CN101763127B - Control method of pressure cooker - Google Patents

Abstract

The invention relates to a control method of a pressure cooker, which comprises the following steps: A. setting various control parameters through a function keyboard of the pressure cooker; B. testing and recording the initial temperature of the pressure cooker, and starting heating with full power, after a preset time, recording the temperature as the secondary initial temperature; C. according to the control parameters and the temperature difference in the preset time obtained in the step B, predicting the target heating time that the heated object achieves the target heating temperature or target heating pressure; and D. starting from the second initial temperature, measuring the actual temperature of the pressure cooker at regular intervals, and obtaining the corresponding actual pressure and actual time by calculation. The invention has the beneficial effects that: (1) since pressure parameters can be directly calculated through the temperature detected by a temperature sensor, the pressure cooker can be intelligently controlled through temperature parameters, and a pressure sensing device and a corresponding A / D converter can be omitted, thereby effectively reducing cost.

Description

A kind of control method of pressure cooker

technical field

The invention belongs to household electric cooking equipment, in particular to a control method for a pressure cooker.

Background technique

Household appliances, especially household electric cooking equipment, such as electric rice cookers and electric pressure cookers have become indispensable electrical appliances in people's daily life. The automation of household appliances is an important development direction. Temperature is an important parameter in electric cooking equipment. People often use temperature sensing as an important sensing signal for automatic control, and it is one of the basis for controlling the cooking process. In an electric pressure cooker, besides the temperature, the pressure in the pot becomes the second important control parameter. The pressure in the pressure cooker is not only a parameter as important as the temperature in the normal cooking process, affecting the quality of cooking, but also closely related to the safety of cooking. Uncontrolled pressure is often the main cause of accidents. As shown in Figure 1, in existing pressure cooker mainly by outer pot body 1, inner pot body 2, pot lid 3, sealing ring 4, pressure insurance valve 5, temperature sensor 6, heating controller 7, electric heating body 8, Pressure spring 9 and weighing sensor 10 are formed, and the sensing of pressure is mainly completed by the pressure sensing device that pressure spring 9 and weighing sensor 10 are formed, and its principle is, the inner pot body 2 of pressure cooker passes pressure spring 9 and pressure cooker The outer pot body 1 is connected, and when heating increases the pressure in the inner pot body 2, the pressure overcomes the elastic force of the rubber ring 9, so that the inner pot body 2 moves downward. This displacement can be sensed by the load cell 10 at the bottom of the outer pot body 1, and becomes an electric signal, and the automatic control action is completed by the control circuit. The existing pressure cooker has the following disadvantages (1) The pressure cooker is controlled by pressure parameters. In order to obtain the pressure parameters of each control stage, an additional pressure sensing device needs to be installed, and the structure of the outer pot body is more complicated, which increases the cost. (2) The corresponding A/D converter is added. (3) Control is performed by setting the pressure as a threshold value. In case of errors in the acquisition of pressure parameters, it will cause a greater safety hazard.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the deficiency that the control process of the existing pressure cooker must be controlled by means of an additional pressure sensing device, and proposes a control method for the pressure cooker. At the same time, the reliability of the control process can also be improved.

The technical solution of the present invention is realized according to the following steps: a control method of a pressure cooker, comprising the steps of:

A. Set various control parameters through the function keyboard of the pressure cooker;

B. Test and record the initial temperature of the pressure cooker, start heating with full power, after a predetermined time, record the temperature at this time as the secondary initial temperature;

C. Predict the target heating time for the object to be heated to reach the target heating temperature or target heating pressure according to the temperature difference obtained in the predetermined time period obtained in the control parameter and step B;

D. Starting from the secondary initial temperature, measure the actual temperature of the pressure cooker at regular intervals, and calculate the corresponding actual pressure and actual time at this time;

E. Compare the actual temperature, actual pressure or actual time obtained in step D with the target heating temperature, target heating pressure or target heating time, if the actual temperature, actual pressure or actual time is less than its corresponding target heating temperature, target heating pressure or target heating time, then step D is performed in a loop; if any item (or any several items) of actual temperature, actual pressure or actual time is greater than or equal to its corresponding target heating temperature, target heating pressure or target heating time, then Stop heating and let the pressure cooker cool down naturally;

F. From the stop of heating, measure the actual temperature of the pressure cooker at regular intervals. If the actual temperature is lower than the first heat preservation temperature, enter the first heat preservation stage, and the time of the first heat preservation stage is the preset value.

G. After the preset time of the first heat preservation stage, stop heating, measure the actual temperature of the pressure cooker at a fixed time interval, if the actual temperature is lower than the second heat preservation temperature, enter the second heat preservation stage, the second The time of the second heat preservation stage is a preset value.

The beneficial effects of the present invention are: (1) Since the present invention utilizes the functional relationship between the temperature of the pressure cooker and the internal pressure, the pressure parameter can be directly deduced from the temperature detected by the temperature sensor, thus the pressure cooker can be directly intelligently controlled through the temperature parameter , omitting the pressure sensing device and the corresponding A/D converter, which effectively reduces the cost. (2) Secondly, in the intelligent control process of the pressure cooker, the real-time weighing program (that is, the quality of the object to be heated can be calculated from the temperature rise of the pot body within a given time) can be given to reach the target heating temperature. The optimal target heating time further improves the precise time control of the pressure cooker. (3) For the control of the heating process, multiple thresholds such as target heating temperature, target heating pressure, and target heating temperature can be set at the same time, which further improves the reliability of the pressure cooker.

Description of drawings

Fig. 1 is the structural principle diagram of traditional electric heating pressure cooker.

Fig. 2 is a structural principle diagram of the electric heating pressure cooker of the present invention.

Fig. 3 is a coordinate schematic diagram of heating time, heating pressure and heating temperature of the electric heating pressure cooker.

Fig. 4 is a control main flowchart of the present invention.

Fig. 5 is the control flowchart of the first heat preservation stage of the present invention.

Fig. 6 is the control flowchart of the second heat preservation stage of the present invention.

Explanation of reference signs: outer pot body 1, inner pot body 2, pot cover 3, sealing ring 4, pressure safety valve 5, temperature sensor 6, heating controller 7, electric heating body 8, pressure spring 9, load cell 10 , the initial temperature T ₀ , the second initial temperature T _u , the temperature difference T _d within the predetermined time, the second holding temperature T _b2 , the second holding pressure P _b2 , the first holding temperature T _b1 , the first holding temperature pressure P _b1 , target heating temperature T _m , target heating pressure P _m , and target heating time t _m .

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

The technical improvement of the present invention is mainly based on the following theory: (a) in the process of electric heating, the heating time for a certain mass to be heated to a certain temperature is proportional to the heating temperature difference per unit time under ideal conditions. Considering various actual influencing factors, there is a relational formula like (2).

(b) Prediction of heating time. Suppose the initial temperature of the heating body is T ₀ ; the temperature measured after heating for a predetermined time u (u=60 seconds in this embodiment) is taken as the secondary initial temperature T _u , then the temperature difference of heating for u seconds is

T _d =T _u -T ₀ formula (1)

Then the target temperature time required to be heated to the temperature T _m is

$t_m=A\frac{T_m-T_u}{T_u-T_0}=A\frac{T_m-T_u}{T_d}$ Formula (2)

Among them, A is the time factor caused by radiation and air convection in the heating process, which is related to the specific environment and is a constant quantity.

(c) Target temperature time t _m prediction.

Example 1: Heat 3.865kg of water (ambient temperature 27.5°C); initial temperature T ₀ =23.9°C; temperature T _u =28.2°C after heating for one minute (u=60 seconds); therefore, there is a temperature difference T _d =4.3 °C; heating from _Tu = 28.2 °C to T _m = 97 °C (the boiling point of water in Chengdu area), according to (2) the required target temperature time t _m = 16 minutes (take A = 1.0). The measured time t _s =16.5 minutes, so the corrected A=16.5/16=1.03.

Example 2: Heat 4.15kg of water (ambient temperature 23.5°C); initial temperature T ₀ =22.3°C; temperature T _u =26.8°C after heating for one minute (u=60 seconds); therefore, there is a temperature difference T _d =4.5 °C; heating from _Tu = 26.8 °C to T _m = 97 °C (the boiling point of water in Chengdu area), according to (2) the required target temperature time t _m = 15.6 minutes (take A = 1.0). The measured time t _s =17.2 minutes, so the corrected A=17.2/15.6=1.10.

Through the above two examples, it is further proved that in the process of electric heating, the heating time for a certain mass to be heated to a certain temperature is proportional to the heating temperature difference per unit time under ideal conditions.

According to the ideal gas formula and the actual test results, the pressure in the pressure cooker after heating also has a relationship similar to the temperature, that is, the heating time for a certain mass to be heated to a certain pressure in the process of electric heating, and the heating pressure per unit time. Ideally proportional.

Assuming that the pressure P _m in the pressure cooker is related to the ratio S of the volume occupied by the object to be heated to the volume of the air part and the temperature T _m of the pressure cooker after heating, that is, the pressure P _m is a function of S and T _m , which is recorded as P _m = (S, T _m ). P _m = (S, T _m ) can be obtained by theoretical derivation or actual measurement.

The theoretical derivation process of P _m is further described below to prove the correctness of the above theory and reveal the intrinsic functional relationship between temperature and pressure in the pressure cooker.

From the related gas pressure theory, we have the following (3)

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}{\mathrm{<span\; class="notranslate">\; V</span>}}{\mathrm{<span\; class="notranslate">\; N</span>}}^{<span\; class="notranslate">\; \&prime;</span>}\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Among them, P _m is the pressure in the pressure cooker, the unit is Pa; T _m is the temperature of the pressure cooker measured by the temperature sensor, the unit is the absolute temperature K; V is the volume of the air part in the pressure cooker, the unit is m ³ ; N′ is the corrected The number of particles, there are (4)

${\mathrm{<span\; class="notranslate">\; N</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; V</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

α(S, T _f ) is related to the actual environment, where S is the ratio of the volume of the heated object to the volume of the air in the pressure cooker, P ₀ is an atmospheric pressure, T ₀ is taken as 20°C+273, and the unit is absolute temperature K, k is Boltzmann's constant, can be given by (5) by the relational expression of the temperature T _m of the pressure P _m in (4) and pressure cooker:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}{\mathrm{<span\; class="notranslate">\; V</span>}}{\mathrm{<span\; class="notranslate">\; N</span>}}^{<span\; class="notranslate">\; \&prime;</span>}\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}{\mathrm{<span\; class="notranslate">\; V</span>}}\mathrm{<span\; class="notranslate">\; k\&alpha;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; V</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>\frac{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Therefore, if we know the relationship between the pressure P _m and the temperature T _m under various S conditions, the pressure P m _of the pressure cooker corresponding to the temperature can be calculated from the temperature T _m of the pressure cooker. That is to say, we can still calculate the target pressure time t _P required to reach the predetermined pressure P _m from the measurement of the temperature rise of the pot body per unit time. Usually, as shown in Figure 3, the control process of the pressure cooker of the present invention mainly includes the following several stages: a. Heating stage, this stage needs preset target heating temperature T _m and target heating pressure P _m ; b. heat preservation for the first time stage, this stage needs to preset the first holding temperature T _b1 and the first holding pressure P _b1 ; c. the second holding stage, this stage needs to preset the second holding temperature T _b2 and the second holding pressure P _b2 .

Describe in detail the specific implementation process of the present invention below in conjunction with accompanying drawing 4 and specific embodiment: a kind of control method of pressure cooker, comprises the steps:

A. Set various control parameters through the function keyboard of the pressure cooker. These control parameters include the second heat preservation pressure P _b2 , the first heat preservation temperature T _b1 , the first heat preservation pressure P _b1 , the target heating temperature T _m , the target heating pressure P _m and the volume of the air part of the pot body before heating and the heated Food volume ratio S.

B. Test and record the initial temperature T ₀ of the pressure cooker, start heating with full power, after a predetermined time, record the temperature at this time as the secondary initial temperature T _u . In this embodiment, the temperature of the pot body before the heating is selected as the initial temperature T ₀ , and the temperature 60 seconds after the heating is selected as the secondary initial temperature T _u .

C. Predict the target heating pressure P _m or the target heating time t _m to reach the target heating temperature T _m according to the control parameters and the temperature difference within a predetermined time obtained in step B. From the formula (1), we can know the temperature difference T _d of an object with a certain mass after heating for 60 seconds from the initial temperature T ₀ , and then from the formula (2), we can know the target heating time t _m to reach the target heating temperature T _m , according to ( 5) Obtain the target heating pressure P _m .

D. Starting from the secondary initial temperature T _u , measure the actual temperature T _s of the pressure cooker at regular intervals, and calculate the corresponding actual pressure P _s and actual time t _s at this time. In this step, the fixed time interval is set to 10 seconds, of course, other appropriate time can also be set as required. The actual pressure P _s and the actual temperature T _s still satisfy (5), so the actual pressure P _s can be obtained from the measured actual temperature T _s according to (5).

E. Compare the actual temperature T _s , actual pressure P _s or actual time t _s obtained in step D with the target heating temperature T _m , target heating pressure P _m or target heating time t _m , if the actual temperature T _s , actual If the pressure P _s or the actual time t _s is less than the corresponding target heating temperature T _m , target heating pressure P _m or target heating time t _m , then step D is performed in a loop; if the actual temperature T _s , actual pressure P _s or actual time If any item of t _s is greater than or equal to its corresponding target heating temperature T _m , target heating pressure P _m or target heating time t _m , stop heating and let the pressure cooker cool down naturally;

F. From the stop of heating, measure the actual temperature T _s of the pressure cooker at regular intervals. If the actual temperature T _s is lower than the first heat preservation temperature T _b1 , enter the first heat preservation stage, and the time for the first heat preservation stage t _b1 is the default value. The fixed time interval in this step is 2 minutes, and of course other appropriate time can also be set as required. The time t _b1 of the first heat preservation stage can be set arbitrarily within a fixed time as required.

Concrete steps as shown in Figure 5, after starting to enter the heat preservation stage for the first time, measure the actual temperature T _s of the pressure cooker at every fixed time interval (2 minutes in this embodiment), if the actual temperature T _s is greater than or equal to the second Stop heating at the first holding temperature T _b1 ; if the actual temperature T _s is lower than the first holding temperature T _b1 , start to calculate the holding time t _s at the same time, and continue heating for 2 minutes at the same time to judge the holding time t _s and the first holding stage The relationship between the size of the time t _b1 , if t _s is greater than or equal to t _b1 , then the first heat preservation stage is ended, otherwise, this step is performed in a loop.

G. After the preset time t _b1 of the first heat preservation stage, stop heating, measure the actual temperature T _s of the pressure cooker at regular intervals, if the actual temperature T _s is less than the second heat preservation temperature T _b2 , enter In the second heat preservation stage, the time t _b2 of the second heat preservation stage is a preset value. The fixed time interval in this step is 2 minutes, and of course other appropriate time can also be set as required. The time t _b2 of the second heat preservation stage can be arbitrarily set as a fixed time or an infinite time according to needs, and the time t _b2 of the second heat preservation stage in this step is preset as an infinite time.

Concrete steps as shown in Figure 6, after starting to enter the second heat preservation stage, measure the actual temperature T _s of the pressure cooker every fixed time interval (2 minutes in this embodiment), if the actual temperature T _s is greater than or equal to the first If the second holding temperature T _b2 , stop heating; if the actual temperature T _s is lower than the second holding temperature T _b2 , continue heating for 2 minutes, and continue this step in a cycle.

As shown in FIG. 2 , it is a structural principle diagram of an electric heating pressure cooker whose structure can be simplified after applying the control method of the present invention. It mainly consists of an outer pot body 1, an inner pot body 2, a pot cover 3, a sealing ring 4, a pressure safety valve 5, a temperature sensor 6, a heating controller 7, and an electric heating body 8. It can be seen that the pressure cooker omits the weighing device, and its control process depends on the detected temperature parameter, and the pressure parameter can be obtained through the function between temperature and pressure.

Those skilled in the art will appreciate that the embodiments described herein are to help readers understand the principles of the present invention, and it should be understood that the protection scope of the invention is not limited to such specific statements and embodiments. All possible equivalent replacements or changes made according to the above descriptions are deemed to belong to the protection scope of the claims of the present invention.

Claims (1)

1. the control method of a pressure cooker is characterized in that, comprises the steps:

A. the function keyboard through pressure cooker is provided with various control parameters;

B. test and write down the initial temperature of pressure cooker, the beginning heating with full power, after a schedule time, record temperature this moment is as the secondary initial temperature;

C. according to the temperature difference in the schedule time that obtains among controlled variable and the step B, dope the target heat time heating time that heating object reaches target heating-up temperature or target heated pressure;

D. begin from the secondary initial temperature, every actual temperature at a distance from a set time gaging pressure pot, and calculate at this moment corresponding actual pressure and real time;

E. the actual temperature that obtains among the step D, actual pressure or real time and target heating-up temperature, target heated pressure or target are compared heat time heating time; If actual temperature, actual pressure or real time, all less than its corresponding target heating-up temperature, target heated pressure or target heat time heating time, then step D was carried out in circulation; If actual temperature, actual pressure or real time each more than or equal to its corresponding target heating-up temperature, target heated pressure or target heat time heating time, then stop heating pressure cooker lowered the temperature naturally;

F. from stopping the heating beginning, whenever at a distance from the actual temperature of a Fixed Time Interval gaging pressure pot, if actual temperature less than the holding temperature first time, then gets into holding stage for the first time, the time of holding stage is preset value for the first time;

G. after the preset time through the holding stage first time; Stop heating, every actual temperature at a distance from a Fixed Time Interval gaging pressure pot is if actual temperature is less than the holding temperature second time; Then get into holding stage for the second time, the time of holding stage is preset value for the second time.

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