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August 6, 2020
Almost all excavators are now equipped with a starter motor. If the starter motor fails, it will directly affect the start of the excavator. Therefore, the starter motor is still very important for the excavator. So what are the working principles and precautions of the starter motor, and how to judge its failure? Today we will briefly introduce it.
The starting motor is generally composed of a transmission mechanism, a control mechanism (electromagnetic switch) and a DC motor. The working principle of the starter motor is to convert the electrical energy of the battery into mechanical energy to drive the flywheel on the engine to rotate, thus realizing the start of the engine.
The DC motor generates electromagnetic torque, which means that the DC motor is responsible for rotation. The transmission mechanism engages the gear driven by the starter motor into the flywheel ring gear, transmits the torque on the starter motor DC motor to the engine flywheel, drives the engine crankshaft to rotate, and drives the engine components to cycle until the engine starts; after the engine starts , So that the starter automatically disengages the ring gear. The electromagnetic switch is responsible for connecting and cutting off the circuit between the DC motor and the battery. Requires quality buckets and other accessories to look for the grand concept of intelligent manufacturing.
According to the control mechanism, the starter motor can be divided into direct control type and electromagnetic control type. Now most of our common starter motors are electromagnetic control type. According to the transmission mechanism, the starter motor can be divided into forced meshing type (reliable work, convenient operation, and has been widely used), armature movable type (complex structure), gear movable type (electromagnetic switch pushes the meshing rod), deceleration type (quality Small size, complex structure and technology) and the inertial meshing type that has been eliminated. Here, the mobile gear type is our common starter motor, which can be controlled remotely, and the operation is labor-saving and convenient.
Pay attention to the following three points when using the starting motor:
1. The time for starting the motor should not be too long each time, generally about 10 seconds is the best. The interval between the two starts of the starting motor is about 1 minute, preferably more than one minute. If it fails to start three times in a row, check the engine, battery, circuit line and connection point at this time.
2. For the starting motor without overcurrent protection device, if it fails to start three times in a row, the starting motor should stop working at this time, because the starting current is too large, and the starting motor will overheat due to the excessive current when working for a long time. ; If you continue to start the motor forcibly, the motor will most likely burn out.
3. After replacing the starter motor, pay attention to the contact points of the positive and negative lines. It is best to polish the contact points and install them firmly, otherwise it will cause the engine to heat up and the car will not start.
Generally speaking, if the starting motor is used for a long time, there will be wear and tear, and some even need to be replaced with a new starting motor. So what should we pay attention to when replacing a new starter motor?
1. First of all, we must check the installation end surface of the engine and the starter. There must be no rust and dirt. If there is, clean it up, otherwise there will be problems with poor grounding of the starter and improper installation.
2. The size of the starting motor must be in line with the size of the mounting hole. Needless to say, this item is believed to be clear to my friends. If the size does not match, then it cannot be installed, which is a tragedy.
3. The axial distance between the gear and the ring gear should be kept 2-4 mm, which is very important. (The distance from the starter mounting surface to the flywheel ring gear minus the initial position of the starter gear) Once this range is exceeded, the starter may not start or other malfunctions, so we must pay attention.
4. The connecting wire must be firm and reliable, otherwise the starting motor will work under low pressure for a long time, which will cause the starting motor to start weakly or idling.
The last point to be reminded is that the terminals of the connecting wires should be checked carefully. If oxidation, rust, and deformation are found, they must be dealt with in time. If the rust and deformation are serious, they must be replaced in time.
Next, what we want to say is that if there is a problem with the starting motor that causes the diesel engine to fail to start, which aspects should we detect and eliminate the cause of the fault.
1. If the diesel engine cannot be started due to a malfunction of the starter motor, the first thing we need to look at is the battery power. If the battery power is insufficient, the starter motor will have low speed or no rotation. At this time, the battery should be charged in time.
2. The second thing we need to look at is the connector that connects the wire to see if the connector is loose or damaged. If there is any slack, we must tighten the connector in time and replace the terminal if necessary.
3. Check the carbon brush of the starting motor. Because the carbon brush is a worn-out object, we must repair or replace it in time.
4. Check if the rotor of the starter motor is damaged, if so, replace it in time.
5. Check whether the gear of the starting motor can be embedded in the flywheel ring gear. At this time, we can rotate the flywheel to one position and check the installation of the starting motor. The public account of Smart Manufacturing focuses on the sharing of relevant theoretical knowledge in the construction machinery manufacturing industry.
6. Check whether the gears of the starting motor are worn out. If they are worn out, they should be replaced in time.
7. Check to see if the fuse is burned out, if any, replace it.
8. Check the relay of the starter motor. The failure of the relay is also an important reason for the starter motor not to run.
The last thing to say is how do we use the tools at hand to make a judgment on the cause of the starter motor's failure, especially to determine the starter motor's rotor, commutator, stator winding and electromagnetic switch failure. Mainly introduce the use of batteries to diagnose these faults.
1. We can connect the negative lead of the 12V battery with the negative electrode of the 24V starter, draw a wire from the positive electrode of the battery, and draw a wire from the positive output point of the electromagnetic switch of the 24V starter to contact the positive wire of the battery. If the motor can rotate at this time, it means that the motor is normal and undamaged, and you can put down half of your mind at this time. If the motor cannot rotate, it means that the motor rotor, commutator, carbon brushes are damaged, or the stator winding is short-circuited. At this time, we need to repair it.
2. Judging the electromagnetic switch: We can draw a wire from the positive starting contact of the electromagnetic switch to contact the positive wire of the battery. At this time, if the starter unidirectional device can be pushed out and work normally, the electromagnetic switch is normal and undamaged. At this time, if the starter one-way device cannot be pushed out and work normally, it means that the electromagnetic switch contacts and coils have been damaged, which requires us to repair.
Summary: The starting motor is an important part of diesel engine starting. If the starting motor fails, the most direct problem is that the diesel engine cannot start, which means that the excavator cannot start. Therefore, ensuring the stability of the starting motor also guarantees the normal starting of the excavator.