained before for a changeover between the gas burners. The
other gas burner is then ignited either directly or,
advantageously, after a certain delay time. This goes both for a
preceding lower-heat operation and for a preceding upper-heat
operation.
[0015] In one embodiment of the invention, it can be provided that
in the event that a changeover of the operating mode of the gas
oven is carried out during a pause of the gas burners, the other
than the last used gas burner is operated during the next operation
of the thermostat. Therefore, a changeover of the gas burners is
then always carried out again, seen over a longer time.
[0016] The variation of the cycle time is advantageous only up to a
certain point. If in particular a cycle time becomes excessively
long, it can happen that the food to be cooked is heated for a very
long time or even heated for an excessively long time from one side
only and therefore unevenly. This again can be undesirable. This
can especially also occur during a heating-up process.
[0017] As a result of an awkward ratio of cycle time of the
temperature control and cycle time of the changeover operation, it
can also happen that one burner is operated over the desired cycle
time, but the other burner is stopped after several seconds by the
end of the heating cycle. In this case, an inequality between the
two heating modes would arise. This can be met by the interrupted
cycles of the changeover operation being correspondingly continued
or recovered in the respectively next heating cycle of the
temperature control as compensation. Therefore, an arbitrary
distribution of the changeover cycles within the thermostat cycles
can ensue.
[0018] These and additional features, apart from the claims, also
come from the description and the drawings, wherein the individual
features can be realized by themselves in each case or in groups in
the form of a sub-combination in an embodiment of the invention and
in other fields and can represent advantageous and separately
protectable embodiments for which protection is claimed here. The
division of the application into individual sections and
subheadings does not limit the statements which are made under
these in their generality.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0019] Exemplary embodiments of the inventions are represented
schematically in the drawings and are explained in more detail in
the following text. In the drawings:
[0020] FIG. 1 shows a schematic representation of a gas oven,
[0021] FIG. 2 shows the schematic diagram of a gas oven according
to FIG. 1 with a DSI system and
[0022] FIGS. 3 to 11 show different possible changeover operations
of gas burners in the gas oven.
DETAILED DESCRIPTION
[0023] Shown schematically in FIG. 1 is an oven 11 with a muffle 12
in which are arranged an upper gas burner 14 and a lower gas burner
16. The gas burners 14 and 16 are designed as are basically known
in the prior art. The upper gas burner 14 is supplied via a gas
valve 18 and the lower gas burner 16 is supplied via a gas valve
20, wherein the two gas valves can be integrated physically or
constructionally in a sub-assembly. Also, two gas valves can be
connected in series in a burner train in order to fulfill the
requirements for operational safety in the case of malfunction of
one gas valve. The gas valves 18 and 20 are connected to a control
unit 22 of the gas oven 11 which can operate electromechanically or
electronically and is correspondingly designed or consists of one
or more components. Furthermore, provision is additionally made in
the muffle 12 for a temperature sensor which is advantageously
designed as an electromechanical thermostat 24 or thermistor. It is
connected to the control unit 22 and delivers a signal to this in a
known manner.
[0024] Shown in FIG. 2 is a schematic diagram for a gas oven 11
with a DSI system as the control unit. Spark plugs 26 and 28 for
the ignition are shown here on the gas burners 14 and 16. The spark
plugs 26 and 28 are connected to a DSI 34. Thermoelements are not
provided here since flame monitoring is carried out by means of
known ionization current measurement. Furthermore, the gas oven 11
or its control unit 22 additionally has a switch for selecting the
baking mode, a thermostat 24 for temperature control via its
temperature sensor, a timer 36, a door switch 38, an oven lamp 40
and an operating indicator 42.
[0025] In the case of an under-heat operating mode, the output of
the thermostat 24 is connected via the corresponding contact bank
of the selector switch to a so-called heat-request channel of the
DSI 34 which is associated with the lower gas burner 16. If mains
voltage is applied to the heat-request channel then the gas valve
of the corresponding burner is opened and ignition initiated. In
the upper-heat operating mode, the output of the thermostat is
connected to the heat-request channel of the DSI 34 which is
associated with the upper gas burner 14. In the combined operating
mode with upper heat and lower heat, the output of the thermostat
24 is connected to both heat-request channels of the DSI 34. An
alternating operation between the gas burners 14 and 16 is then
carried out, that is to say when both heat-request channels are
energized or engaged at the same time or delayed by only fractions
of a second. In this case, according to the invention only one of
the two gas burners is ignited since both are certainly never to be
operated together. The selection of the gas burner can be carried
out arbitrarily or according to predetermined programming. This can
be seen with reference to FIG. 3, for example.
[0026] In FIG. 3, the temperature in the muffle 12 is plotted on
the vertical axis, specifically at a focal point. Shown in the line
"active burner" is which of the two gas burners 14 or 16 is
operated or is active. The center line stands for upper-heat heat
request and the lowest line stands for lower-heat heat request.
Both indicate the input for the respective gas burner 14 or 16 on
the DSI 34.
[0027] According to FIG. 3, only the upper gas burner 14 for upper
heat OH is operated first of all. For this, it is ignited by the
spark plug 26 and supplied with gas by means of the gas valve 18.
Since the gas valves 18 and 20 are advantageously not generally
proportional valves but only fully open or fully close, the gas
burners can only operate with a fixed, predetermined momentary
output, specifically their full load or rated load. In the
alternative procedure according to FIG. 4, it is to be seen how at
the start it begins with the lower gas burner 16 as lower heat UH,
which is ignited by the spark plug 28 and supplied with gas by
means of the gas valve 20. Which of the two gas burners 14 or 16 is
used first can either be purposefully stored in software in the
control unit 22 or, alternatively, it can be selected randomly.
[0028] From the views of FIGS. 3 and 4, it is to be seen that for a
time only the first started gas burner is active first of all.
Then, it is shut down for a pause, especially if the temperature
has achieved a value--detected by the thermostat 24 and
predetermined by an operating element--corresponding to the wish of
an operator. Then, a phase or pause or break without heating is
carried out, as is generally known in the case of two-step
controllers. After this, an operating phase with heating up of the
muffle 12 is carried out again, but naturally with the other gas
burner.
[0029] From the two lower lines along the X-axis, it is to be seen
that during the operating phases a heat request exists in each case
for both gas burners 14 and 16. The control unit 22 or the DSI 34
then engages the gas burners but in an alternating manner.
[0030] Furthermore, it is known that a clock time or cycle time
t.sub.T,in or t.sub.T,out of the thermostat depends on its
hysteresis, a position of the thermostat sensor in the muffle 12,
the thermal insulation of the oven 11 or of the muffle 12, the heat
output and the predetermined temperature. Therefore, a cycle time
of the thermostat can vary, as is to be seen from FIG. 5 with a
relatively long cycle time. In comparison to this, in FIGS. 3 and 4
short cycle times exist and therefore also less fluctuating of the
temperature. In the case of such long cycle times, there is the
risk, however, that food to be cooked is heated for a relatively
long time on one side only and therefore unevenly. This should be
avoided. This, however, is the case not only in the case of
relatively long cycle times according to FIG. 5 but naturally also
during the heating up, especially if according to FIGS. 3 and 5 the
heating up is started using the upper gas burner 14, or upper heat,
since the risk of burning is especially great in this case.
[0031] In order to avoid such an excessively long, uneven heat
input, in a further embodiment of the invention it can simply be
provided that the gas burners are changed over after a firmly
established or predetermined time. This is shown in FIG. 6 for a
thermostat with a relatively long cycle time. In this case, a start
is made--either in a controlled or arbitrary manner--with one of
the gas burners 14 or 16, this being just with the lower gas burner
16 as lower heat UH in FIG. 6. This is operated for a time
t.sub.UH,in which is stored in the program run of the control unit
22. This can be 30 seconds to 120 seconds, for example. After this,
the lower gas burner 16 is extinguished and a short delay time
t.sub.UH,out follows as a pause. During this time, the atmosphere
in the muffle 12 is normalized so that the upper gas burner 14 can
ignite and be operated without any problem, specifically for a time
t.sub.OH,in. Again, a pause as a delay time t.sub.OH,out follows
this. These four times are selected according to the conditions in
the gas oven 11 or in the muffle 12 and according to a desired
ratio between upper heat OH and lower heat UH. In the case the time
t.sub.UH,in is shorter than the cycle time t.sub.T,in of the
thermostat, as is shown in FIG. 6, a changeover of the gas burners
is carried out not only during the heating up but also in the
steady state. This is simply to be seen in FIG. 6 with a changeover
from the lower gas burner 16 to the upper gas burner 14 during the
cycle time t.sub.T,in. This is therefore a relatively longer
thermostat cycle than previously described. If, however, the time
t.sub.UH,in or the time t.sub.OH,in is greater than the cycle time
t.sub.T,in, then no changeover is carried out within a thermostat
cycle but only at the next cycle. This is to be seen in FIG. 7, in
which after the heating-up phase only one of the two burners 14 or
16 is operated in each case during a relatively short thermostat
cycle t.sub.T,in.
[0032] Alternatively, it is also possible, however, that a
changeover cycle of a gas burner, which has been interrupted by the
cycle of the thermostat before its end, is recovered in the next
cycle. Therefore, an arbitrary distribution of the changeover
cycles within the thermostat cycles ensues--see FIG. 11.
[0033] Shown in FIG. 8 is how a changeover of the operating mode of
the gas oven 11 is carried out. At the beginning, a lower heat
operation using only the lower gas burner 16 exists. If, during a
cycle time t.sub.T,in, a changeover is made from the lower-heat
operating mode to a combination operation at a time point which is
vertically drawn in by a dashed line, then in a first alternative
the currently operated burner can be further operated up to the end
of the cycle. In FIG. 8, it is to be seen in particular that during
the second engagement of the lower gas burner 16 a heat request for
upper heat OH already exists. Alternatively, it is also possible
that the previously operated gas burner--in this case the lower gas
burner 16--is immediately shut down. The other gas burner--in this
case the upper gas burner 14--can then be ignited after a delay
time or pause for stabilizing the conditions in the muffle 12. This
is to be seen in FIG. 9.
[0034] If a changeover between the gas burners 14 and 16 is carried
out during the time t.sub.T,out, then with the next operation of
the thermostat not the last used, but the other, gas burner is
operated. This is to be clearly seen in FIG. 10 at the time point
of the vertical dashed line. After this, a heat request for the
upper heat OH then exists and the upper gas burner 14 is directly
operated or fired as the active burner.
[0035] In a once more further development stage of the invention,
it is also conceivable that during the program run, t.sub.T,in and
t.sub.T,out are measured and from this the optimum values for the
other four described times are calculated. Furthermore, in the best
case the times t.sub.OH,out and t.sub.UH,in are even close to zero
so as not to interrupt a heat supply for an unnecessarily long
time.
[0036] If instead of the electromechanical thermostat together
along with a thermostat sensor 24 an electronic control unit is
used, that is to say without DSI, with a temperature-dependent
resistance as a temperature sensor, it is possible to continuously
access measured values of the temperature sensor. As in the case of
a DSI, there is no dependency upon "in" or "out" signals which the
thermomechanical thermostat delivers.
* * * * *