Abstract:
A microwave oven comprising a power supply, a heating chamber having a door, a detector for detecting the opening and closing of the door, a high-frequency heater for heating the article to be heated, a plurality of setting keys for setting heating time, a timer for driving the heater for a specified period of time, a starter for initiating the timer into operation after a predetermined period of time beginning after the depression of the setting key, a stopper for temporarily preventing the operation of the timer when the cooking is interrupted by opening of the door, and a control unit for driving the timer again when the cooking operation is resumed on closing the door. The setting key functions also as a start key, and when the door is opened and closed during cooking, the article can be heated only for the rest of the heating time by depressing the original setting key. The heating time can also be adjustable to a new heating time.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a microwave oven having a microcomputer incorporated therein, and more particularly, to a microwave oven which uses simplified key manipulation. 
     2. Description of the Prior Art 
     Conventional microwave ovens are adapted to store cooking conditions upon setting heating time with a heating time setting key and entering an output power level and the like using other function keys and to thereafter start cooking upon depression of a start key. When the door is opened during the cooking cycle to interrupt the cooking, the remaining heating time is displayed and stored. When cooking is to be resumed, the start key is depressed again after closing the door, thereby continuing the cooking for the rest of the time. If it is desired to alter the initially set heating time after observing the state of the food being cooked during the interruption, the user must depress a clear key, store the new cooking conditions by setting the new desired heating time with the heating time setting key and the desired output power level and the like using function keys and thereafter depress the start key. For elaborate cooking, the conventional microwave oven thus requires a complex procedure, which entails a time loss and also manipulation errors when food is to be cooked quickly. 
     SUMMARY OF THE INVENTION 
     With reference to FIG. 1 which is a block diagram showing the construction of a microwave oven of the present invention, the oven comprises a heating chamber 1 having a door, high-frequency heating means 2 for heating food, detecting means 3 for detecting the opening and closing of the door, a plurality of setting keys 4 mounted on the front side of the door for setting the heating time, timer means 5 for measuring the time set by the setting key and for driving the high-frequency heating means 2 during its operation, start means 6 for initiating the timer means 5 into a time measuring operation at the end of a predetermined period of time after the depression of the setting key, stop means 7 for temporarily suspending the operation of the timer means 5 in response to an output from the detecting means 3 the cooking is interrupted by opening the door, and control means 8 for causing the timer means 5 to measure the rest of the heating time when one of the setting key 4 corresponding to the setting key 4 initially used for setting the heating time is despressed within a specified period of time after the door is closed to resume cooking, or for setting a new desired heating time or for adding a time interval corresponding to the other setting keys when said other keys are alternatively depressed, or for resetting the timer means 5 when none of the setting keys 4 are depressed. 
     According to the present invention, the start means 6 instructs the timer means 5 to start heating upon lapse of the predetermined period of time after the depression of the setting key 4, so that the start key of the conventional microwave oven can be dispensed with. This serves to reduce the number of setting keys 4 needed for setting cooking conditions, diminishing the space needed for the control panel to render the main body of the microwave oven compact and making the oven easy to operate. 
     Since the control means 8 has stored within it the conditions for cooking the food being treated even when the door is opened during cooking, the interrupted cooking operation can be continued by simple manipulation of the setting key 4. 
     When the state of the food being cooked is observed during the interruption, the subsequent heating time can be adjusted to a period different from the initially set heating time by manipulating the setting key 4. 
     It is desirable to provide display means in the vicinity of the setting keys 4 for indicating the heating time to be set by the setting key. Also, the setting key 4 preferably comprises a push-button switch or membrane switch. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing the basic construction of microwave ovens of the invention; 
     FIG. 2 is a perspective view showing the appearance of a microwave oven embodying the invention; 
     FIG. 3 is a front view showing an operation panel provided on the outer side of the door of the microwave oven shown in FIG. 2; 
     FIG. 4 is a block diagram showing the construction of the embodiment; 
     FIGS. 5(a)-5(c) are flow charts for illustrating the operation of the embodiment; and 
     FIG. 6 is a front view showing another example of control panel for the embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of the present invention will be described below with reference to the drawings. 
     FIG. 2 shows the appearance of a microwave oven embodying the invention. With reference to this drawing, reference 20 is the main body of the oven. A heating chamber 21 is provided within the main body 20 for accommodating the article to be heated. Within the heating chamber 21, high-frequency electromagnetic waves are emitted by a magnetron (not shown) serving as heating means. Food (not shown) as the article to be heated is heated by the electromagnetic wave. 
     The heating chamber 21 has a front opening which comprising a door 23 having a transparent panel 22. Mounted on the inner wall of the door 23 are latch heads 24 each engageable with or disengageable from a latch hook 25 mounted to the flange of the main body 20 when the door 23 is closed or opened, respectively. The latch head 24 and the latch hook 25 are operatively connected to a switch, (not shown) thereby serving as means for detecting the opening and closing of the door 23. 
     FIG. 3 is a front view showing an operation panel provided on the outer wall of the door 23. References 30a through 30d are a plurality of keys for setting cooking conditions. These keys include &#34;REHEAT ROLL&#34; key 30a for providing an output of 20-seconds of heating time when depressed once, &#34;REHEAT PLATE&#34; key 30b for providing heating time of 30 minutes and 30 seconds when depressed once, &#34;BAKED POTATO&#34; key 30c for causing an output of 6-minutes of heating time when depressed once, and &#34;FROZEN ENTREE&#34; key 30d for providing an output of 10-minutes of heating time when depressed once. Each of these keys 30a to 30d is preset to the specified heating time. On the other hand, setting keys 30e and 30f are provided for the user to set optional periods of heating time different from those set by the above setting keys 30a to 30d. The key 30e is &#34;1 MIN&#34; key by which 1-minute heating time is settable when it is depressed once. When the key 30e is depressed repeatedly, the heating time is increased by 1 minute increments relating to the number of times it is depressed. The key 30f is &#34;10 SEC&#34; key for setting heating time in 10-second units in the same manner as the 1 MIN key. When successively depressed, 1 MIN key increases the heating time by increments of 1 minute, and 10 SEC key by increments of 10 seconds. When 1 MIN key and 10 SEC key are used in combination, heating time is settable in minute and 10 second units. 
     References 31 and 32 are function keys. The key 31 is &#34;CLOCK/CLEAR&#34; key for causing the LCD readout, described below, to indicate the time of day and also for canceling an erroneous set heating time. The key 32 is &#34;DEFROST&#34; key for lowering the output power level to 30%. Reference 33 is the above-mentioned LCD readout which usually provides a clock display while the power supply is on. On depression of the setting key 30, the readout indicates the set heating time. 
     FIG. 4 is a block diagram showing the construction of the present embodiment. 
     Depression of any one of the plurality of setting keys 30 is detected by a key input detecting circuit 40 which feeds the key input is fed to a control circuit 41. The control circuit 41, which comprises a microcomputer, actuates a one-second timer 42a serving as first timer means for measuring a first predetermined time interval every time one of the setting keys 30 is depressed. When one of the setting keys 30 is depressed consecutively during the operation of the one-second timer 42a, the depression of one of the setting keys 30 causes the control circuit 41 to regard the inputs of the depressed setting keys 30 as effective and consecutively adds the periods of time represented by these setting keys 30 to calculate the desired heating time while at the same time resetting and starting the one-second 42a timer again in response to every input of the setting key. When the operation of the one-second timer 42a is completed after the depression of the final time setting key 30, the setting procedure is regarded as completed, whereupon the control circuit 41 stores the overall heating time entered and the kind of keys depressed 30 in a memory 43, sets the overall heating time in a heating timer 44 and actuates this timer 44. During the operation of the microwave oven, the heating timer 44 operates a magnetron 46 through a heating control circuit 45. Reference 42b is a 0.5-second timer operative when the 1 MIN key or 10 SEC key is held depressed. Completion of the operation of the magnetron 46 is detected by a heating completion detecting circuit 47, and a message to this effect is sent to the control circuit 41. Upon opening or closing the door 23, a door switch 48 produces a signal, which is then checked by a door opening-closing detecting circuit 49 as to whether the signal represents opening or closing. The result is sent to the control circuit 41. When the door opening-closing detecting circuit 49 detects that the door 23 is in its closed position, the control circuit 41 actuates a one-minute timer 50 serving as second timer means for measuring a second predetermined time interval. A buzzer 51 is turned on by a buzzer control circuit 52 to produce a sound signal, for example, when the setting key 30 is depressed properly or on completion of operation of the heating timer 44. Reference 53 is a power supply circuit for operating the system shown in FIG. 4, reference 54 is a circuit for detecting that the power supply is on, and reference 55 is a ROM that stores a program for controlling the control circuit 41. The circuit 41 executes a control process according to this program. 
     FIGS. 5(a)-(c) are flow charts showing the program stored in the ROM 55. 
     First, inquiries are made in succession as to whether the power supply is on (step 60), whether the door is closed (step 61), whether cooking is completed (step 62) and whether CLEAR key is depressed (step 63). When these inquires (steps 60 to 63) are answered in the affirmative, the one-minute timer 50 is actuated to count up 1 minute (step 64). With the start of the counting, step 65 checks whether 1 minute has elapsed. Step 67 checks whether one of the setting keys 30a to 30d is depressed within the 1 minute period (steps 66, 67). If the lapse of 1 minute is detected in step 65, the cooking data is erased (step 101), and the sequence returns to step 60. This eliminates the likelihood that the control circuit 41 will be operated when the setting key 30 is inadvertently depressed, thus assuring safety. When the inquiry of step 67 is answered in the negative, 1 MIN key 30e and 10 SEC key 30f are checked as to whether they are depressed (steps 68, 69). If 1 MIN key 30e is depressed, one-minute heating time is set (step 70). When 10 SEC key 30f is depressed, 10-second heating time is set (step 71). Subsequently, the timers 42b and 42a are set to 0.5 second and 1 second, respectively, in succession (steps 72, 73). Step 74 checks whether 1 MIN key 30e or 10 SEC key 30f has been released. Upon the lapse of 1 second after the release of the key, cooking is started (steps 75, 76, 77). If the door is opened during cooking, or the cooking is completed (steps 78, 79), the cooking data is cleared (step 101). When 1 MIN key 30e or 10 SEC key 30f is held depressed in step 74 for less than 0.5 second (steps 80, 81), step 73 follows. When the duration of depression is longer, the heating time to be set by the depressed key is added to the initial heating time upon lapse of every 0.5 second (steps 82→83→73→74→80→81→82). Further when step 75 detects that the one-second timer 42a has not reached 1 second, step 84 checks again whether the setting key 30e or 30f is in a depressed position. When the answer is in the affirmative, the heating time to be set by the key 30e or 30f concerned is added the number of time the key has been depressed (step 85) aside from the foregoing step following the continued depression of the key 30e or 30f. 
     The depression of one of the setting keys 30a to 30d in step 67 is followed by step 86 in which the predetermined heating time is set. The one-second timer 42a is then actuated in step 87. After detecting that 1 second has elapsed since the depressed key was released, cooking is started (steps 88, 89). Cooking (step 90) is then checked as to its completion (step 91). If the door is not opened at this time, cooking will be continued, whereas if the door is opened, the cooking operation is discontinued (steps 92, 93). If the cooking operation is interrupted for at least 1 minute, the one-minute timer 50 is set in step 94 to terminate the operation. Step 95 inquires whether the door is closed. With closing of the door, the one-minute timer 50 starts counting. Before one minute elapses (step 96), step 97 inquires whether a setting key has been depressed. If the answer is affirmative, step 98 checks whether the depressed key is the same as the setting key depressed for setting the initial heating time. When the answer to the inquiry is &#34;YES,&#34; cooking is resumed for the rest of heating time (step 99), followed by step 90. If the depressed key is determined to be different in step 98 from the key depressed for setting the initial heating time, the sequence returns to step 86 in which a new heating time is set. On completion of cooking (step 100), the cooking data is cleared (step 101), followed by step 60. 
     Thus according to the present invention, no start key is need, thereby decreasing the number of keys for setting cooking conditions, rendering the oven easy to operate, diminishing the space needed for the operation assembly and thereby making the oven main body compact. Further because the settings for cooking remain without clearing even when the door is opened during cooking, the cooking operation can be resumed after an interruption by a simple procedure. The conditions set for cooking can be changed before resuming the cooking operation, so that it is possible to recognize the state of the food being cooked by opening the door during cooking and to set suitable conditions for the subsequent cooking operation based on the result. 
     FIG. 6 shows another embodiment of operation panel which has a plurality of setting keys 110 in the form of push buttons for setting cooking conditions. These keys include &#34;REHEAT ROLL&#34; key 111, &#34;REHEAT PLATE OF LEFTOVERS&#34; key 112, &#34;BAKED POTATO&#34; key 113 and &#34;FROZEN ENTREE&#34; key 114 which are preset to heating periods of 20 seconds, 3.5 minutes, 6 minutes and 10 minutes, respectively. Indicated at 115 is &#34;ONE MINUTE&#34; key for the user to set the desired heating time. This key is adapted to set one-minute heating time when depressed once.