The starter motor is mainly composed of three parts: a DC motor, a transmission mechanism, and an electromagnetic switch. Its working principle is as follows:
Working principle of DC motor
The DC motor is the core component of the starter motor, which operates according to the laws of electromagnetic induction and Ampere's law. When current passes through the armature coil of a motor, the energized conductor is subjected to force in the magnetic field, resulting in rotational motion. Due to the small torque and unstable speed generated by a single coil, in actual motors, numerous coils are wound around the armature, resulting in an increase in the number of commutator segments. These multiple sets of coils work together in the magnetic field to ensure that the motor can generate sufficient torque and stable speed, providing a stable and strong power foundation for the starter motor to drive the subsequent transmission mechanism and drive the engine to operate.
Working principle of transmission mechanism
The transmission mechanism plays a crucial role in the working process of the starter motor, and its main task is to accurately transmit the rotational motion of the DC motor to the flywheel of the engine. At the moment of start-up, the transmission mechanism will smoothly move the driving gear outward along the keyway of the starter shaft under the action of electromagnetic force or other driving methods, until it tightly meshes with the flywheel ring gear of the engine. At this point, the torque generated by the motor can be smoothly transmitted to the engine crankshaft through the flywheel, providing the initial rotational power for the engine to start. After the engine is successfully started, the speed of the flywheel will rapidly increase. Due to the meshing relationship between the flywheel and the driving gear, it will in turn drive the motor shaft to rotate at high speed through the driving gear. In this case, if not controlled, the motor will run at an overspeed, which may cause serious damage. Therefore, the transmission mechanism has overspeed protection function. When the engine speed exceeds a certain threshold, it will promptly disconnect the drive gear from the motor, effectively preventing motor overspeed and ensuring the safety and stability of the entire starter system.
Working principle of electromagnetic switch
The electromagnetic switch is like the "control center" of the starter motor, responsible for accurately controlling the on/off of the starter motor circuit. When the driver presses the start button inside the cab, current flows into the attraction coil and holding coil of the electromagnetic switch, which quickly generate strong electromagnetic attraction when powered on. Under the action of electromagnetic attraction, the movable iron core begins to move. On the one hand, the movable iron core will pull the transmission meshing mechanism, causing the starter small gear to move forward along a specific track and ultimately precisely mesh with the engine flywheel ring gear, preparing for power transmission; On the other hand, as the movable iron core moves further, it will push the switch contacts to connect, thereby energizing the DC motor to start running, converting electrical energy into mechanical energy, driving the engine crankshaft to rotate, and achieving the starting process of the engine. Once the engine is successfully started and begins to operate autonomously, the electromagnetic switch will automatically disconnect the circuit according to the preset control logic, stop supplying power to the DC motor, and stop the starter motor from working, avoiding unnecessary energy consumption and component wear, ensuring the efficiency and reliability of the entire starting process.
