Method and apparatus for compensating temperature of microwave oven

Abstract: A method and an apparatus for compensating a temperature of a microwave oven, are disclosed. A first highest temperature of a load is detected during a current cycle. A second highest temperature of the load is detected during a last cycle. An actual temperature of the load is real time presumed based on a slope between the first and second highest temperatures. The presumed actual temperature and an actual temperature of the load detected by a sensor are real time compared to each other, and a higher one is set as a current temperature. A heating operation is controlled until the current temperature reaches a preset temperature.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method and an apparatus for compensating a temperature of a microwave oven, and more particularly, the present invention relates to a method and an apparatus for compensating a temperature of a microwave oven, which can compensate a temperature difference generated relying upon a rotating cycle of a turntable from a time when a temperature of food is detected. Description of the Prior Art Generally, a microwave oven is widely used in one's daily life, and accordingly, a higher usefulness is demanded because it is crucial to ensure reliability in end products. Recently, as various types of pre-cooked food are provided to consumers for affording instant cooking, a microwave oven serves as a cooking utensil which can quickly and easily perform cooking operations in an office or at a convenience store as well as home. When a microwave oven performs cooking operations, specific sensor means is used for controlling a heating operation. For example, when a microwave oven has an infrared sensor, a temperature of a load is detected by the infrared sensor, and a heating time is controlled based on the detected temperature. Also, when a microwave oven has a humidity sensor, a humidity is detected by the humidity sensor, and a heating time is controlled based on the detected humidity. Referring to FIGs. 1 and 2, there are shown front views which illustrate a hardware construction of the conventional microwave oven, and FIG. 3 is a block diagram illustrating a detailed construction of discriminating means of the conventional microwave oven. In a microwave oven of the prior art, a sensor hole 4 is formed on an upper portion of one of side walls which define a cooking compartment 1. An infrared sensor 5 is mounted in the microwave oven to detect a temperature of a load 7 located in the cooking compartment 1 through the sensor hole 4 while not being in contact with the load 7. A signal detected by the infrared sensor 5 is inputted to discriminating means 6. The discriminating means 6 controls a heating operation of heating means 3 which generates microwaves and operations of all another components, based on the signal detected by the infrared sensor 5. A turntable driving motor 8 is mounted below the cooking compartment 1, and is driven under a control of the discriminating means 6. A turntable 2 is fixed to a shaft of the turntable driving motor 8 centrally disposed in the cooking compartment 1. The load 7 which contains food to be cooked is put on the turntable 2. According to the microwave oven constructed as mentioned above, the discriminating means 6 controls the heating means 3 and the turntable driving motor 8 based on the signal detected by the infrared sensor 5. By this, the load 7 positioned in the cooking compartment 1 is heated by the microwaves generated by the heating means 3. The turntable 2 is rotated while the heating means 3 is actuated, to make the microwaves be dispersedly transferred to the load 7. Referring to FIG. 3, the discriminating means 6 includes a key input section 6a for inputting a key signal relying upon a cooking temperature, a cooking time and a kind of cooking, a preset temperature storing section 6b for storing the cooking temperature inputted through the key input section 6a or a preset temperature, a current temperature storing section 6c for temporarily storing a current temperature detected by the infrared sensor 5, a display section 6d for displaying through a liquid crystal display a simple message including the preset temperature, the current temperature, the cooking time, etc., and an output control section 6e for controlling an output by comparing the current temperature with the preset temperature. The discriminating means 6 discriminates the current temperature of the load 7 based on the signal detected by the infrared sensor 5. The discriminating means 6 performs the cooking operations by actuating the heating means 3 until the detected current temperature reaches the preset temperature. While the FIG. 1 shows the load 7 centrally positioned on the turntable 2, FIG. 2 shows the load 7 deviated from a center of the turntable 2. Hereinafter, the cooking operations of the microwave oven of the prior art, constructed as mentioned above, will be described in detail. Referring to FIG. 4, there is shown a flow chart for explaining cooking operations of the conventional microwave oven. A user puts the load 7 onto the turntable 2 in the cooking compartment 1, presets the cooking temperature through the key input section 6a to store the cooking temperature as the preset temperature into the preset temperature storing section 6b, and selects a cooking start key. At this time, the output control section 6e actuates the heating means 3 to heat the load 7. The output control section 6e is maintained in a stand-by state for about 5 seconds after heating of the load 7 begins, without sensing the temperature of the load 7 through the infrared sensor 5, to prevent an error from being induced on the detected temperature due to oscillating noise, etc. (step 110). The temperature of the load 7 put in the cooking compartment 1 is raised as the heating operation of the heating means 3 proceeds. The output control section 6e begins to receive the temperature signal detected by the infrared sensor 5 after a predetermined time (for example, of about 5 seconds) is lapsed since the heating operation is undertaken (step 120). The output control section 6e compares the current temperature of the load 7, which is detected by the infrared sensor 5, with the preset temperature (step 130). If the current temperature is lower than the preset temperature, the output control section 6e continues to actuate the heating means 3 thereby to heat the load 7. Also, if the current temperature reaches the preset temperature, the output control section 6e stops the operation of the heating means 3 to complete the cooking operations (step 140). In other words, in the cooking operations of the microwave oven of the prior art, the current temperature of the load 7, which is detected by the infrared sensor 5, is compared with the preset temperature. Then, if the current temperature is lower than the preset temperature, the heating means 3 is continuously actuated to heat the load 7. Also, if the current temperature reaches the preset temperature, the operation of the heating means 3 is stopped to complete the cooking operations. However, in the microwave oven of the prior art, since the cooking operations are performed by continuously heating the load 7 until the current temperature detected by the infrared sensor 5 reaches the preset temperature, even when the same food is cooked on the same cooking conditions, actual temperatures may be different from one another when the cooking operations are completed. This is because the current temperature detected by the infrared sensor 5 is varied in synchronization with a rotating cycle of the turntable 2. That is, as shown in FIG. 1, in case that the load 7 is centrally positioned on the turntable 2, when the current temperature of the load 7 reaches the preset temperature, the cooking operations are completed. The current temperature of the load 7 is detected in synchronization with the rotating cycle of the turntable 2 on a standard that the load 7 is centrally positioned on the turntable 2. However, as shown in FIG. 2, in case that the load 7 is deviated from the center of the turntable 2, the load 7 put on the turntable 2 may receive more heat and less heat when compared to the standard state as shown in FIG. 1. As a result, the load 7 can be more highly heated for a cycle time (generally, of about 10 through 24 seconds) (denoted as "dT" in FIG. 5) of the turntable 2 from a time when an actual temperature of the load 7 reaches the preset temperature. This is because the current temperature detected by the infrared sensor 5 is varied in synchronization with the rotating cycle of the turntable 2. Generally, a highest temperature among temperatures detected by the infrared sensor 5 is close to the actual temperature of the load 7. However, even when the actual temperature of the load 7 reaches the preset temperature at an initial stage of the rotating cycle of the turntable 2, the heating operation may be continued until a corresponding rotating cycle of the turntable is completely ended. This is because the discriminating means 6 discriminates whether the current temperature reaches the preset temperature only when a highest temperature is detected during the corresponding rotating cycle of the turntable 2. Accordingly, the discriminating means 6 continuously detects the temperature of the load 7 until the corresponding rotating cycle of the turntable 2 is completely ended. For this reason, the heating operation under the control of the discriminating means 6 is continuously performed until the corresponding rotating cycle of the turntable 2 is completely ended. Therefore, a time when the discriminating means 6 discriminates that the current temperature reaches the preset temperature, may be varied within the cycle time (of about 10 through 24 seconds) from the time when the actual temperature reaches the preset temperature. In particular, in case that an amount of food contained in the load 7 is small, the temperature of the food can be raised to a great extent for the rotating cycle of the turntable 2. For this reason, the temperature of the food after the cooking operations are completed, may be varied to a great extent when compared to the preset temperature. US 4 383 157 discloses an infrared radiation detector which is provided for receiving an infrared radiation emitted from a material being cooked placed in a cooking chamber in a microwave oven. The microwave oven is provided with a keyboard, a digital display and a microcomputer, such that when a temperature operation mode is set by entry from the keyboard the set temperature data is stored in a memory. In the temperature operation mode, the temperature of the material being cooked is detected in terms of a voltage associated with the output from the infrared radiation detector and a magnetron of the microwave oven is energized until the above described detected voltage becomes equal to the set temperature data and the magnetron is deenergized when both coincide with each other. In the temperature operation mode the temperature of the material being cooked is displayed by the digital display. SUMMARY OF THE INVENTION Accordingly, the present invention has been made in an effort to solve the problems occurring in the prior art, and an object of the present invention is to provide a method and an apparatus for compensating a temperature of a microwave oven, which can compensate a temperature difference generated relying upon a rotating cycle of a turntable from a time when a temperature of food reaches a preset temperature. According to the present invention the above object is achieved by a method according to claim 1 and by an apparatus a specified in claim 3. The dependent claim is directed to a further advantageous aspect of the invention. In order to achieve the above object, according to one aspect of the present invention, there is provided a method for compensating a temperature of a microwave oven, comprising the steps of: detecting a first highest temperature of a load during a current cycle; detecting a second highest temperature of the load during a last cycle; real time presuming an actual temperature of the load based on a slope between the first and second highest temperatures; real time comparing the presumed actual temperature and an actual temperature of the load detected by a sensor and setting a higher one as a current temperature; and controlling a heating operation until the current temperature reaches a preset temperature. In order to achieve the above object, according to another aspect of the present invention, there is provided an apparatus for compensating a temperature of a microwave oven, comprising: detecting means for detecting a temperature of a load; first storing means for storing a first highest temperature of the load detected by the detecting means during a current rotating cycle and a second highest temperature of the load detected by the detecting means during a last rotating cycle; second storing means for storing a preset temperature in accordance with a kind of cooking; third storing means for storing an actual temperature of the load real time presumed based on a slope between the first and second highest temperatures; and controlling means for real time comparing the presumed actual temperature and an actual temperature of the load detected by a sensor, setting a higher one as a current temperature, and controlling a heating operation until the current temperature reaches the preset temperature. In the present invention, the highest temperature of the load detected during the last rotating cycle of the turntable, which just precedes the current cycle, is referred to as a latter cycle temperature, and a time when the latter cycle temperature is detected is referred to as a latter cycle temperature detecting time. Also, another highest temperature of the load detected during a one before the last cycle of the turntable; which just precedes the last cycle in which the latter cycle temperature is detected, is referred to as a former cycle temperature. The slope is calculated based on the former cycle temperature and the latter cycle temperature obtained in these ways, and the actual temperature is presumed using the slope. In addition, according to the present invention, the presumed actual temperature and the actual temperature of the load detected by the sensor are compared to each other, and the higher one is set as the current temperature. Then, it is discriminated whether the set current temperature reaches the preset temperature. Hence, since the microwave oven of the present invention presumes an actual temperature of food based on a time when a highest temperature is detected while grasping temperature variations during past rotating cycles of a turntable, it is possible to precisely control the temperature of the food. BRIEF DESCRIPTION OF THE DRAWINGS The above objects, and other features and advantages of the present invention will become more apparent after a reading of the following detailed description when taken in conjunction with the drawings, in which: FIGs. 1 and 2 are front views illustrating a hardware construction of the conventional microwave oven; FIG. 3 is a block diagram illustrating a detailed construction of discriminating means of the conventional microwave oven of FIGs. 1 and 2; FIG. 4 is a flow chart for explaining cooking operations of the conventional microwave oven; FIG. 5 is a graph illustrating a relationship between a detected temperature and an actual temperature of a load in the conventional microwave oven; FIG. 6 is a block diagram illustrating a detailed construction of discriminating means which performs a temperature compensating control in accordance with an embodiment of the present invention; FIG. 7 is a flow chart for explaining a method for compensating a temperature of a microwave oven, according to the present invention; and FIG. 8 is a graph illustrating a relationship between a detected temperature and an actual temperature of a load in the microwave oven of the present invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts. Hereinafter, a hardware construction of a microwave oven of the present invention will be described with reference to FIG. 1, and a detailed construction of discriminating means according to the present invention will be described with reference to FIG. 6. Also, hereinafter, a highest temperature of a load detected during a last rotating cycle n-1 of a turntable 2, which just precedes a current cycle n, is referred to as a latter cycle temperature, and a time when the latter cycle temperature is detected is referred to as a latter cycle temperature detecting time. Also, another highest temperature of the load detected during a one before the last cycle n-2 of the turntable 2, which just precedes the last cycle n-1 in which the latter cycle temperature is detected, is referred to as a former cycle temperature. In the microwave oven of the present invention, a sensor hole 4 is formed on an upper portion of one of side walls which define a cooking compartment 1. An infrared sensor 5 is mounted in the microwave oven to detect a temperature of a load 7 located in the cooking compartment 1 through the sensor hole 4 while not being in contact with the load 7. A signal detected by the infrared sensor 5 is inputted to discriminating means 6. The discriminating means 6 controls a heating operation of heating means 3 which generates microwaves and operations of all another components, based on the signal detected by the infrared sensor 5. A turntable driving motor 8 is mounted below the cooking compartment 1, and is driven under a control of the discriminating means 6. A turntable 2 is fixed to a shaft of the turntable driving motor 8 centrally disposed in the cooking compartment 1. The load 7 which contains food to be cooked is put on the turntable 2. The discriminating means 6 includes a key input section 6A for inputting a cooking temperature, a cooking time and a cooking start key, etc., a first temperature storing section 6B for storing the cooking temperature inputted through the key input section 6A and/or a preset temperature, a second temperature storing section 6C for storing a current temperature detected by the infrared sensor 5, and a display section 6D for displaying the preset temperature, the current temperature, the cooking time, etc. Also, the discriminating means 6 includes an output control section 6F for controlling an output by comparing the preset temperature and the current temperature, a timer 6K for counting the cooking time, a third temperature storing section 6E for storing a temperature of the load 5 during the one before the last rotating cycle n-2, and a fourth temperature storing section 6G for storing a temperature of the load 5 during the last rotating cycle n-1. Further, the discriminating means 6 includes a cycle counter 6H for counting a rotating cycle time of the turntable 2, a time storing section 6J for storing a time when the highest temperature of the last rotating cycle n-1 is detected, a preset temperature reaching flag 6I for setting the fact that the preset temperature is reached in the current cooking operations, and a fifth temperature storing section 6L for storing a temperature presumed, based on a slope between the former rotating cycle temperature and the latter rotating cycle temperature. The discriminating means 6 constructed as mentioned above, controls the cooking operations of the microwave oven in accordance with the preset temperature. When a user presets through the key input section 6A the cooking temperature (preset temperature) to be reached, the preset temperature is stored in the first temperature storing section 6B under a control of the output control section 6F. At this time, the output control section 6F remembers the preset temperature until the current cooking operations are completed. Also, when the user presets the cooking time through the key input section 6A, the output control section 6F remembers the preset cooking time. Thereafter, when the user inputs the cooking start key, the output control section 6F controls the heating means 3 in accordance with the preset cooking time and the preset temperature to effect a desired cooking. The temperature of the load 7 is raised as the heating operation of the heating means 3 proceeds. The infrared sensor 5 detects the temperature of the load 7 through the sensor hole 4. The output control section 6F stores the detected current temperature of the load 7 into the second temperature storing section 6C which is a current temperature storing section. Further, the highest temperature of the load 7 detected during the last rotating cycle n-1 of the turntable 2, which just precedes the current cycle n, is stored as the latter cycle temperature into the fourth temperature storing section 6G. Also, the time when the latter cycle temperature is detected, which is referred to as the latter cycle temperature detecting time, is stored into the time storing section 6J. In addition, the highest temperature of the load 7 detected during the one before the last cycle n-2 of the turntable 2, which just precedes the last cycle n-1 in which the latter cycle temperature is detected, is stored into the third temperature storing section 6E as the former cycle temperature. The output control section 6F calculates the slope based on the former rotating cycle temperature and the latter rotating cycle temperature, and determines the presumed temperature based on the slope calculated. This presumed temperature is stored into the fifth temperature storing section 6L. The output control section 6F compares the presumed temperature stored into the fifth temperature storing section 6L and the current temperature stored into the second temperature storing section 6C, and determines a higher one as an actual current temperature of the load 7. Then, the output control section 6F controls the cooking operations for the preset cooking time while comparing the determined actual current temperature and the preset temperature stored into the first temperature storing section 6B and discriminating whether the actual current temperature reaches the preset temperature. Hereinbelow, a method for compensating a temperature of the microwave oven constructed as mentioned above will be described in detail. Referring to FIG. 7, there is shown a flow chart for explaining a method for compensating a temperature of a microwave oven, according to the present invention, and FIG. 8 is a graph illustrating a relationship between a detected temperature and an actual temperature of a load in the microwave oven of the present invention. When the user puts the load 7 onto the turntable 2 in the cooking compartment 1 and presets the cooking temperature through the key input section 6A, the preset temperature is stored into the first temperature storing section 6B. Thereafter, when the user selects the cooking start key, the output control section 6F actuates the heating means 3 to heat the load 7. The output control section 6F is maintained in a stand-by state for about 5 seconds after heating of the load 7 begins, without sensing the temperature of the load 7 through the infrared sensor 5, to prevent an error from being induced on the detected temperature due to oscillating noise, etc. (step 201). The temperature of the load 7 is raised by the continuous heating, and the output control section 6F receives the temperature detected by the infrared sensor 5 (step 203). The output control section 6F compares the current temperature detected by the infrared sensor 5 with the latter cycle temperature which is the highest temperature detected during the last rotating cycle n-1 of the turntable 2 (step 205). The reason why the output control section 6F compares the current temperature with the latter cycle temperature, is in that the latter cycle temperature means the highest temperature among temperatures detected up to current time. The output control section 6F stores a higher one of the two temperatures, compared to each other, as the latter cycle temperature into the fourth temperature storing section 6G (step 207). Of course, as described above, it is explained that the highest temperature detected during not the current rotating cycle n but the last rotating cycle n-1 is considered as the latter cycle temperature. However, this is just one way in which information needed to calculate the slope, is expressed (namely, former cycle temperature or latter cycle temperature), as will be described in step 227. As a result, this is similar to the fact that when the next cycle n proceeds, the highest temperature detected during the current cycle n-1 is set as the latter cycle temperature. Further, the time when the highest temperature is obtained, is detected in step 207 and is stored into the time storing section 6J (step 209). The procedures of step 205 through step 209 for storing the highest temperature as the latter cycle temperature, are repeated until the cycle counter 6H for counting the cycle time of the turntable 2 outputs a signal which informs of the completion of one rotating cycle (step 211). The cycle counter 6H increases its counting value by 1 every time when the current temperature detected by the infrared sensor 5 and the highest temperature of the last cycle are compared to each other and a higher one is set as the latter cycle temperature (step 213). At this time, while the cycle time T of the cycle counter 6H can be set to the rotating cycle time of the turntable 2, the cycle time T of the cycle counter 6H can be set to a value in which a predetermined amount is added to the rotating cycle time of the turntable 2. When the cycle counter 6H outputs the signal which informs of the completion of one rotating cycle of the turntable 2, the cycle counter 6H is initialized to a value of "0" (step 215). At this time, the latter cycle temperature stored into the fourth temperature storing section 6G is substituted for the former cycle temperature and stored into the third temperature storing section 6E (step 217). The output control section 6F discriminates whether a counting value of the cycle counter 6K for counting the cooking time corresponds to a time which is obtained by multiplying the cycle time T of the turntable 2 by a number of cycles n and then adding 5 seconds (step 219). The 5 seconds are the time during which the output control section 6F is maintained in a stand-by state to prevent an error from being induced on the detected temperature due to oscillating noise, etc. Accordingly, if an answer in step 219 is negative, it is discriminated by the output control section 6F that the complete rotation of the turntable 2 has not occurred. However, if the answer in step 219 is positive, the output control section 6F substitutes the latter cycle temperature stored into the fourth temperature storing section 6G for the former cycle temperature to store into the third temperature storing section 6E (step 221). At the same time, the output control section 6F sets an initial value of the fourth temperature storing section 6G as the latter cycle temperature (step 223). Then, the time when the highest temperature is detected during the last cycle, is stored into the time storing section 6J (step 225). The reason why data stored into the fourth temperature storing section 6G is set as the latter cycle temperature in step 223, is for setting the highest temperature detected during a previous rotating cycle of the turntable 2 as a reference value to be compared with a temperature detected during a subsequent rotating cycle of the turntable 2, before the rotation of the turntable 2 in the subsequent rotating cycle is initiated. Accordingly, in this case, the data stored into the third and fourth temperature storing sections 6E and 6G are set as the same latter cycle temperatures. When a rotating cycle of the turntable 2 is completed through the above described procedures, since steps 221 through 225 are just completed, it is to be readily understood that the former cycle temperature and the latter cycle temperature become identical to each other. Also, within the rotating cycle of the turntable 2, in the course of performing steps 205 thorough 213, it can be presumed that the former cycle temperature and the latter cycle temperature may be set such that they are different from each other. Through the above described procedures, the highest temperature detected during the last rotating cycle of the turntable 2 is stored into the fourth temperature storing section 6G, and the highest temperature detected during the one before the last cycle is stored into the third temperature storing section 6E. Further, the time when the latter cycle temperature is detected is stored into the time storing section 6J. Then, the output control section 6F calculates the presumed temperature by the following equation based on the slope between the former cycle temperature and the latter cycle temperature by using the latter cycle temperature, former cycle temperature, the latter cycle temperature detecting time and the current time (step 227). Presumed temperature = (latter cycle temperature - former cycle temperature)/T X (current time - latter cycle temperature detecting time) + latter cycle temperature. The presumed temperature is calculated in step 227 based on the slope between the latter cycle temperature and the former cycle temperature, and the output control section 6F stores the temperature presumed as described above into the fifth temperature storing section 6L. Further, the output control section 6F compares the presumed temperature stored into the fifth temperature storing section 6L with the current temperature of the load 7 detected by the infrared sensor 5 and stored into the second temperature storing section 6C (step 229), and sets a higher one as the actual current temperature of the load 7. Namely, if the presumed temperature is higher than the current temperature in step 229, the presumed temperature becomes the actual current temperature (step 231), and if the current temperature is higher than the presumed temperature, the current temperature becomes the actual current temperature. The output control section 6F compares the actual current temperature set in step 231 with the preset temperature stored into the first temperature storing section 6B (step 233), and if the actual current temperature reaches the preset temperature, sets the preset temperature reaching flag 6I to complete the cooking operations (step 235). However, if the actual current temperature is lower than the preset temperature in step 233, the output control section 6F returns to step 203 to read out the current temperature detected by the infrared sensor 5. In this case, the heating operation of the heating means 3 is continued under the control of the output control section 6F. When the output control section 6F returns to step 203, the output control section 6F compares in step 205 the current temperature read out from the infrared sensor 5 with the highest temperature detected during the last rotating cycle and stored into the fourth temperature storing section 6G, and presets a higher one as the latter cycle temperature and stores the latter cycle temperature again into the fourth temperature storing section 6G (step 207). The above procedures are performed until one rotating cycle of the turntable 2 is completed (step 211). Even before the one rotating cycle of the turntable 2 is completed, the presumed temperature is continuously calculated in step 227 using the latter cycle temperature stored into the fourth temperature storing section 6G, the former cycle temperature stored into the third temperature storing section 6E, and the latter cycle temperature detecting time, etc. In step 229, the presumed temperature is compared with the current temperature detected from the infrared sensor 5, a higher one is set as the actual current temperature, and the actual current temperature is compared with the preset temperature (step 233). If the actual current temperature does not reach the preset time while step 233 is repeated, the output control section 6F continues to detect the current temperature from the infrared sensor 5, while monitoring a counting value of the cycle counter 6H (step 211). When the cycle counter 6H outputs the signal which informs of the completion of one rotating cycle time T of the turntable 2 in step 211, if the actual current temperature does not reach the preset temperature, the latter cycle temperature stored into the fourth temperature storing section 6G is stored into the third temperature storing section 6E (step 217). Then, a temperature detected based on the latter cycle temperature stored into the fourth temperature storing section 6G is compared with the presumed temperature, and a procedure in which a higher one is compared with the preset temperature is performed. Referring to FIG. 8, there is shown a graph illustrating a relationship between a detected temperature and an actual temperature of a load in the microwave oven of the present invention. According to the present invention, the load 7 is put into the cooking compartment 1 of the microwave oven having the infrared sensor 5, the temperature is set through the key input section 6A, the preset temperature is stored into the first temperature storing section 6B, and then the cooking operations are began. Thereafter, the output control section 6F reads out the current temperature of the load 7 detected through the infrared sensor 5 during the rotating cycle of the turntable 2. The highest temperature of the load 7 detected during the last cycle is referred to as the latter cycle temperature, and the time when the latter cycle temperature is detected is referred to as latter cycle temperature detecting time. Also, the highest temperature of the load 7 detected during the one before the last cycle is referred to as the former cycle temperature. The presumed temperature is calculated by the following equation using the slope between the former cycle temperature and the latter cycle temperature. Presumed temperature = (latter cycle temperature - former cycle temperature)/T X (current time - latter cycle temperature detecting time) + latter cycle temperature. The presumed temperature calculated as described above is compared with the current temperature detected by the infrared sensor 5, and a higher one is set as the actual current temperature. Then, the actual current temperature of the load and the preset temperature are compared to each other to determine whether the actual current temperature reaches the preset temperature. As described above, according to the present invention, advantages are provided in that since a temperature of a load is real time presumed and discriminated in cooking operations of a microwave oven having an infrared sensor, it is possible to precisely control a temperature of the microwave oven. In particular, even in case that an amount of food contained in a load is small, a temperature of the food is prevented from being raised to a great extent after the cooking operations are completed. In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.

Claims: A method for controlling a temperature of a load (7) in an oven, said oven being a microwave oven including a rotating turntable therein, comprising: detecting a highest temperature of the load (7) during a current time cycle; detecting a highest temperature of the load (7) during a prior time cycle immediately preceding the current time cycle; wherein the current and prior time cycles are rotation cycles of the turntable (2); real time estimating an actual temperature of the load (7) based on the slope between the highest temperature during the current time cycle and the highest temperature during the prior time cycle; real time comparing the estimated actual temperatureof the load (7) and a detected actual temperature of the load (7) detected by a detecting means (5) and defining the higher of the two as a current temperature of the load (7); and controlling a heating operation of the oven until the current temperature of the load (7) reaches a preset temperature. The method according to claim 1, wherein the estimated actual temperature of the load (7) is determined by an expression: ((the highest temperature of the current time cycle - the highest temperature of the prior time cycle)/time length of the time cycle)*(current time - time at which the highest temperature of the current time cycle is detected)+(the highest temperature of the current time cycle). An apparatus for controlling a temperature of a load (7) in an oven, comprising: a detecting means (5) for detecting a temperature of the load (7); a first storing means (6B) for storing the highest temperature of the load (7) detected by said detecting means (5) during a current time cycle and the highest temperature of the load (7) detected by said detecting means (5) during a prior time cycle immediately prior to said current time cycle; a second storing means (6C) for storing a preset temperature in accordance with a kind of cooking; a third storing means (6E) for storing an estimated actual temperature of the load (7), said estimated actual temperature being obtained from a slope between the highest temperature of said current time cycle and the highest temperature of said prior time cycle; and a controlling means (6) for real time comparing said estimated actual temperature of the load (7) and said detected actual temperature of the load (7) detected by said detecting means (5), setting the higher of the two temperatures as a current temperature of the load (7), and controlling a heating operation of the oven until said current temperature of the load (7) at least reaches said preset temperature.

Inventors: PARK WON KYUNG, PARK, WON KYUNG
Applicants: LG ELECTRONICS INC, LG ELECTRONICS INC.
Application year: 1998
Main classification: H05B6
IPC codes: H05B6