DE102004011390B3 - Cooking vessel`s pressure regulating method, involves controlling heating device after completing specified heating period based on parameter of pulse width modulation, and difference between data detected in vessel and reference pressure - Google Patents

Abstract

The method involves activating a heating device with a preset amount of heat, and detecting pressure data in a cooking vessel. Heating duration for the given amount of heat is determined to obtain reference pressure. A parameter of pulse width modulation is found from the heat applied to the device. The device is controlled after completing specified heating period based on the parameter and difference between the data and pressure. An independent claim is also included for a cooking vessel for carrying out a pressure regulation method in a kitchen.

Description

The The invention relates to a method for controlling a pressure within a substantially pressure-tight closable and heated by a heater Cooking space to at least a certain target pressure; and a cooking appliance for performing such a procedure.

Pressure control methods are well known in the art, such as from the GB 2 027 612 A , Nevertheless, there is still the need to further develop the pressure control to reduce costs and improve cooking results.

Food can cooked in different ways by temperature influences become. Increasingly, a pressure cooking and steam pressure cooking is used. When steam cooking is the exact knowledge of the amount of water vapor, especially saturated Steam, necessary in the cooking chamber. A generated by heat supply water vapor pressure within the cooking chamber can be assign a specific temperature within the cooking chamber.

From the DE 197 00 602 A1 a Druckgargefäß is known in which the heating power of a heater is controlled by means of a heating control, using a Statemeßgliedes for generating a Garprozeßzustand, in particular a temperature and / or pressure actual value, representing state signal, and an electronic monitoring device for generating a from the time-varying state signal and a fixed or variable cooking time setpoint dependent monitoring signal for the heating control.

The DE 37 02 975 A1 discloses the determination of a heat capacity of a filling amount in a pressure cooker by means of a time measurement during the heating of the pressure cooker.

In the DE 197 11 291 A1 a method for controlling thermal paths and heaters is described in household appliances, take place in the three phases, namely in the form of a start of a setpoint, a transient to a desired value and holding the setpoint, the control during the control process for the object to be heated without Over and undershoot should occur.

Out US 2002/0139253 A1 is a connectionless steam generator with an automatic electric steam trap known.

task The invention is a method for controlling a pressure within a substantially pressure-tight closable and heated by a heater Garraums on at least a certain target pressure to deliver at the pressure as simple as possible and can be controlled quickly to the target pressure. This regulation should also for low water quantities the cooking space work reliably.

These The object is achieved by a method according to claim 1.

preferred embodiments the method according to the invention are in the claims 2 to 12 described.

Further With the invention, a cooking appliance for performing a inventive method delivered according to claim 13.

preferred Cooking devices according to the invention are in the claims 14 to 16 described.

Further Features and advantages of the invention will become apparent from the following Description, in the preferred embodiments thereof based are explained by schematic drawings. Showing:

1 an inventive cooking appliance in side view;

2 Vapor pressure curves over the temperature;

3 Pressure curves over time with the same heat output and different water quantities; and

4a + 4b Curves of the pressure in a method according to the invention over time at a water fill.

An inventive cooking appliance 1 includes according to 1 a crucible 2 that has a lid 3 is closable. Between the crucible 2 and the lid 3 is at least one element of density 4 arranged to the one of the crucible 2 and the lid 3 limited cooking space pressure-tight lockable design. The inside of the crucible 2 and thus the cooking space is over three heating elements 5 heatable. The pressure in the cooking chamber is via a pressure sensor 6 detectable by the lid 3 through is in operative connection with the cooking chamber. About the lid 3 There is also a pressure relief valve 7 as well as a print drain valve 8th in operative connection with the cooking space. A control unit 9 stands with the three heating elements 5 , the pressure sensor 6 and a storage unit 10 in active connection.

Depending on the structure of the cooking appliance 1 a desired pressure is determined at which an optimized Druckgarvorgang can be performed in the cooking appliance. In the present example, the target pressure should be 150 mbar.

It is important for a proper execution of Druckgarvorgangs that the so-called wet steam, so not fully saturated water vapor, escaped from the cooking chamber before Druckgaren, so that during the Druckgarprozeß essentially exclusively saturated steam in the cooking chamber, which is a high ensures efficient heat transfer to not shown food. An increase in the pressure in the cooking chamber causes an increase in the boiling point of the water in the oven, as well as from the vapor pressure curves according to 2 results. An increased boiling temperature leads to accelerated cooking. To maintain a certain pressure in the filled with saturated steam cooking space is therefore the maintenance of a certain temperature in the cooking space requirement. Thus, if a target pressure is reached in a printing process, it is only necessary to receive the same over the housing of the crucible in order to obtain the same 2 and the lid 3 outgoing heat loss can be compensated. In other words, a constant heat inflow then ensures the maintenance of a constant pressure.

Before carrying out a pressure control method according to the invention, empirical values must be obtained and stored in the memory unit 10 be filed. This is the crucible 2 filled with water at a predefined level and then over the lid 3 locked.

The filled water is then heated to boiling with the pressure relief valve open 8th , As soon as the steam in the cooking chamber is substantially saturated, the pressure relief valve 8th closed. Subsequently, the heating elements 5 via the control unit 9 energized while the output data of the pressure sensor 6 be detected. This process is repeated for different levels, for example for 5, 30, 60 and 90 liters of water in the crucible 2 so that the in 3 taken curves shown and in the memory unit 10 can be stored on the later, for pressure control as empirical values, can be used.

Following the recording of the in 3 shown curves can take place a steam pressure cooking. For this purpose, a certain amount of water and a food (not shown) in the crucible 2 brought in. Subsequently, five phases are run through with reference to 4a be explained in more detail.

Phase 1

At the beginning, the heating elements 5 switched on, while they remain switched on until a slight overpressure of about 25 mbar is set in the oven. This pressure is maintained until only partially saturated steam from the cooking chamber via the pressure relief valve 8th has escaped, so that only substantially saturated water vapor remains in the cooking chamber. This takes about 120 seconds.

Phase 2

The pressure relief valve 8th as well as the pressure relief valve 7 are closed, and the heating elements 5 are on. From the output values of the pressure sensor 6 the pressure increase is detected as a function of time. Performing a comparison of the pressure values detected to increase pressure with those in the storage unit 10 stored experience values and the target pressure are all other parameters of the pressure control be true. More precisely, the amount of water in the cooking chamber is first determined by the comparison. From this, in particular, the heating time is determined until the desired pressure is reached for a given heat output.

Phase 3

The heating elements 5 remain switched on until the end of the heating period determined in phase 2.

Phase 4

After the end of the heating period determined in phase 2, the heating elements become 5 is switched off, and over a period of time, which has been determined as another parameter in phase 2, a lag of the pressure is awaited.

Phase 5

In phase 5, a control algorithm is started, in which essentially the heating elements 5 a heat flow for regulating the pressure in the cooking chamber is applied to the desired pressure, on the basis of a pulse width modulation. This pulse width modulation leads to an optimization of the heat flow and is described below with reference to 4b described.

During phase 2, the parameters of the pulse width modulation are also predetermined, and in particular the turn-on time and the cycle time of the same. Likewise, an upper pressure limit and a lower pressure limit are determined, for example in the order of 3 mbar above or below the desired pressure. The pulse width modulation basically runs as follows:
The heating elements 5 are turned on when the detected pressure falls below the target pressure, wherein the supplied heat flow is varied via the pulse width modulation is supplied, and until the detected pressure reaches the desired pressure again. Then the heating elements 5 switched off. This is repeated as long as the control is to be maintained at the desired pressure.

However, if the detected pressure exceeds the upper pressure limit, for example by 5 mbar, as in 4b After approximately 5 seconds, the predetermined switch-on time of the pulse width modulation is reduced in proportion to this excess. The same applies to falling below the lower pressure limit. This transient phase is followed by the regulation described above after about 30 seconds.

With the pressure control method according to the invention can be in a cooking appliance according to 1 in a particularly simple, inexpensive and yet accurate way the pressure inside a cooking chamber to achieve optimum cooking results.

1

Cooking appliance

2

crucible

3

cover

4

sealing element

5

heating element

6

pressure sensor

7

Pressure relief valve

8th

Pressure release valve

9

control unit

10

storage unit

Claims (16)

Method for regulating a pressure within a substantially pressure-tight closable and heated by a heater Cooking chamber on at least a certain target pressure, comprising the following Steps: a) switching on the heater with a predetermined Heating capacity, b) detecting pressure data within the cooking chamber, comprising the step response of the pressure on the heating and the essentially pressure-tight closing of the cooking chamber, c) Determine at least one heating period at the given heating power for Reaching the target pressure and at least one parameter of a pulse width modulation from a heating power to be applied to the heater or of heating currents to be applied to the heater, including the on-time and / or the clock duration of the pulse width modulation, by comparison detected Print data with empirical values under evaluation of the step response the pressure and detecting a difference between detected pressure data and the target pressure, and d) operating the heater until to the end of the specific heating time with the specified heating power, and e) control of the heater after the expiration of certain Heating duration in a control phase based on a pulse width modulation by switching the heating device on or off in dependence from the difference between detected Pressure data and the target pressure and the predetermined parameter for the Pulse width modulation. Method according to claim 1, characterized in that that the Target pressure, preferably before step a), predetermined and / or is determined, in particular depending on the structure of the Cooking chamber, wherein the target pressure preferably between 100 and 200 mbar, most preferably about 150 mbar. Method according to claim 1 or 2, characterized that the Experience values stored in a memory unit as tables and / or curves are. Method according to one of the preceding claims, characterized characterized in that Recording the experience of the cooking chamber open and at least one filled with a certain amount of water will, then the cooking space over the heater is heated until the water vapor essentially saturated in the cooking chamber is, and then the cooking chamber substantially pressure sealed becomes. Method according to claim 4, characterized in that that for at least four different amounts of water in the cooking chamber respectively the course the pressure within a substantially pressure-sealed Cooking chamber at least one specific heating power of the heater at least about a certain period of time is measured, and from these courses the Experiences are gained, in particular by selecting representative curves or averaged curves. Method according to one of the preceding claims, characterized in that the step response within a time window, in particular over empirical values, preferably of up to 10 seconds, in particular calculated from substantially pressure-tight closing of the cooking chamber and applying the heating power to the heater, detected and compared with empirical values, wherein an additional comparison with the target pressure is preferably carried out. Method according to one of the preceding claims, characterized characterized in that Step c) comprises a determination of the amount of water in the oven. Method according to one of the preceding claims, characterized characterized in that Step c) a period of time between the time of turning off the heater at the end of the specified heating period in the step d.1) until the heater is switched on in step d.2), in particular by evaluating the step response of the Pressure, preferably based on the desired pressure and / or empirical values, is determined. Method according to one of the preceding claims, characterized characterized in that Parameters of the pulse width modulation with determination of the amount of water is determined in the oven. Method according to one of the preceding claims, characterized characterized in that a upper pressure limit and lower pressure limit specified or determined particular, by comparing recorded pressure data with empirical values, preferably in step c), in particular with determination of the amount of water in the oven. Method according to one of the preceding claims, characterized characterized in that Step e) the heater is turned off as soon as the detected pressure exceeds the set pressure, and the heater is turned on as soon as the detected pressure the target pressure falls below the simultaneous initiation of the Pulse width modulation. Method according to claim 11, characterized in that that when exceeded the upper pressure limit by the detected pressure, the switch-on for the Pulse width modulation reduced proportionally to the excess is, and falls below the lower pressure limit by the detected pressure the switch-on of the pulse width modulation, in particular proportionally to undershoot, elevated becomes. Cooking appliance ( 1 ) with a cooking chamber, which has a heating device ( 5 ) and at least one shut-off device ( 7 . 8th ) is substantially pressure-tight manner, with at least one pressure sensor ( 6 ) for detecting the pressure within the cooking chamber and with a control and / or control unit ( 9 ) in operative connection with the pressure sensor ( 6 ) and the heater ( 5 ), characterized in that via the control and / or regulating device ( 9 ) a method according to any one of the preceding claims is feasible. Cooking appliance according to claim 13, characterized in that the control and / or regulating device ( 9 ) to a storage unit ( 10 ), wherein empirical values, representatives of empirical values and / or mean values of empirical values can be stored in the memory unit, which is preferably encompassed by the control and / or regulating device. Cooking appliance according to claim 13 or 14, characterized in that the cooking space is limited by a crucible ( 2 ) and one relative to the crucible ( 2 ) movable lid ( 3 ), whereby between the crucible ( 2 ) and the lid ( 3 ) preferably at least one sealing element ( 4 ) is arranged. Cooking appliance according to claim 15, characterized in that over the lid ( 3 ) the pressure sensor ( 6 ), a pressure relief valve ( 7 ) and / or a pressure relief valve ( 8th ) Can be brought into operative connection with the cooking chamber or are.