Electric heating – Microwave heating – With control system
Reexamination Certificate
2000-01-11
2001-07-31
Hoang, Tu Ba (Department: 3742)
Electric heating
Microwave heating
With control system
C219S704000, C219S748000
Reexamination Certificate
active
06268597
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a microwave oven having a stationary wave magnetic field detecting device.
2. Description of the Prior Art
Generally, a microwave oven cooks food by using microwaves, and the intensity of the microwaves generated from a magnetron of the microwave oven is varied in accordance with characteristics of the cooked food. That is, various factors of the food such as material, shape, etc. of the food determine microwave absorption and the magnitude of microwave energy. Accordingly, the microwave oven usually performs the cooking operation after analyzing the status of the food by various sensors.
FIG. 1
schematically shows a magnetic fluid detecting device of a conventional microwave oven.
As shown in
FIG. 1
, the conventional microwave oven includes a magnetron MGT for generating microwaves of approximately 2450 MHz, a waveguide
10
for transmitting the microwaves generated from the magnetron MGT into a food
11
in a cooking chamber
2
, and a magnetic field detecting device
100
for detecting the cooking status of the food
11
by receiving electromagnetic waves reflected through the waveguide
10
.
The magnetic field detecting device
100
includes an antenna sensor
101
, a diode D, and a shield member
120
. The antenna sensor
101
, the diode D, and the shield member
120
are fixed on a wall of the waveguide
10
, in a manner that the antenna sensor
101
is protruded inside the waveguide
10
.
The diode D is connected with an end of the antenna sensor
101
, to apply the detected voltage of the stationary wave received from the antenna sensor
101
to a microcomputer
130
, and the microcomputer
130
determines the cooking status of the food
11
by the detected voltage of the stationary wave received through the diode D.
FIG. 2
is a view for explaining the operating principle of a conventional magnetic field detecting device. As shown in
FIG. 2
, the end of the antenna sensor
101
is grounded on an inner wall of the waveguide
10
by welding, and has 0 (zero) degree of electric potential, while another end of the antenna sensor
101
is connected with the diode D through an inserting hole
10
a
of the waveguide
10
.
Further, in order to have a predetermined sectional area A between the waveguide
10
and the antenna sensor
101
, a certain portion of the antenna sensor
101
forms a semicircular loop. Through the predetermined sectional area A formed in the loop of the antenna sensor
101
, a magnetic flux, which is formed by the stationary wave reflected into the waveguide, passes.
Meanwhile, the microwaves generated from the magnetron MGT are radiated in the form of an electromagnetic wave, and the combination of the microwaves advancing into the cooking chamber
2
from the waveguide
10
, and the microwaves reflected from the cooking chamber
2
into the waveguide
10
forms the stationary wave in the waveguide
10
.
Here, the voltage is induced from the antenna sensor
101
as follows: When the magnetic flux formed by the stationary wave in the waveguide
10
passes through a predetermined sectional area A formed between the waveguide
10
and the antenna sensor
101
, the magnetic flux density B generated in the loop in the antenna sensor
101
is obtained by the following formula 1:
B=/A (1)
Further, the electromagnetic wave is a function of time, and the magnetic flux density B induced at the sectional area A in the antenna sensor
101
is accordingly varied in magnitude in accordance with the time. Accordingly, by the Maxwell equation, the voltage induced to the antenna sensor
101
can be obtained by the following formula 2:
E=−dB/dt (2)
FIG. 3
shows a voltage switching section of the magnetic field detecting device shown in FIG.
1
. As shown in
FIG. 3
, an anode of the diode D is connected to the antenna sensor
101
, and a cathode of the diode D is connected with an electrolytic capacitor C being connected in parallel relation with a resistor R, forming a closed circuit.
The diode D detects the voltage in accordance with the stationary wave of the antenna sensor
101
, and the electrolytic capacitor C smooths the detected voltage into a predetermined voltage which is outputted as an output voltage Vout by a voltage drop generated at both ends of the resistor R.
By employing the magnetic field detecting device having such an antenna sensor, the conventional microwave is enabled to adjust to the various cooking environments which are varied in accordance with the shape or material of the food when cooking the food, so that the detection error of the sensor is reduced and the cooking status of the food is precisely detected.
The antenna sensor of the magnetic field detecting device employed in the conventional microwave oven, however, has a problem as follows. As shown in
FIG. 2
, one end of the antenna sensor is grounded on the inner wall of the waveguide by welding, while the other end thereof is connected with the diode, the electrolytic capacitor and the resistor, respectively, by being extended outside the waveguide, to be connected with an input wire. Accordingly, various processes such as a process of fixing the antenna sensor, a process of connecting respective circuit elements to the antenna sensor, etc., need to be performed repetitiously. As a result, the working process becomes complicated, disturbing the automation or mass-production of the microwave oven, and deteriorating the productivity.
Further, in the microwave oven having the conventional magnetic field detecting device, the antenna sensor fixing locations can not be precisely controlled with respect to the waveguide, so that there are uneven sectional areas formed in the loops of the antenna sensors, and the exact voltage value can not be detected by the antenna sensor.
Further, the fixed portion of the antenna sensor fixed on the wall of the waveguide by welding is chemically deformed or snapped off by the long and repetitious use thereof, resulting in a deteriorated reliability about the detected stationary wave data.
SUMMARY OF THE INVENTION
The present invention has been developed to overcome the above-mentioned problems of the prior art, and accordingly, it is an object of the present invention to provide a microwave oven having improved reliability about detected data by an improvement in an antenna sensor structure and an installation of a magnetic field detecting device.
The above object is accomplished by a microwave oven according to the present invention, including an antenna sensor having a loop portion which is protruded into a waveguide of the microwave oven, and a wire whose one end is grounded at the waveguide, wherein the wire of the antenna sensor is grounded at an outer side of the waveguide.
Preferably, the microwave oven according to the present invention further comprises a shield member for fixing the antenna sensor in a manner that the loop portion of the antenna portion is protruded into the waveguide, and for fixing one end of the wire in a manner that the one end of the wire is grounded at the outer side of the waveguide.
The shield member includes a projection for fixedly supporting the loop portion of the antenna sensor, and is formed of a case body in which a magnetic field voltage detecting circuit element is received and is processed by molding.
Further, the waveguide includes an inserting hole into which the antenna sensor is received, and the antenna sensor includes a neck portion which is fixed in the inserting hole of the waveguide. Also, the microwave oven according to the present invention further includes a shield member having a hole formed thereon for supporting the neck portion of the antenna sensor.
Further, the microwave oven according to the present invention further includes a printed circuit board for fixing the antenna sensor in a manner that the loop portion of the antenna sensor is protruded into the waveguide, and for fixing the wire by grounding the wire. The printed circuit board includes a screw hole
Jang Bo-in
Jeong Joon-young
Lee Won-woo
Lim Dong-Bin
Park Tae-soo
Bushnell , Esq. Robert E.
Hoang Tu Ba
Samsung Electronics Co,. Ltd.
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