Rice cooker development history

The main structure of an ordinary rice cooker is composed of a heating plate, a temperature limiter, a heat preservation switch, a lever switch, a current-limiting resistor, an indicator light, and a socket.

Heating plate

This is the main heating element of the rice cooker. It is an aluminum alloy disc with an embedded electric heating tube. The inner pot is placed on it and you can see it after removing the inner pot.

Temperature limiter

Also called magnet. It is equipped with a permanent magnetic ring and a spring, which can be pressed, and the position is in the center of the heating plate. When cooking rice, when the rice cooking switch is pressed, the lever switch is driven by the suction force of the magnet to keep the power contacts on. When the rice is cooked, the temperature of the bottom of the pot increases continuously, and the suction force of the permanent magnetic ring increases with the temperature. However, when the water in the inner pot is evaporated and the temperature of the bottom of the pot reaches 103 ± 2℃, the suction force of the magnetic ring is less than the elastic force of the spring on it, and the temperature limiter is pushed down by the spring, which drives the lever switch to cut off the power. .

Keep warm switch

Also known as thermostat. It is composed of a spring leaf, a pair of normally closed contacts, a pair of normally open contacts, and a bimetallic sheet. When the rice is cooked, the temperature in the pot rises. As the thermal expansion and contraction rates of the two metal sheets forming the bimetallic sheet are different, the bimetallic sheet is bent upward as a result. When the temperature reaches above 80°C, under the push of the upwardly bent bimetal, the spring plate drives the normally open and normally closed contacts to switch, thereby cutting off the power supply of the heating tube and stopping heating. When the temperature in the pot drops below 80°C, the bimetallic sheet gradually cools and recovers, the normally open and normally closed contacts are switched again, and the heating tube is switched on for heating. This is repeated to achieve the heat preservation effect.

Lever switch

The switch is completely mechanical and has a normally open contact. When cooking rice, press this switch to power on the heating tube and at the same time power the heating indicator light to light it. When the meal is ready, the temperature limiter pops down and drives the lever switch to disconnect the contacts. After that, the heating tube is only controlled by the heat preservation switch.

Current limiting resistor

The appearance is mostly golden or white, and the size is like a 3W resistor. It is pressed between the heating tube and the power source to protect the heating tube. The commonly used current limiting resistor is 185C 5A or 10A (depending on the power of the rice cooker). The current-limiting resistor is a key element to protect the heating tube and cannot be replaced by a wire.