What is the working principle of the original 4-wire central control motor?
2 Answers
The original 4-wire central control motor operates based on the principle of electromagnetic induction. A current-carrying conductor moves under the force exerted in a magnetic field. The energized coil rotates under the force in the magnetic field, driving the starter rotor to rotate, and the small gear on the rotor drives the engine flywheel to rotate. The starting system converts the electrical energy stored in the battery into mechanical energy. To achieve this conversion, a starter must be used. The function of the starter is to generate power through a DC motor, which drives the engine crankshaft to rotate via the transmission mechanism, thereby starting the engine. The starting system includes the following components: battery, ignition switch (starter switch), starter assembly, starter relay, etc. Although the starters used in different types of vehicles vary in form, their DC motor parts are basically similar, with the main differences lying in the transmission mechanism and control device. The function of the DC series-wound motor is to convert the electrical energy input from the battery into mechanical energy, generating electromagnetic torque. The transmission mechanism, also known as the starter clutch or engagement device, functions to engage the small gear on the starter shaft with the flywheel ring gear during engine starting, transmitting the starter's torque to the engine crankshaft. After the engine starts, it automatically disengages the starter small gear from the flywheel ring gear.
I've taken apart several car door central locking mechanisms before, and the working principle of this 4-wire motor is quite interesting. Inside the motor is actually a DC motor responsible for driving the lock rod up and down. Those four wires are divided into two groups: one group controls the locking action, and the other controls the unlocking action. For example, the brown and black wires are used to drive the motor forward for locking, while the blue and white wires are responsible for reversing to unlock. When 12V power is applied, the motor reverses based on the direction of the current. The other two wires are for position feedback—when the lock rod reaches the top, an internal contact switch closes, sending a signal back to the car's computer to display the door lock status. Without these feedback wires, the car wouldn't know whether the lock is properly engaged, and even the dashboard lock indicator might malfunction. The most common issue is oxidation in the connectors causing poor contact, which can usually be fixed by removing the door panel and cleaning the connectors.
