DE102007054340A1 - Cooking device for cooking food, has mesoporous filter made of material consisting of silicon oxide and/or silicate for selectively filtering gaseous silicon connections from sample gas of space atmosphere using filter - Google Patents

Abstract

The device (1) has a cooking chamber (3) closable by a door (15) or cover and accommodating cooking goods (6). A heating device (27) has a gas sensor (30) staying in effective connection with the chamber for determining chemical conditions of chamber atmosphere, and a filter device attached to the chamber and sensor. The filter device has a mesoporous filter (39) with middle pore radius in the range of 1-50 nanometer. The filter is made of material having silicon oxide and/or silicate for selectively filtering gaseous silicon connections from sample gas of space atmosphere using the filter.

Description

The The invention relates to a cooking appliance comprising an over a door or a lid closable cooking space, can be introduced into the food, a heater at least one with the cooking chamber operatively connected gas sensor for determination the chemical state of the cooking chamber atmosphere and a between the cooking chamber and the gas sensor attached filter device, cooking appliances for large and commercial kitchens, with sensors are equipped to control cooking processes are in the state of Technique known. To avoid the use of puncture probes, different devices and methods are described, with which the condition of a food is determined without contact can be.

A generic cooking appliance with a gas sensor and a sampling system is z. B. in the WO 2006/069563 A1 described. There it is proposed to equip the leads to the gas sensor with a filter which serves to separate the cooking chamber to be measured atmosphere of solid particles and fat and liquid drops.

In such a cooking device usually seals or the like of silicone elastomers, that is used with organic silicon compounds. As these seals become warm during cooking operation, volatile organic silicon compounds are released from them. These pass through the supply lines to the gas sensor. When the organic silicon compounds deposit on the surface of the gas sensor, which is usually a semiconductor gas sensor, they oxidize there, so that a silicon oxide layer is formed on the surface of the semiconductor gas sensor, which increasingly passivates the gas sensor. A disadvantage of the in the WO 2006/069563 A1 The structure described is thus that the sensitivity of the gas sensor is reduced over time by the resulting in the cooking appliance volatile organic silicon compounds and the same is ultimately useless.

From the EP 0 940 680 B1 For example, a gas sensor for bridge circuits is known which comprises a catalytic detector element with an opening. A filter material is positioned between the opening and the detector element or in the opening. The material used is a bronze sinter with a pore size of 9 to 50 μm. The material should at least partially filter out hydrogen sulfide from the gas to be analyzed in order to protect the gas sensor from the harmful effects of this gas. However, such a filter is not suitable for filtering out the harmful organic silicon compounds that may arise during the operation of a cooking appliance.

From the JP 2002 052 338 For example, a silicon gas absorber is known that filters out silicon gases from gases to be detected. In this case, a powder or fiber material is used which comprises silica gel or activated carbon as the main component. Such filter materials must be replaced regularly and are therefore only conditionally suitable for use in cooking appliances. In addition, the gases to be measured would be filtered out in such an application, so that disadvantages for the measurement of the gas sensor are to be expected.

The JP 2004 020 377 discloses a catalytic gas sensor with a filter formed as a silicon trap. The filter is made of a material that can be poisoned by the silicon. Thus, the catalytic gas sensor itself is to be protected from poisoning by a silicon compound. The sintered metal oxide-based filter, however, has the disadvantage that it is passivated by the addition of silicon oxide over time. In addition, an improvement in the efficiency in general would be desirable.

From the US 6,365,108 B1 is a siloxane filter system is known, with which an oxygen sensor for the control of an internal combustion engine is protected. The filter used here is a fiber filter through which the siloxane-containing gas flows. However, the proposed as a material for the fiber filter stainless steel is not well suited for filtering organic silicon compounds.

A Mikrogasanalysesystem with a heatable filter is from the DE 102 45 947 A1 known. In this case, the so-called "silicone on insulater waver" is used as the filter, whereby the filtering takes place via the surface of the wafer layer.With the relatively small surface of the wafer layer, only relatively little gas can be cleaned, so that the use of such a filter in the field of cooking appliance technology is not appropriate.

The DE 103 52 390 A1 discloses a gas detector with a porous film intended to keep water, oil and / or dust away from a gas sensor. As a material for the filter, a film of PTFE (polytetrafluoroethylene) having a pore diameter of 1 μm is proposed. This filter is not suitable for filtering organic silicon compounds.

The JP 2004 261 672 discloses a selective gasoline absorption filter made of a porous silica. The material has mesopores with a diameter between 1 and 50 nm. Furthermore, on the wall surfaces micropores with a pore diameter between 0.2 and 0.8 nm. This is to improve the analysis of a gas. However, this filter is not for the protection of a gas sensor and is not intended to filter out organic silicon compounds from a gas to be measured.

The JP 2004 045 324 discloses a gas filter for removing organic silicon gases from a gas mixture. For this purpose, permeable porous layers are used which consist of heat-resistant fibers and powders. By silica components or aluminosilicates, the organic silicon gases can be adsorbed in the filter and thus separated from the remaining gas. Since the filter contains platinum powder, it is relatively expensive to manufacture. In addition, its effectiveness is low.

From the DE 195 17 144 C1 a filter for an electrochemical measuring cell is known, which consists of porous gas-permeable material. The material used here is polytetrafluoroethylene (PTFE). To build the filter itself, a silicone gasket is used. Such a filter would thus in a hot gas stream from a cooking space itself release volatile organic silicon compounds and is therefore unsuitable for use in proofers.

From the WO 97/38776 A1 a fused filter membrane device is provided with which a purified sample gas for a gas analyzer can be generated. For this purpose, porous membranes are used which separate a gas stream from solid and liquid particles. The device thus serves only to separate a sample gas from solid and liquid particles and is not suitable for filtering organic silicon compounds.

The known filter systems are therefore for a variety of reasons not suitable, volatile organic silicon compound effectively filter out of a cooking chamber from a hot gas. Filter systems made of organic compounds usually do not have the necessary heat resistance, in order for a use in a cooking appliance in question. membranes, Filters made of fibers or filters with coarse pores do not have sufficient Reaction surfaces around the organic to be filtered out Silicon compounds with the necessary efficiency from the sample gas to remove. Other filters, such as. B. Activated carbon filters are not selective enough, as they also remove other components from the gases would.

Of the The invention is therefore based on the object, the generic Further develop cooking appliance such that the disadvantages overcome in the prior art. Especially is to filter passivating organic silicon compounds be selective and effective, but without other organic compounds withhold the filtering at the same time both low maintenance and heat resistant should be.

These The object is achieved according to the invention that the filter device at least one mesoporous Comprises filters having a mean pore radius between 1 nm and 50 nm, the material of the filter comprises silica and / or silicate, to selectively with the filter gaseous silicon compounds to filter from a sample gas of the cooking chamber atmosphere.

It is preferred that the material of the filter consists of silicon oxide and / or silicate and / or the filter has mesopores with an average pore radius of approximately 10 nm, and / or the specific surface area of the filter is approximately 1000 m ² / g.

With The invention also proposes that the filter be detachable, in particular in a housing, is mounted, preferably the housing on a wall bounding the cooking chamber in the area an opening in said wall, preferably detachable, attachable.

there it can be provided that the gas sensor, in particular detachable, at least partially disposed in the housing, preferably opposite the opening.

With The invention further proposes that the filter is installed in a net and / or a gauze, preferably the net and / or the gauze on the housing, in particular detachable, attached.

there can be provided that the network and / or gauze off Polytetrafluoroethylene (PTFE) and / or stainless steel is or exists.

With The invention is also proposed that the housing at least on its contact with Garraumatmosphäre in contact Surfaces made of stainless steel and preferably in shape a stainless steel cylinder is formed.

Farther It is proposed that the filter device additionally a coarse filter disposed between the filter and the Cooking chamber is arranged to the filter and the gas sensor from particles, such as Solids, fat and / or liquid droplets, too protect, wherein the coarse filter is preferably made of stainless steel is formed and / or releasably attached to the housing and / or the cooking chamber wall mounted in the region of the opening is.

Cooking devices according to the invention can also be characterized by at least one pump and / or blower device that supplies at least the gas sensor cooking chamber atmosphere.

there it can be provided that the pump and / or blower device the cooking chamber at least partially through the filter leads before it reaches the gas sensor.

Prefers Furthermore, a control or regulating device is in operative connection with the heating device, the gas sensor, the filter device, the pump and / or Gebläseeinrich device, a Garraumatmosphärenkirkulationseinrichtung, an operating device and / or a display device is provided.

moreover Can at least one seal between the door or the Lid and the cooking chamber and / or at least one Kabelumhüllung comprising organic silicon compounds, in particular silicone elastomers, be provided.

After all is also proposed with the invention that the gas sensor comprises at least one semiconductor gas sensor, and / or the conductivity of the gas sensor detectable and on the display device, in particular as a function of time, displayable is.

Of the Invention is therefore based on the surprising finding that the volatile organic silicon compounds, which arise during the operation of a cooking appliance, effective with a mesoporous silica filter or a mesoporous filter based on silicate from the cooking chamber atmosphere can be filtered out, the a gas sensor for Determination of the chemical state of the cooking chamber atmosphere and thus a Garegrads a Garguts supplied in the oven becomes. Other organic constituents that escape from the food are not stopped by the mesoporous silica filter. As a result, the measurements of the gas sensor are not distorted, by other volatile components of the cooking chamber atmosphere, for determining the chemical state of the cooking chamber atmosphere and thus of the food are important, removed or reduced.

The Use of silica is not just for the tall ones Temperatures that occur in cooking appliances, suitable, but also advantageous because the volatile silicon compounds oxidized at the surfaces of the filter to silica and thus the surface of the filter also in the long term is not passivated by the filtering. The mesopores put while making sure that the filter has a large surface area but at the same time the pores are large enough are to be measured with the gas sensor organic compounds pass therethrough. By the cooking appliance according to the invention it is ensured that a lane that forms part of the Cooking device, not by those occurring in the cooking appliance organic silicon compounds is impaired.

Further Features and advantages of the invention will become apparent from the following Description of an embodiment of a cooking appliance according to the invention on the basis of schematic drawings. Showing:

1 the structure of a cooking appliance according to the invention in a sectional view,

2 the sensitivity of two gas sensors in a cooking appliance without filters and against poisoning with organic silicon compounds, in the form of their conductivity as a function of time, and

3 the sensitivity of the two gas sensors in a cooking appliance with and without filters and before and after a poisoning with organic silicon compounds, again in the form of their conductivity as a function of time.

1 shows the schematic structure of a cooking appliance according to the invention 1 with a cooking space 3 in which a food is 6 on a food support 9 is placed. The cooking space 3 is on all sides by furnace walls 12 limited. On one side of the cooking chamber 3 is one through a door 15 closable opening provided. Between the door 15 and the furnace walls 12 is a seal 18 attached, which is a tight closing of the cooking chamber 3 through the door 15 allows.

During operation of the cooking appliance 1 with the door closed 15 is the air in the cooking chamber 3 with the help of a fan 21 behind a baffle 24 attached, circulated. With the help of a heater 27 that the fan wheel 21 Surrounds the atmosphere in the oven 3 be heated. The heat is transferred through the fan 21 circulated air on the food 6 , With increasing heating of the food 6 also change the by the food 6 released organic substances that accumulate in the cooking chamber atmosphere.

These substances are combined with a gas sensor 30 measured. At the gas sensor 30 it is usually a semiconductor gas sensor that is housed in a housing 33 is attached and over an opening 36 with the cooking space 3 of the cooking appliance 1 connected is. By means of a pump (not shown), the gas sensor 30 Atmosphere from the oven 3 be supplied. The by the food 6 released substances can thus from the gas sensor 30 be measured.

In addition to the food 6 but also the seal 18 the door 15 heated. The seal 18 must therefore be made of a temperature-resistant material, which should have in addition to the temperature resistance but also flexible properties such as rubber. Silicone elastomers as well as other organic silicon compounds are particularly suitable as material for such applications. In addition to the seal 18 can in the oven 3 even more components with organic silicon compounds may be present. An example of this is a core temperature probe (not shown) constructed via a flexible cable having an outer jacket containing organic silicon compounds. Due to the circulated cooking chamber atmosphere, the food to be cooked 6 , the seal 18 and other components heated. When these materials are heated, volatile organic silicon compounds are formed, which accumulate in the cooking chamber atmosphere. These organic silicon compounds also reach the gas sensor via the cooking chamber atmosphere 30 , An example of such a silicon compound is z. For example hexamethyldisiloxane. These compounds settle on the surface of the gas sensor 30 and are oxidized there. In semiconductor gas sensors, the volatile silicon compounds decompose on the hot sensor surface and form silicon oxide there. This covers the sensitive layer of the gas sensor 30 and thus worsens the sensor properties, up to a complete destruction of the gas sensor 30 , Since all soft materials, such. B. the door seal 18 of the cooking chamber 3 , Made of such silicone elastomers, from which escape the volatile silicon compounds when heated, this places a significant burden on the gas sensor 30 Silicone elastomers are preferred in cooking appliances because they are both heat resistant and food safe.

To the volatile silicon compounds of the gas sensor 30 fed Probegas from the oven 3 to disconnect is in the case 33 a mesoporous silica filter 39 built-in. The filter 39 This is done between two stainless steel gazes or nets 42 accommodated. Alternatively, such a network 42 but also made of PTFE. In cooking appliance technology, however, it has proven itself, components, with the cooking chamber 3 to be made of stainless steel. Accordingly, the housing is 33 preferably a stainless steel cylinder.

The filter 39 is like that on the stove wall 12 of the cooking chamber 3 attached so that the gases from the oven 3 first through the filter 39 through before they become the gas sensor 30 reach. The filter material consists of mesoporous silica with a pore radius of approximately 10 nm. The filter material selectively filters out the volatile silicon compounds and allows the target gases out of the cooking chamber 3 to the gas sensor 30 happen. The volatile silicon compounds settle on the surfaces of the mesopores of the silicon dioxide filter and are oxidized there. As a result, new silicon oxide compounds are formed on the surface of the pores, so that the filter itself is not passivated. Clogging of the pores can only be expected after a very long time. In addition, the silicon dioxide is completely insensitive to the temperatures of the gases from the cooking chamber. This is how it succeeds, the gas sensor 30 to protect against poisoning by the volatile silicon compounds.

The 2 and 3 show measurements of conductances of two gas sensors, which on a furnace wall of a cooking chamber of a cooking appliance (similar 1 ) are mounted. The gas sensors are mounted in operative connection with the cooking chamber so that they can detect gas from the oven. During the measurements, a defined amount of octanal was introduced into the oven after about 4 minutes (240 seconds). Octanal is a typical target gas, which is also produced when cooking meat. After approximately 14 minutes (820 seconds), the supply of octanal was stopped. The beginning and end of Octanalzufuhr is in the 2 and 3 with the dashed lines A (beginning of Octanalzufuhr) and B (end of Octanalzufuhr).

2 shows the measurement of two gas sensors, which were connected without the interposition of a filter to the cooking chamber of the cooking appliance. The individual measuring points of the first sensor are shown with squares, the measurements of the second sensor with circles. The measurements show that both sensors react identically without filters and without poisoning by organic silicon compounds. It can be clearly seen how the conductivity of the two semiconductor gas sensors increases when octanal is added to the cooking chamber atmosphere.

3 shows in each case a series of measurements with the two sensors before and after a poisoning by organic silicon compounds. The first sensor was equipped with a filter (measuring points denoted by squares and triangles with tip above) and the second sensor without filter (measuring points indicated by circles and triangles with tip pointing downwards). The measurements after poisoning by organic silicon compounds are in 3 marked by triangles. In order to accelerate the poisoning process, which is normally very slow, a gasket has been placed in the cooking chamber of a cooking appliance, in which a great deal of organic silicon compounds have been released. The conductivity of the sensors is a measure of their Reaktionsfä ability. It can be seen that before the poisoning the sensor without filter (measuring points with circles) has a slightly higher sensitivity than the sensor with filter (measuring points with squares). This results from the fact that the filter inhibits the target gases and thus slightly reduces the sensitivity of the sensor system. After the poisoning one sees clearly that the sensor reacts only very weakly to the Octanal without filter (measuring points with triangles, point downwards). The response of the sensor with filter, however, is virtually unchanged (measuring points with triangles, top tip). This shows that the sensor with a mesoporous silica filter can be very well protected from the harmful effects of volatile organic silicon compounds.

The mesopores (mesopore radius 1 to 50 nm) cause a very high specific surface area (up to about 1000 m ² per gram) of the silicon oxide. Silicon oxide filters out the volatile silicon compounds with high selectivity and allows the compounds to be detected to pass through to a high degree. This makes it possible to filter out particularly large amounts of volatile silicon compounds without severely impairing the diffusion time of the target gases.

The in the foregoing description, the drawings and the claims disclosed features of the invention can both individually as well as in any combination for realization the invention in its various embodiments be essential.

1

Cooking appliance

3

oven

6

be cooked

9

food support

12

furnace wall

15

door

18

poetry

21

fan

24

Air baffle

27

heater

30

gas sensor

33

casing

36

opening

39

filter

42

Gauze / Network

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - WO 2006/069563 A1 [0002, 0003]
• - EP 0940680 B1 [0004]
• - JP 2002052338 [0005]
• - JP 2004020377 [0006]
• - US 6365108 B1 [0007]
• DE 10245947 A1 [0008]
• - DE 10352390 A1 [0009]
• - JP 2004261672 [0010]
• - JP 2004045324 [0011]
• - DE 19517144 C1 [0012]
• WO 97/38776 A1 [0013]

Claims (13)

Cooking appliance ( 1 ), comprising one over a door ( 15 ) or a lid closable cooking space ( 3 ), into the food ( 6 ), a heating device ( 27 ) at least one with the cooking space ( 3 ) operatively connected gas sensor ( 30 ) for determining the chemical state of the cooking chamber and one between the cooking chamber ( 3 ) and the gas sensor ( 30 ), characterized in that the filter device comprises at least one mesoporous filter ( 39 ) with an average pore radius between 1 nm and 50 nm, the material of the filter ( 39 ) Silica and / or silicate to react with the filter ( 39 ) to selectively filter gaseous silicon compounds from a sample gas of the cooking chamber atmosphere. Cooking appliance according to claim 1, characterized in that the material of the filter ( 39 ) consists of Sicilium oxide and / or silicate and / or the filter ( 39 ) Mesopores having an average pore radius of about 10 nm, and / or the specific surface area of the filter ( 39 ) is about 1000 m ² / g. Cooking appliance according to claim 1 or 2, characterized in that the filter ( 39 ) detachable, in particular in a housing ( 33 ), wherein preferably the housing ( 33 ) at one of the cooking chamber ( 3 ) bounding wall ( 12 ) in the region of an opening ( 36 ) in said wall ( 12 ), preferably releasably attachable. Cooking appliance according to claim 3, characterized in that the gas sensor ( 30 ), in particular detachably, at least partially in the housing ( 33 ) is arranged, preferably the opening ( 36 ) opposite. Cooking appliance according to one of the preceding claims, characterized in that the filter ( 39 ) in a net and / or gauze ( 42 ), wherein preferably the net and / or the gauze ( 42 ) on the housing ( 33 ), in particular detachably, is attached. Cooking appliance according to claim 5, characterized in that the net and / or the gauze ( 42 ) consists of polytetrafluoroethylene (PTFE) and / or stainless steel or exist. Cooking appliance according to one of claims 3 to 6, characterized in that the housing ( 33 ) is made of stainless steel at least on its contactable with Garraumatmosphäre surfaces and is preferably formed in the form of a stainless steel cylinder. Cooking appliance according to one of the preceding claims, characterized in that the filter device additionally comprises a coarse filter which is located between the filter ( 39 ) and the cooking chamber ( 3 ) is arranged around the filter ( 39 ) and the gas sensor ( 30 ) from particles, such as solids, fat and / or liquid droplets to protect, wherein the coarse filter is preferably made of stainless steel and / or releasably attached to the housing ( 33 ) and / or the cooking chamber wall ( 12 ) in the region of the opening ( 36 ) is attached. Cooking appliance according to one of the preceding claims, characterized by at least one pump and / or blower device which at least the gas sensor ( 30 ) Supplies cooking chamber atmosphere. Cooking appliance according to claim 9, characterized in that the pumping and / or blowing device at least partially through the filter ( 39 ) before it becomes a gas sensor ( 30 ). Cooking appliance according to one of the preceding claims, characterized by a control or regulating device in operative connection with the heating device ( 27 ), the gas sensor ( 30 ), the filter device ( 39 ), the pumping and / or blowing device, a cooking chamber atmosphere circulation device ( 21 ), an operating device and / or a display device. Cooking appliance according to one of the preceding claims, characterized by at least one seal ( 18 ) between the door ( 15 ) or the lid and the cooking chamber ( 3 ) and / or at least one cable sheath comprising organic silicon compounds, in particular silicone elastomers. Cooking appliance according to one of the preceding claims, characterized in that the gas sensor ( 30 ) comprises at least one semiconductor gas sensor, and / or the conductivity of the gas sensor ( 30 ) can be detected and on the display device, in particular as a function of time, can be displayed.