What is a relay and what does it do? In fact, the function of automobile relay is the same as that of general relay. In the electrical automation industry, relay plays the role of "switch", that is, it controls the on-off of one circuit to control the on-off of the next circuit. Vehicle relays are generally electromagnetic or solid. To put it bluntly, electromagnetic relay means that the coil is energized to generate a magnetic field to attract the moving electric shock and attach it to the static contact to connect the circuit. However, most of the current used by solid-state relays generates electrons through diodes, and the electrons collide with an object similar to a triode. When the photoelectric intensity reaches a certain value, the triode is turned on and the next circuit is connected.
1) According to the purpose, it can be divided into two types: functional relay and control relay. For example, flash relay and wiper relay belong to functional relay, while ordinary relays that only start the circuit on and off and switch belong to control relay.
2) According to the contact state, it can be divided into three types: normally open type, normally closed type and mixed type.
3) According to the control mode, it is divided into current type and voltage type: current type relay is a relay that operates according to a certain current value; It and other components form a practical circuit, such as the flash relay on the car. The greater the current, the higher the flash frequency. Voltage relay is a relay that operates according to a certain voltage value, that is, when the voltage of the controlled circuit is greater than or less than a certain value, the relay will connect or disconnect the controlled circuit. Such as light relay, horn relay, etc. Voltage relay is mainly used to control large current consuming circuits. Generally, the coil control voltage of this relay is greater than 7V to work, and it stops working when it is less than 5V.
4) According to the connection mode, it can be divided into post type and plug type.
5) According to the protection mode, it can be divided into resistance protection type and diode protection type, and the function of control relay is to control large current with small current.
When a certain voltage or current is applied to both ends of the coil of the electromagnetic relay, the magnetic flux generated by the coil passes through the magnetic circuit composed of the iron core, yoke, armature and the working air gap of the magnetic circuit, and under the action of the magnetic field, the armature is attracted to the pole surface of the iron core, thus pushing the normally closed contact to be disconnected and the normally open contact to be closed; When the voltage or current at both ends of the coil is less than a certain value and the mechanical reaction is greater than the electromagnetic attraction, the armature returns to the initial state, and the normally open contact is disconnected and the normally closed contact is connected.
Then, the automobile relay can be regarded as a collection of two parts: the control circuit with coil working and the main circuit with contact working. In the control circuit of relay, there is only a small working current, because the contact capacity of the operating switch is small, which can not be used to directly control the load with large electricity consumption, and it can only be controlled by the contact of relay.
Relay is not only a control switch, but also 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 grounding point of the electronic control unit when it drives the triode to conduct.
If the installation direction is consistent with the impact-resistant direction of the relay, the performance of the relay can be fully exerted. It is suggested that the shock direction is perpendicular to the movement direction of the contact and armature, which can effectively improve the vibration and impact resistance of the normally closed contact in the non-excited state. When installing, make the contact axis of the relay parallel to the ground, which can avoid contact spatter and charring falling on the contact surface and improve contact reliability. Multi-group relays should avoid the small load contact under the large load contact.
When installing multiple relays at close range, it will lead to abnormal heating, which is generally recommended to be 2mm apart.