What is a thermostat?


● • Themostat
 A device that stabilizes heat and temperature
The etymology for thermostat is a compound word combining “thermo” which means temperature or heat, and “stat” which means a stationary state. “Thermo” is how the word is pronounced in English, but in German it is pronounced “terumo” or “tamu”.
● • Purpose
(1) Temperature regulator (controller): Maintains a certain degree of temperature.

(2) Excess temperature rise protector (limiter/protector): Turns off the heat source when the temperature rises above a particular level.

(3) Temperature detector: Signals when the set temperature has been reached and causes another operation to occur.
These are the main purposes of the thermostat.

● • Asahi’s Thermostat is a bimetal thermostat.
 The temperature switch senses the temperature through the bimetal and controls the electricity contacts (turning them on or off).
There are various kinds of devices for temperature control and measurement.


What are the principles of bimetal?

● • Bimetal Two metals (a low expansion metal and a high expansion metal) are milled into a single sheet using a roller → Bimetal
● • Bimetal is a compound word combining “bi” (a prefix meaning “two”) and “metal.”
● • Pressurized bonding Bonding by cool or hot rolling (molecular bonding). No adhesive is used.
● • Materials High expansion metal contains an iron alloy (Fe) and nickel (Ni) with added substances Cr, Mn, and Mg; low expansion metal contains iron (Fe) and nickel (Ni) as the main materials for Invar (Ni35-Fe)
● • Bimetal bends in one direction as the temperature rises and in the other direction as it falls.
● • Force arises where the movement is controlled, and in the thermostat the set point pressure exerts a repelling force.

Structure and mechanism of the thermostat US-622 ON・OFF


Types, structures and purposes of bimetal thermostats

● • Types and structures

PLaminated type In this type, parts have been laminated together and fastened with a rivet, facilitating temperature variations in small increments.
Snap disc type In this type, parts are contained in a covered case. It has a relatively large differential, and uses a low cost snap disc to prevent excessive temperature rises.
Protector type This type is contained in a covered case, with, a snap disc integrated into the electric circuit for the detection and prevention of temperature rises or overcurrent situations.

● • Applications

Home electric appliances Home electric appliances: Kitchen goods (Computerized hot water kettles, coffee makers, ovens, hot plates, rice-cake makers, etc.)
Heating devices: Electric space heaters, electric heating pads, electric kotatsu (coffee-table type heaters with coverlets), panel heaters, electric mats, etc.)
Others: Ironing presses, hair dryers, vacuum cleaners, futon dryers, etc.)
Household goods Lavatory seats, washlets (a seat-type of bidet incorporating seat warming and warm water irrigator), battery chargers, etc.)
Gas and oil Bathtub boilers, water heaters, floor warmers, fan heaters, space heaters, etc.)
Others Copy machines, automatic vending machines, automobiles, motorboats, marine jets, etc.
Industrial equipment Construction tools, road signs, welding machines, etc.