What Is the Composition, Structure and Working Principle of the Starter?

A starter is also called a motor. Based on the principle of electromagnetic induction, the starter can convert electrical energy into mechanical energy. According to the working principle, the starter can be divided into direct current starter, gasoline starter, compressed air starter, etc. At present, it is widely used. In addition to the tractor parts industry, it is often used in agriculture, such as tractor parts and agricultural machine.

 

 

1. Composition

The starter consists of three parts, DC motor, transmission mechanism and control mechanism.

 

(1) DC Motor

The function of DC motor is to convert the electric energy input by battery into mechanical energy and generate electromagnetic torque.

 

(2) Transmission Mechanism

The transmission mechanism is composed of one-way clutch, driving gear, shift fork, etc. Its function is to mesh the driving gear with the non gear ring when starting the engine, and transfer the torque of the starter to the engine crankshaft. After starting the engine, it can automatically separate the driving gear from the flywheel. In the process of their separation, when the engine flywheel reversely pulls the driving gear, the one-way clutch makes it idle, avoiding the flywheel driving the rotation of the starter shaft.

 

(3) Control Mechanism

The control mechanism mainly refers to the electromagnetic switch of the starter, which is used to connect or disconnect the circuit between the motor and the battery.

 

 

2. Structure of DC Motor

The function of DC motor is to convert the electric energy input by battery into mechanical energy and generate electromagnetic torque. Its structure is composed of armature (rotor), pole, commutator and brush.

 

 

3. Working Principle

(1) Generation of Electromagnetic Torque

It works according to the principle that the current carrying conductor moves under the action of electromagnetic force in the magnetic field. For example, take the simplest two pole DC motor model as an example. According to the left-hand rule, it is determined that both sides of ab and cd are affected by the electromagnetic force F, resulting in the electromagnetic torque M in the counterclockwise rotation direction to make the armature rotate. There are many coils on the actual armature, and the commutator copper sheet has corresponding logarithm.

 

(2) The Principle of DC Motor Torque Automatic Regulation

The armature rotates under the action of the electromagnetic torque M, but the induction electromotive force is generated due to the cutting of the magnetic force line when the winding rotates. According to the right-hand rule, the direction of the armature is opposite to the direction of the armature current ls, so it is called the reverse electromotive force Ef. The reverse electromotive force Ef is proportional to the magnetic flux q of the pole and the rotational speed n of the armature.

Ef= Ceφn

Where Ce is the structural constant of the motor.

Therefore, the voltage balance equation of armature circuit can be deduced. That is, U= Ef IsRs.

Where Rs is the armature loop resistance. It includes armature winding resistance and contact resistance of brush and commutator.

 

When the DC motor is just connected to the DC power supply, the armature speed and the reverse electromotive force Ef are both 0. At this time, the current in the armature winding is the maximum, i.e.lsm==U/Rs, which will produce the maximum electromagnetic torque, i.e. Mmax. If the electromagnetic torque M is greater than the motor resistance torque Mz, the armature will start to accelerate. With the increase of rotational speed n, Ef increases, Is decreases and M decreases. When M drops to be equal to Mz, the armature operates at this speed. If the load of DC motor changes during operation, the following conditions will occur.

 

When the load increases, M<Mz→n↓→Ef↓→IS↑→M↑→M= Mz. It reaches a new stability.

 

When the load is reduced, M> Mz→n↑→Ef↑- >Is↓→M↓→M = Mz. It reaches a new stability.

 

It can be seen that when the load changes, the motor can meet the needs of the load through the automatic changes of speed, current and torque, so that it can work stably under the new speed. Therefore, DC motor has the function of automatically adjusting torque.

 

Since the starter is one of the common tractor parts, agricultural machine and John Deere parts, people need to know more about it.