Convection Cooking System; Damper Open-Close Mechanism; Microwave Cooking; Damper Operation - Sharp R-9H10 Service Manual

R-9HlO
CONVECTION COOKING SYSTEM
This oven is designed with a hot air heating system
where food is not directly heated by the convection
heater, but is heated by forced circulation of the hot
air produced by the convection heater.
The air heated by the convection heater is circulated
through the convection passage provided on the outer
casing of the oven cavity by means of the convection
fan which is driven by the convection motor. It then
enters the inside of the oven through the vent holes
provided on the left side of the oven. Next,the hot air
heats the food on the turntable and leaves the oven
cavity through the vent in the oven cavity left side wall.
Without leaving the oven, this hot air is reheated by the
convection heater, passes through the convection
passage and enters the inside of the oven cavity again,
in a continuing cycle.
In this way, the hot air circulates inside the oven cavity
to raise its temperature and, at the same time, comes
into contact with the food being cooked.
When the temperature inside the oven cavity reaches
the selected temperature, the convection heater is
de-energized. When the temperature inside ihe oven
cavity drops below the selected temperature, the con-
vection heater is energized again. In this way, the in-
side of the oven cavity is maintained at approximately
the selected temperature.
When the convection time reaches 0, the convection
heater is deenergzed and the convection fan stops op-
erating and the oven shutts off.
Upon completion of the cooking time, the audible sig-
nal will sound, and oven lamp, turntable motor, cooling
fan motor and convection motor are de-energized. At
the end of the convection cycle, if the cavity air tem-
perature is above 90 "C., the circuit to RY6 will be
maintained (by the thermistor circuit) to continue op-
eration of the cooling fan motor until the temperature
drops below 90 OC., at which time the relay will be
de-en !rgized, turning off the fan motor. Relay RY5 will
howe? er, open as soon as the convection cycle has
ended, turning off the convection fan motor.This will
now cool and allow t!, damper door to open.
(RD72NOl U')
DAMPER OPEN-CLOSE MECHANISM
Usually, the damper is in the open position except
during convection cooking.
Damper position is set automatically by damper motor,
damper switch, motor cam and damper shaft..
These components are operated by a signal that judges
if microwave cooking or convection cooking operation
is selected by the CPU unit,
Microwave Cooking:
Damper is in the open position, because a portion of
cooling air is channeled through the cavity to remove
steam and vapors given off from the heating foods.
It is then exhausted at the top of the oven cavity into
a condensation compartment.
Convection Cooking:
Damper is in the closed position, so that no hot air will
be allowed to leak out the oven cavity.
Damper Operation
1. When power supply cord is plugged in:
1-I. When power supply cord is plugged in, a sig-
1-2
1-3
1-4
1-5.
nal is sensed in the control unit, and operates
shut'-off relay (RY4).
Contacts of shut-off relay (RY4) close, the
damper motor is energized, opening the
damper door.
When the damper is moved to the open posi-
tion by the damper cam, damper switch is
closed (ON position).
The signal of damper switch is re-sensed in
the control unit and shut-off relay (RY4) is
turned off.
The 240 volts A.C. to the damper motor is
stopped and the motor turns off.
2. When oven is microwave cooking:
Damper is in the open position.
3. When oven is convection cooking:
3-l.
3-2.
3-3.
3-4
NOTE:
Damper motor is energized by touching the
convection, temperature and START pads.
When damper is in the closed position
(damper switch is OFF), its signal is sensed
by the control unit, and shut-off relay (RY4)
is de-energized.
The damper is held in the closed position
during the convection cooking operation.
At the end of the convection cooking, shut-off
relay (RY4) is energized, and the damper is
returned to the open position.
If the damper door is not in the proper position,
closed durin convection or open durning
microwave, the control unit will stop oven op-
eration after 1 minute.
Cooking Mode Operation of Damper
Microwave cooking OPEN
Convection cooking CLOSE
Sensor cooking OPEN
Automatic mix cooking
CLOSE
Grill cooking CLOSE
Slow cookina CLOSE
(RD72002U)
DAMPER SHAFT
DAMPER DUCT
DAMPER CAM
DAMPER SWITCH
DAMPER MOTOR
Figure D-l. Damper Mechanism
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