1. Composition and principle of automobile starting system

Automobile starting system is composed of battery, starting switch, starting relay, starting motor, etc., whose function is to convert the electric energy of the battery into mechanical energy through the starting motor to start the engine operation.The main role of the starter is to convert the electrical energy of the battery into mechanical energy, generate electromagnetic torque, and the torque to the engine flywheel, drive the engine start operation.The starting switch is used to switch on the starter's electromagnetic switch circuit to make the electromagnetic switch work.The starting switch of the gasoline engine is combined with the ignition switch, that is, the ignition switch is provided with the starting gear.The starting relay is used to protect the starting switch from ablating due to large current passing directly through the starting switch.When the ignition switch is connected to the starting gear, the starting relay coil circuit is connected, and the circuit is:

Battery positive ignition switch "ST" stop starting relay

"Ignition switch" connecting column coil with iron battery negative electrode;The two coils generate magnetic field in the same direction, magnetize the iron core, and move the active iron core forward. The front of the iron core drives the contact plate to move the two switches. The back end drives the shifting fork through the earring, making the driving gear and flywheel mesh.After the contact plate connects the two switch terminals of the motor, the motor circuit is connected.This circuit resistance is very small, the current can reach hundreds of amperes, the motor produces a large torque, driving the flywheel rotation.When the motor is switched on, the suction coil and the additional resistance are short-circuited.Start switch disconnects, start relay stops working, contacts open.The motor switch is disconnected and the drive gear and flywheel are separated.

2. Common fault diagnosis of starting system

Common failures of the starting system include: the starting switch is switched on, and the starter does not turn, idles or runs weakly.

2.1 the starter does not turn

The phenomenon is that when the ignition switch turns to the starting gear, the starter does not turn.

2.1.1 cause analysis

(1) power failure.Battery loss or internal damage, battery wire and battery terminal bad contact, battery wire and starter terminal loose connection, battery wire bad contact or loose connection, battery wire broken.

(2) control the fault of the line part.Ignition switch or starting relay (or composite relay) fault, electromagnetic switch "fire terminal" ignition switch starting relay

(3) starter failure.The electromagnetic switch contacts are abraded, the electromagnetic switch coil is broken, short circuit, cast iron, the pivot is bent or the bearing is too tight, the commutator is dirty or burnt out, the brush is worn too short, the spring is too soft, the brush is stuck in the frame and cannot contact the commutator, the armature winding or excitation winding is broken, short circuit, cast iron.

2.1.2 diagnosis and exclusion

(1) check whether the storage battery is sufficient and the power supply line is trouble-free.Use the battery high rate discharge meter, check the battery technical status, check the power supply wire contact, can also be used to turn on the headlight or honk, check the light brightness and sound intensity of the method, to check whether there is a fault in the power line.

(2) determine whether the fault is in the starter or in the control line.If the "fire terminal" and "start terminal" on the short connection electromagnetic switch occur as follows: first, the starter is running, indicating that the starter is in good condition and the fault is in the control line.The short-connection method can be used to check whether the starting switch, the relay and the conductor are normal or not. The fault location can also be determined by checking the voltage of the conductor.

Second, the starter does not turn, indicating the fault in the starter.Then short-connect the "wire terminal" and "stator winding terminal" on the electromagnetic switch. If the starter runs normally, the electromagnetic switch has a fault.If it still does not turn, it indicates that there is something wrong with the dc motor of the starter.

2.2 weak rotation of starter

Its phenomenon is to turn on the starting switch, the starter rotation slow or not continuous operation.

2.2.1 cause analysis

(1) power failure.Battery storage is insufficient, power supply wire joint loose, dirty, poor contact.

(2) failure of starter part.The ablative contact of the electromagnetic switch contacts and contact plates is poor, and the electromagnetic switch coil is local short circuit;The surface of the commutator is ablative and dirty;Brush wear too much, the spring is too soft, make brush and commutator contact bad;The armature winding or the magnetic field winding local short circuit, causes the starter power to decline;The electric pivot is bent, the bearing clearance is too big, causes the rotor and the stator to collide;The starter bearing is too tight and the rotational resistance is too large.

2.2.2 diagnosis and exclusion

(1) check whether the storage battery is sufficient;Check whether the battery pole column, wire and wire joints are in good contact.

(2) if the battery and power supply wires are in good condition, the fault is in the starter part.Disassemble and check the starter to troubleshoot.

2.3 idle starter

Its phenomenon is: turn on the ignition switch starting gear, the starter is only high speed idling, can not drive the engine to run.

2.3.1 cause analysis

One way clutch slip or damage;Shifting fork deformation or loosening fork linkage;Improper travel adjustment between driving gear of starter and gear ring of flywheel, or the driving gear cannot move freely;Electromagnetic switch core travel is too short;The starter drive gear or engine gear ring is badly worn or damaged.

2.3.2 diagnosis and exclusion

(1) when the starter is idling, the speed is very high, although the drive gear has engaged with the gear ring, but can not drive the flywheel rotation, can hear the "buzzing" sound of high-speed rotation, no contact sound, generally one-way clutch slip or damage.

(2) when the starter is idling, if there is a serious sound of rubbing the gear teeth, it indicates that the flywheel gear or the driving gear of the starter is seriously worn, the starter should be removed for further inspection, and the driving gear or gear ring of the flywheel should be replaced according to the actual situation.

(3) if there is a light friction sound when the starter is idling, that is, the driving gear is not engaged with the gear ring of the flywheel, the electromagnetic switch will be connected in advance, indicating that the iron core travel is too short, the starter should be removed to adjust the time when the starter is connected.

(4) if there is a crash sound when starting, check whether the connecting mechanism of the shifting fork is loose and whether the fixing bolt of the starter is loose.

3. Inspection method of main parts of starting system

After the initial determination of the fault point or fault range, the relevant parts can be checked to identify the faulty parts.

3.1 starting relay inspection

The diode file of the digital multimeter can be used to check whether the coil is broken.The ohms are used to detect the resistance between the corresponding terminals of the relay coil to determine whether there is a short circuit.For the inspection of relay contacts, a certain voltage can be applied between the corresponding terminals of relay coil and the opening and closing conditions of relay contacts can be observed to judge whether the relay is normal.

3.2 electromagnetic switch inspection

Check the pull coil or hold coil in the electromagnetic switch by using the resistance of the multimeter.Connect the multimeter between the terminal post of the electromagnetic switching power supply and the terminal post of the starter power supply.Connect the multimeter between the junction post of the electromagnetic switching power supply and the switch body.If there is no problem with the coil, the electromagnetic switch can only be removed.For the repaired electromagnetic switch, the traction performance, retention performance, reset performance should also be tested after assembly.

3.3 one-way clutch inspection

Use the hand along the forward and reverse rotation drive gear, if can not turn, indicating that the one-way clutch bite dead;If both can turn, indicating one-way clutch failure.If no fault is found through the above inspection, the one-way clutch can be removed and clamped on the vise, a spline shaft can be inserted into the spline sleeve, the torque wrench is connected to the spline shaft with the sleeve, and the torque wrench can be turned counterclockwise, the one-way clutch should be able to withstand the specified value within 1.2 times of the torque without slipping.Otherwise, indicating one-way clutch failure.

3.4 inspection of starter motor

The battery terminal post on the short connection electromagnetic switch and the power terminal post of the starting motor can be used. If the starting motor does not work normally, the internal fault of the starting motor can be considered.Usually, the motor has the phenomenon of uneven rotation at the moment when it is energized. The main reason may be the bad contact between the brush and the commutator surface, or the broken circuit in the armature winding.If the motor runs normally when idling, but cannot drive the engine to rotate, the reason may be a short circuit in the armature winding, or it may be a bad lap iron brush.If the contact spark of the external circuit is very big, it may be that the magnetic field winding or brush frame has a lap iron fault.