Learn what central door lock is in one article

What is a central door lock?

The central door lock is designed to make the car easier and safer to use, and to centrally control the locking and opening of the four doors. In layman's terms, there is a button on your driver's door. After pressing it, the door locks and glass of the other three doors cannot be controlled individually, and you have to control it alone on the door next to you. Conversely, you can control it alone. The working principle of the central door lock is to convert electrical energy into mechanical energy, and use the motor to drive the gear to rotate to open and close the car door.

Basic structure

There are still many types of central locks installed in cars. All of them are basically composed of door lock switches, door lock actuators and door lock controllers.

Door lock switch: The central control switch is composed of a main switch and a sub-switch, which accounts for the vast majority of the central control switches. The main switch is installed on the door next to the driver, and the driver can lock or open all the doors of the car by operating the main switch; the sub-switches are installed on other doors and can control a door separately.

Door lock actuator: The door lock actuator is controlled by the door lock controller and follows the driver's instructions to lock or open the door. There are three main types of door lock actuators: electromagnetic, DC motor and permanent magnet motor. Their structures all perform door locking or door opening actions by changing the polarity and switching the direction of movement.

(1) Electromagnetic type: It contains two coils, which are used to open and lock the door lock and perform the centralized tasks of the door lock. The button is usually in the middle position. When the lock coil is passed through a positive current, the armature drives the rod to move left and the door is locked; when the open coil is passed through a reverse current, the armature drives the connecting rod to move right and the door is opened.

(2) DC motor type: It transmits power to the door lock through the transmission device (the transmission device includes screw transmission, rack transmission and spur gear transmission) to open or lock the door lock. Since the DC motor can rotate in both directions, the door lock can be locked or opened by the forward and reverse rotation of the motor. Compared with the electromagnetic actuator, this actuator consumes less power.

(3) Permanent magnet motor type: Permanent magnet motor mostly refers to permanent magnet stepper motor. Its function is basically the same as the first two types, but the structure is quite different. The rotor has convex teeth, and the radial gap between the convex teeth and the stator magnetic poles is small and the magnetic flux is large. The stator has multiple electromagnetic poles evenly distributed in the axial direction, and each electromagnetic coil is arranged radially. The stator is surrounded by an iron core, and each iron core is wound with a coil. When the current passes through the coil of a certain phase, the iron core of the coil generates suction to attract the convex teeth on the rotor to align with the magnetic poles of the stator coil. The rotor will rotate to the minimum magnetic flux, which is a step position. To make the rotor continue to rotate a step angle, a pulse current is input to the stator coil of the next phase according to the required rotation direction, and the rotor can rotate. When the rotor rotates, the door lock is locked or opened through the connection.

Door lock controller: It is a control device that provides locking or opening pulse current for the door lock actuator. It has the function of controlling the direction of the current flowing through the actuator. At the same time, it has a timing function to shorten the working time. Regardless of the type of door lock actuator, it controls the left and right movement of the connecting rod by changing the direction of the current flowing through the actuator to achieve the locking and opening of the door lock.

There are many types of door lock controllers, which can be roughly divided into three types according to their control principles: transistor type, capacitor type and car belt induction type.

(1) Transistor type: The transistor door lock controller has two relays inside, one for closing the door and the other for opening the door. The relay is controlled by a transistor switch circuit, which uses the charging and discharging process of the capacitor to control a certain pulse current duration, so that the actuator can complete the door locking and opening actions.

(2) Capacitive type: This door lock controller uses the charging and discharging characteristics of the capacitor. The capacitor is normally fully charged. When working, it is connected to the control circuit to discharge the capacitor, which powers the relay and causes it to close for a short time. After the capacitor is completely discharged, the current passing through the relay is interrupted, causing its contacts to disconnect, and the door lock system is no longer working.

(3) Vehicle speed sensing type. It is equipped with a 10km/h sensing switch. When the vehicle speed is greater than 10km/h, if the door is not locked, the driver does not need to do anything, and the door lock controller will automatically lock the door.

Working principle of car central locking

Working principle of automobile central lock The central lock is mainly composed of two switches S1 and S2, door lock relay, 5 bidirectional DC motors and fuses. The switch of the lock is controlled by the line control relay. When the left front door switch is turned on, the circuit is connected, the normally closed contact of the relay is grounded, and the motor starts to work to open the door lock and the rear door luggage lock. When the switch is locked, the relay is connected, the normally closed contact opens, and the motor is connected at the same time. The motor starts, and the door lock and the rear door luggage lock are closed. According to its structure, the central lock can be divided into two types: bidirectional air pressure pump type and micro DC motor type; according to its control method, it can be divided into two types: with anti-theft system and without anti-theft system. Like the DC motor type, it mainly controls the opening and closing of the door lock by controlling the circuit current to control the motor. It is mainly composed of switches, motors, transmission and execution parts and related relays.

The wireless remote control function of the central lock means that the door can be opened and locked from a distance without inserting the key into the keyhole. Its biggest advantage is that it can be unlocked (opened the door) and locked (locked the door) from a distance and conveniently at any time of day or night without finding the keyhole.

The basic principle of remote control is: weak radio waves are sent from the car owner, the car antenna receives the radio wave signal, the electronic controller ECU recognizes the signal code, and then the actuator (motor or electromagnetic manager coil) of the system performs the opening/closing action. The system mainly consists of two parts: the transmitter and the receiver.