Microwave oven waveguide with microwaves sensor

Abstract: A microwave oven has a sensing probe (101) in its waveguide (10) for sensing microwaves. The probe (101) is connected to a diode (D). If the diode (D) fails, going short-circuit, a magnetron failure may be falsely detected. To solve this problem, a test pulse is applied to the output side of the diode (D). If this pulse is detectable, the diode (D) has not failed. However, if the diode (D) has failed, the pulse will be shunted to chassis via the probe (101) and will not be detectable.

Description: The present invention relates, in a first aspect, to a microwave oven comprising a waveguide for conducting microwaves to a cooking chamber and a sensor for sensing microwaves in the waveguide, the sensor comprising a grounded sensing probe in the waveguide and a diode connected between the probe and an input of a voltage detecting means. The present invention also relates, in a second aspect, to a microwave oven comprising a waveguide, a magnetron for generating and supplying microwaves into the waveguide, a control panel having a plurality of input buttons for setting data for cooking conditions, cooking menus, or the like, a sensor for sensing microwaves in the waveguide and outputting a voltage in accordance with the presence or absence of microwaves in the waveguide, a display section by which the operational status of the microwave oven is displayed and a microcomputer having an input connected to receive the output of the sensor. Figure 1 is a partially cut away perspective view of a conventional microwave oven. As shown in Figure 1, a door 4 is pivotably fixed to the front of a body 1 for opening and closing a cooking chamber 2. A turntable 5 is located at the bottom of the cooking chamber 2 and food to be cooked is placed on the turntable 5. A control panel 7, including a keypad, is mounted on one side of the front of body 1. An air guide 8 and a cooling fan 9 are located in an component chamber 3 behind the control panel 7. A magnetron MGT is also housed in the component chamber 3. The air flow created by the fan 9 is guided by an air guide 8 and cools the component chamber 3 A user controls the operation of the microwave oven by means of various buttons on the control panel 7. The control panel 7 has a display 7A which displays data input using the keypad buttons, the operational status of the microwave oven, messages, etc. Figure 2 shows a microwave detecting device of a conventional microwave oven and Figure 3 shows the circuit of the detecting device of Figure 2. Referring to Figures 2 and 3, a diode D is connected between a sensor loop 101 in a waveguide 10 and an input P 1 of a microcomputer 130. A resistor R, a capacitor C and a Zener diode ZD are connected in parallel between the input P 1 and chassis. The sensor loop 101 extends out of the waveguide 10 via a grommet 120. A shield member 100 surrounds the diode D, the resistor R, the capacitor C and the Zener diode ZD. Microwaves propagating along the waveguide 10 induce a voltage across the sensor loop 101. The voltage induced across the sensor loop 101 is rectified and smoothed by the diode D and the capacitor C. The voltage thus appearing across the resistor R is input into the microcomputer 130. The Zener diode ZD limits the voltage that can be input to the microcomputer 130 in order to protect the microcomputer 130. A microwave oven according to the first aspect of the present invention is characterised by test means configured for applying a test voltage at the end of the diode connected to the input of the voltage detecting means, the polarity of said voltage being suitable for reverse biasing said diode. A capacitor and a resistor connected in parallel may be included between said input and ground. Preferably, the test means is configured to produce said test voltage in the form of a pulse. Preferably, the voltage detecting means and the test means comprise a microprocessor. More preferably, the microprocessor is programmed to generate the test voltage after detecting 0V, i.e. a no microwaves signal voltage, in its role as voltage detecting means. Conveniently, manually operable test trigger means, e.g. a push button, is provided and the test means is responsive to operation of the test trigger means to generate said test voltage. A microwave oven according to the second aspect of the present invention is characterised in that the microcomputer is configured to respond to the reception of a predetermined voltage level from said sensor by: outputting a test voltage to the sensor, detecting the voltage at said input resulting from the outputting of said test voltage, and causing the display section to display the operational status of said sensor in accordance with the voltage detected at said input resulting from the outputting of said test voltage. Preferably, said sensor comprises a diode, the diode being connected between the waveguide and said input of the microcomputer with its cathode connected to said input. More preferably, the microcomputer is configured to cause the display section to display the operational status of the diode. Preferably, the microcomputer is configured to output said test voltage in the form of a pulse. Preferably, the oven includes a resistor connected such that the test voltage is applied to said input therethrough. More preferably, the microcomputer is configured such that said test voltage is applied to said input at a predetermined time interval. Still, more preferably, the predetermined time interval is thirty seconds. Preferably, the oven further comprises a check button means for applying a check signal to the microcomputer, wherein the microcomputer is configured to output said test voltage in response to inputting of said check signal. More preferably, the check button means is formed on the control panel. Yet more preferably, the check button means is the combination of a plurality of input buttons. Embodiments of the present invention will now be described, by way of example, with reference to Figure 4 to 7 of the accompanying drawings, in which: - Figure 1 is a partially cut away perspective view of a conventional microwave oven; Figure 2 is schematic seectional view of the microwave oven of Figure 1; Figure 3 is a circuit diagram of the microwave detecting device of Figure 2; Figure 4 is a circuit diagram of a first microwave detecting device according to the present invention; Figure 5 is a flow chart illustrating the operation of the microwave oven having the circuit of Figure 4; Figure 6 is a circuit diagram of a second microwave detecting device according to the present invention; and Figure 7 is a flow chart illustrating the operation of the microwave oven having the circuit of Figure 6; Referring to Figure 4, a microwave detecting device 40 includes a microwave detecting section, a resistor R 1 , a display section 7A, and a microcomputer 135. The microwave detecting section includes a diode D which is connected between one end of the sensing loop 101 in the waveguide 10 and a first port P 1 of the microcomputer 135. The diode's cathode is connected to the first port P 1 . The other end of the sensing loop 101 is grounded to the wall of the waveguide 10. The resistor R, the capacitor C, and the Zener diode ZD are connected in parallel with each other between the cathode of the diode D and chassis/ground. The resistor R, the capacitor C, and the Zener diode ZD keep uniform output of the diode sensor D. The resistor R1 is connected between the first and second ports P 1 and P 2 of the microcomputer 135. The microcomputer 135 is also connected to the display section 7A. The display section 7A may be provided on the control panel 7 or separately on the front of the microwave oven. Referring to Figure 5, after placing food to be cooked on the turntable 5, the user pushes a start button (not shown) on the control panel 7, and the magnetron MGT of the microwave oven starts its operation. In this situation, the microcomputer 135 detects the voltage output by the microwave detecting section. In other words, as the magnetron MGT operates, microwaves are generated and propagate to the cooking chamber 2 through the waveguide 10. The high-frequency magnetic field in the waveguide 10 induces a voltage across the sensing loop 101. The induced voltage is rectified by the diode D and smoothed by the capacitor C/resistor R combination. However, if the magnetron MGT is not operating normally and the magnetic field is not formed in the waveguide 10, no voltage is induced across the sensing loop 101. Consequently, 0V is output. The 0V signal is input to the first port P 1 of the microcomputer 135. When the 0V signal is input to the first port P1, the microcomputer 135 displays a magnetron error message using the display section 7A. However, if a non-0V signal is input to the first port P1, the microcomputer 135 carries out a main algorithm. When a 0V signal is input to the first port P1, the microcomputer 135 generates a voltage pulse from the second port P 2 of the microcomputer 135. The voltage pulse of the second port P 2 is detected at the first port P 1 of the microcomputer 135 through the resistor R1. If the pulse voltage is detected at the first port P 1 of the microcomputer 135, the microcomputer 135 displays a message indicating normal status of the sensor diode D, such as "diode sensor normal", or the like, using the display section 7A. If, however, the voltage pulse is not detected at the first port P 1 of the microcomputer 135, the microcomputer displays a message indicating an abnormality of the diode D, such as "diode sensor abnormal", or the like, using the display section 7A. During the cooking operation of the microwave oven, the microcomputer 135 detects the operation of the magnetron MGT and the diode D at predetermine time intervals, such as thirty (30) second intervals, or the like. Referring to Figure 6, a check button 42 is connected to a third port P 3 of the microcomputer 135. The check button 42 may be added to the conventional control panel 7 (See Figures 1 and 3), which has a plurality of input buttons, or may be the combination of a plurality of input buttons. Referring to Figure 7, when the microwave oven is turned on, the microcomputer 135 determines if the check button 42 is being pushed (Step S1). If the check button 42 is not pushed, the microcomputer 135 carries out the usual main algorithm. However, if the check button 42 is being pushed, signal corresponding thereto is input at a third port P 3 of the microcomputer 135. As the signal is being input at the third port P 3 , the microcomputer 135 outputs a voltage pulse of, for example 5V, from the second port P 2 (Step S2). In this situation, if the diode D is normal, the pulse voltage is input at the first port P 1 of the microcomputer 135 through the resistor R 1 . However, if the diode D is broken and short-circuited, the voltage at the first port P 1 remains 0V because the first port P 1 is grounded through the sensor loop. If the voltage pulse is detected at the first port P 1 , then the microcomputer 135 displays a message indicating normal status of the diode sensor, such as "diode sensor normal", etc., using the display section 7A (Step S4). If the voltage pulse is not detected at the first port P 1 , the microcomputer 135 displays a message indicating abnormal status of the diode D such as "diode sensor abnormal" through the display section 7A (Step S5). As described above, in the microwave oven according to the present invention, the microcomputer detects not only microwaves in the waveguide, but also the presence of an abnormality in the diode, and when an abnormality occurs in the microwave oven, it is displayed using the display section by indicating whether the abnormality of the microwave oven is due to the magnetron or the diode sensor.

Claims: A microwave oven comprising a waveguide (10) for conducting microwaves to a cooking chamber (2) and a sensor for sensing microwaves in the waveguide, the sensor comprising a grounded sensing probe (101) in the waveguide (10) and a diode (D) connected between the probe (101) and an input (P 1 ) of a voltage detecting means (130), characterised by test means (130, R 1 ) configured for applying a test voltage at the end of the diode (D) connected to the input (P 1 ) of the voltage detecting means (130), the polarity of said voltage being suitable for reverse biasing said diode (D). A microwave oven according to claim 1, including a capacitor (C) and a resistor (R) connected in parallel between said input (P 1 ) and ground. A microwave oven according to claim 1 or 2, wherein the test means (130) is configured to produce said test voltage in the form of a pulse. A microwave oven according to claim 1, 2 or 3, wherein the voltage detecting means and the test means comprise a microprocessor (130). A microwave oven according to claim 4, wherein the microprocessor (130) is configured to generate the test voltage after detecting 0V in its role as voltage detecting means. A microwave oven according to any preceding claim, including manually operable test trigger means (42), wherein the test means (130) is responsive to operation of the test trigger means to generate said test voltage. A microwave oven comprising: a waveguide (10); a magnetron for generating and supplying microwaves into the waveguide (10); a control panel (7) having a plurality of input buttons for setting data for cooking conditions, cooking menus, or the like; a sensor for sensing microwaves in the waveguide and outputting a voltage in accordance with the presence or absence of microwaves in the waveguide; a display section (7A) by which the operational status of the microwave oven is displayed; and a microcomputer (135) having an input (P 1 ) connected to receive the output of the sensor, characterised in that the microcomputer (135) is configured to respond to the reception of a predetermined voltage level from said sensor by: outputting a test voltage to the sensor, detecting the voltage at said input (P 1 ) resulting from the outputting of said test voltage, and causing the display section (7A) to display the operational status of said sensor in accordance with the voltage detected at said input (P 1 ) resulting from the outputting of said test voltage. A microwave oven according to claim 7, wherein said sensor comprises a diode (D), the diode (D) being connected between the waveguide (10) and said input (P 1 ) of the microcomputer (135) with its cathode connected to said input (P 1 ). A microwave oven according to claim 8, wherein the microcomputer (135) is configured to cause the display section to display the operational status of the diode (D). A microwave oven according to claim 7, wherein the microcomputer (135) is configured to output said test voltage in the form of a pulse. A microwave oven according to claim 7, including a resistor (R 1 ) connected such that the test voltage is applied to said input (P 1 ) therethrough. A microwave oven according to claim 11, wherein the microcomputer (135) is configured such that said test voltage is applied to said input (P 1 ) at a predetermined time interval. A microwave oven according to claim 12, wherein the predetermined time interval is thirty seconds. A microwave oven according to claim 7, further comprising a check button means (42) for applying a check signal to the microcomputer (135), wherein the microcomputer (135) is configured to output said test voltage in response to inputting of said check signal. A microwave oven according to claim 14, wherein the check button means (42) is formed on the control panel (7). A microwave oven according to claim 14, wherein the check button means (42) is the combination of a plurality of input buttons.

Inventors: HA JAE-KI, HA, JAE-KI
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO., LTD.
Application year: 1999
Main classification: H05B6
IPC codes: H05B6, F24C7