The engine transitions from a static state to a working state, and the crankshaft of the engine must be rotated by external force, so that the flammable mixture is sucked in the cylinder and the combustion is expanded, and the duty cycle can be carried out automatically. The whole process of the crankshaft starting to rotate under the action of external forces until the engine begins to idle automatically is called the start of the engine.
The role of the starting system is to drive the engine flywheel to rotate, so that the engine crankshaft reaches the required starting speed, so that the engine enters a state of self-operation. When the engine enters the normal operation state, the start system ends the task and stops working.
The starting system is composed of a battery, a starter, a starting relay, an ignition switch, etc., as shown in the following figure▼ ▼
The starter is the core component of the starting system, its role is to convert the electrical energy of the battery into mechanical energy, and then start the engine through the transmission mechanism.
The starter is composed of three parts: DC motor, transmission mechanism and electromagnetic switch, as shown in the following figure ▼
The starter is not uniformly specified in the circuit diagram, and the common symbols are shown in the figure below ▼
◆◆ Direct current motor
◆◆
The role of the DC motor is to convert the electrical energy input from the battery into mechanical energy, generating electromagnetic torque.
DC series excitation motor is composed of armature (rotor), magnetic pole (stator), brush and brush frame, chassis, etc., and the decomposition diagram is as follows ▼
◆◆ Transmission mechanism
The role of the transmission mechanism is to make the starter drive gear mesh with the ring gear of the engine flywheel when starting the engine, and transmit the torque of the motor to the engine crankshaft; after the engine starts, it can cut off the power transmission between the crankshaft and the motor in time.
The transmission mechanism is composed of drive gears, one-way clutches, forks, etc. The working diagram of the transmission mechanism is as follows ▼
When the engine starts, the ignition switch is placed in the starting gear, the coil in the electromagnetic switch is energized to generate electromagnetic force to suck the iron core in, so the fork is driven to rotate, and the one-way clutch is launched by the fork head, so that the drive gear meshes into the flywheel ring gear, and the armature shaft begins to drive the engine crankshaft to rotate.
After the engine starts, as long as the ignition switch is released, the coil in the electromagnetic switch is powered off, the electromagnetic force disappears, the iron core exits, the fork returns, the fork head dials back the one-way clutch under the sliding condition, and the drive gear and the flywheel ring are separated from the mesh.
◆◆ Magnet on/off
Electromagnetic switch is also called control mechanism, the role of the electromagnetic switch is to turn on or cut off the circuit between the DC motor and the battery, and control the meshing and separation of the gear ring of the starter drive gear and the engine flywheel.
The electromagnetic switch is mainly composed of suction and pull coil, holding coil, iron core, contact plate, etc., as shown in the following figure ▼ ▼
The direct control type electromagnetic switch control circuit is shown in the following figure ▼
When starting, the ignition switch is hit to the st block, the electromagnetic switch is energized, and its circuit is ▼
Battery positive → ignition switch→ 50 binding posts→ suction and pull coil→c binding posts→ starter excitation windings→ armature → iron → battery negative. At the same time, the current is also passed through the coil; the circuit is the positive → ignition switch of the battery→ 50 binding posts→ the coil is → the iron → the battery negative.
At this time, the magnetic field core moves to the left, driving the fork to push the starter drive gear to the right, meshing with the flywheel ring gear. When the drive gear engages with the flywheel, the contact disc connects the 30 binding posts on the electromagnetic switch with the c binding post, so the main circuit of the starter is connected, and the circuit is ▼
Battery positive → 30 binding posts → contact disc →c terminal posts → starter excitation windings → armature → iron → battery anode. The DC motor generates a powerful torque through a unidirectional clutch to drive the flywheel to rotate and start the engine.
After the starter is activated, the ignition switch is released, the ignition switch returns from the st stop to the on block, the 50 terminal post is powered off, but the suction and pull coil and the holding coil inside the electromagnetic switch get the current through the main switch that is still closed, and its current loop is ▼
Battery positive → 30 binding posts→ contact disc → suction coil→ keep the coil → tie iron → battery negative
At this time, the suction and pull coil and the direction of the current that keeps the coil through are opposite, the direction of the generated magnetic field is also opposite, the electromagnetic suction force cancels each other out, the magnetic field core is rapidly returned under the action of the return spring due to the loss of magnetic field force, the contact plate is separated from the c binding post and the 30 binding post, and the driving gear and the flywheel are disengaged from the mesh, and the starter stops working and starts to complete.
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