The relay is a kind of automatic control device that when the input quantity (electricity, magnetism, sound, light, heat) reaches a certain value, the output quantity will change suddenly. Automotive relays are relays used in automobiles. Such relays have large switching load power, high impact resistance and high vibration resistance. The power supply in automobiles is mostly 12V, and the coil voltage is mostly designed to 12V. Because it is battery-powered and the voltage is unstable; the environmental conditions are harsh, the suction voltage V≤60% VH (rated working voltage); the coil overvoltage is allowed to reach 1.5VH. The power consumption of the coil is large, generally 1.6 ~ 2W, and the temperature rise is high. Environmental requirements are quite harsh: in the engine compartment, the ambient temperature range is -40 ° C to 125 ° C, and the ambient temperature range in other locations is -40 ° C to 85 ° C; the relays used in the engine compartment must be able to withstand sand, dust, water and salt , Oil damage; vibration and shock are quite harsh.
Automotive relays consist of a magnetic circuit system, a contact system, and a recovery mechanism. The magnetic circuit system consists of iron core, yoke, armature, coil and other parts. The contact system consists of static reed, moving reed, contact base and other parts. The restoration mechanism is composed of a restoration spring or a tension spring.
Large size open relay Its size is 35.5 * 25.5 * 21, and the sealed type is open, so it is called a large size open type relay. In addition, it differs in that two antennae are raised at both ends of its upper end surface. It has strong reliability, adapts to high and low temperature, and is more suitable for headlamps, blowers and demisters.
Small power plastic relay The maximum switching power of its contacts is only 150W, and it adopts plastic encapsulation form, which belongs to a low-power plastic encapsulation relay. Although its maximum switching voltage and current are relatively small. It is characterized by strong erosion resistance and low consumption, and is widely used in circuit modules of startup systems.
When a certain voltage or current is applied to the two ends of the electromagnetic relay coil, the magnetic flux generated by the coil passes through the magnetic circuit composed of the iron core, yoke, armature, and working air gap of the magnetic circuit. As a result, the normally closed contact of the contact is opened, and the normally open contact is closed; when the voltage or current across the coil is less than a certain value, when the mechanical reaction force is greater than the electromagnetic attraction force, the armature returns to the initial state, and the normally open contact is opened, The normally closed contact is closed.
Then, the automobile relay can be regarded as an assembly composed of two parts: a control circuit operated by a coil and a main circuit operated by a contact. In the control circuit of the relay, there is only a small working current. This is due to the small contact capacity of the operating switch, which cannot be used to directly control a load with a large amount of electricity. It can only be controlled by the relay’s contacts. On and off.
The relay is both a control switch and a control object (actuator). Take the fuel pump relay as an example, it is the control switch of the fuel pump, but the coil of the fuel pump relay can only form a loop through the ground point of the electronic control unit when the triode is turned on in the electronic control unit.