The role of the expansion valve

As a refrigeration accessory in the refrigeration system, the expansion valve is a new type of throttling device. It is controlled by a microprocessor. Its appearance realizes the direct control and regulation of the refrigeration cycle by the microcomputer. The electronic expansion valve has two structural forms: stepper motor type and solenoid coil type. Strictly speaking, the solenoid coil type is an electromagnetic expansion valve.

Electronic expansion valve usually refers to the stepper motor type. It consists of a valve body, a valve core, a bellows, a transmission mechanism and a pulse stepper motor. The pulse stepper motor is the driving mechanism, and the bellows separates the refrigerant channel from the moving parts to prevent refrigerant leakage. The function of the transmission mechanism is to convert the rotation of the motor into the reciprocating motion of the valve core. There are two types of transmission mechanisms. The reduction transmission mechanism includes a gear pair, a rib pair, a transmission rod, etc. The direct-acting transmission mechanism has no gear pair.

The characteristics of the electronic expansion valve are a large adjustment range, fast and sensitive action, precise adjustment, and stable and reliable. The refrigerant can flow in both positive and reverse directions in the electronic expansion valve, avoiding the disadvantage that the thermal expansion valve has only one direction. When used in a heat pump, the refrigeration system can be greatly simplified. When the refrigeration system is shut down, the electronic expansion valve can be completely closed, eliminating the need to install a solenoid valve at the refrigerant inlet.