Diesel generator maintenance training diesel engine -p25-p28 diesel generator crank ...

Diesel generator maintenance training diesel article -p25-p28 diesel generator crank linkage mechanism

Section 2 Diesel Engine Crank Linkage Mechanism

The diesel engine crank connecting rod mechanism is composed of a piston connecting rod assembly and a crankshaft flywheel assembly, etc. It is a mechanism for ensuring that the diesel engine normally performs a working cycle and completes energy conversion. In this mechanism, the thermal energy generated by the combustion of diesel is converted into mechanical energy, and the reciprocating motion of the piston is converted into a rotational motion of the crankshaft, thereby outputting power. The working conditions of the crank connecting rod mechanism are the worst, and the clearance between the components requires a high clearance. The maintenance personnel must disassemble and assemble according to the technical requirements to reduce the failure rate of the mechanism.

First, the piston rod assembly

The piston rod assembly is an important component of the diesel engine combustion chamber. It is mainly composed of a piston ring, a piston pin, a piston standard, a connecting rod bushing (not shown in the figure), a connecting rod and a connecting rod screw.

The shape of the piston rod assembly is shown in Figure 2-22.

1. Defective piston failure and maintenance methods

The piston is generally cast from an aluminum alloy and its construction can be divided into tops, as shown in Figure 2-23. The head and cylinder head and cylinder sleeve of the piston compose the combustion chamber and are designed.

The three parts of the ring groove and the skirt, as shown in Figure 2-23, are designed for mounting the piston ring.

In the process of use, the piston is easy to wear the ring groove, followed by the skirt and the pin hole. The main reason for wear of piston ring paddles is the high temperature and pressure of the combustion chamber. The piston generally has several grooves, but the ring that is most susceptible to wear is the combustion chamber. When the piston ring groove is worn out, more high-temperature and high-pressure gas will enter the crankcase, and more oil will enter the combustion chamber at the same time.

After the piston is damaged, it can be checked by observation and judgment. When the diesel engine exhaust pipe emits blue smoke or power drops, the majority of faults occur in the ring groove or piston ring; when the diesel engine is at idle, the sound of air leakage in the crankcase can be heard. The repair of the piston is more difficult, and when the piston wear effect is serious, the same type of new piston is generally replaced.

2. Piston ring easy to produce the array and repair methods

Piston rings are divided into gas rings and oil rings, as shown in Figure 2-24. The role of the gas ring is to prevent the high temperature and high pressure gas in the combustion chamber from entering the crankshaft foil. The role of the oil ring is to ensure that the oil distribution on the inner wall of the cylinder liner is uniform and to prevent the oil from entering the combustion chamber.

The diesel generator piston rings are prone to serious wear, weak elasticity, internal squeezing and breakage during long-term use. The piston rings are subjected to high temperature, high pressure and reciprocating motion during long-term use, resulting in increased wear. When the wear reaches a certain limit, the elasticity of the piston ring begins to decrease, and the end play, backlash, and backlash also gradually increase, thereby weakening the sealing effect on the combustion air. When the sealing effect is weakened, the phenomenon of incomplete combustion will occur after the diesel fuel is injected into the combustion chamber. The high temperature and high pressure gas generated in the combustion chamber will also enter the crankcase through the piston ring, which will increase the carbon deposition in the piston ring and weaken the sealing effect. Can cause oil to lick.

The longer it is used, the more internal piston rings will condense. Piston ring breakage is generally caused by incorrect assembly methods or by the stuck piston ring.

After the piston ring is damaged, it can be checked by observation and judgment. When the exhaust pipe of a diesel engine emits black smoke, diesel oil enters into the diesel engine, and the power drops rapidly, the piston ring may generally be regarded as having a failure. The piston ring is a consumable part and the price is relatively cheap. After the damage, the piston ring of the same level as the cylinder and the piston can be replaced.

3. Link-prone failures and maintenance methods

The main role of the diesel generator connecting rod is to connect the piston and the crankshaft and transmit the force of the gas from the piston to the crankshaft so that the crankshaft outputs power. In order to make the connecting rod not deform under the strong alternating load, the connecting rod is usually made of high-quality carbon steel or steel. The connecting rod consists of a small head, a shaft, and a large head, as shown in Figure 2-25.

The connecting rod is prone to bending, twisting, and bending during long-term use.

Double bending, fracture, and large and small head wear and other faults. even

The main reasons for the damage of the rods are as follows: First, they are used in an overloaded manner. Second, they are not assembled according to the torques and fit clearances specified in the technical specifications. For example, the torsion moments of the connecting rod bolts are too small or too large, and the assembly of the bearing bushes is incorrect. The connecting rod is damaged. Thirdly, the associated failure, such as the valve falling into the cylinder and the occurrence of a cylinder accident in the diesel engine, will cause the connecting rod to bend or break.

It is recommended that repair shops without conditions should replace the same type of new connecting rod when they encounter bent, twisted, double bent or broken links. The repair shop with practical experience and special tools can continue to use the connecting rod after correction.

4. Faults and Maintenance Methods of Connecting Rod Village Sets

The role of the diesel generating set link bushing is to reduce the rotational wear of the piston pin. In order to reduce the wear in the small hole of the connecting rod, the bushing is generally pressed in the small head hole. The bushing is mostly made of bronze or aluminum alloy. In order to ensure that the inside of the bronze or aluminum alloy bushing is fully lubricated, oil holes are generally drilled at the top of the connecting rod head or inside the Jixian County, and the inner wall of the bush is lubricated by splash or pressure. Figure 2-26 shows the appearance of the connecting rod bushing.

The most common failure of the connecting rod liner is excessive wear. * When the connecting rod liner is excessively worn, the gap between the liner and the piston pin will increase, causing the diesel engine to make an abnormal noise. The reasons for the failure of the connecting rod bushing are as follows: First, normal wear; Second, the diesel engine is overloaded and the bushing is overloaded; Third, the bushing oil passage is blocked.

The test method after the failure of the connecting rod bushing is shown in Figure 2.27. After the diesel engine starts, if the sound of the piston pin is noticeably weakened or disappeared after a certain high-pressure fuel pipe is disconnected, the sound of the connecting rod bushing of the cylinder may be seriously worn out after the high-pressure fuel pipe is turned on.

The link lining will belong to the wearing parts and will be replaced by qJ after replacement.

5. Convenient internal faults in the connecting rod and repair methods

The physical appearance of the connecting rod bulkhead is shown in Figure 2-25. The part of the connecting rod that can be disassembled is called the big head bearing cap. When assembling through Lianpian bolts, connecting rods (or bushes) are installed on the inner walls of the bearing caps and connecting rods to reduce the wear of the crankshaft neck and the inner wall of the connecting rod.

In the long-term use, the connecting rod is the most vulnerable part of the connecting rod, as shown in Figure 2-28. The failures of the connecting rods are scratches, scratches, uneven wear, cracks and flaking of alloy layers, severe wear, and burning of tiles.

The main reasons for the internal failure of the connecting rod are: First, improper use of maintenance, such as more oil impurities, diesel engine overload operation, too little oil, the diesel engine does not preheat and instantaneously raise the speed too high, oil pressure Lower, etc.: — is improperly assembled or has manufacturing defects.

Inspection methods for damage to the connecting rod bulk are:

1After the diesel engine is started and warmed up by the repairer, it suddenly accelerates. If suddenly there is an obvious “dang and when” sound at the side cover of the machine, and then it suddenly falls from high speed to idle speed, the above sounds weaken or disappear, and it can be concluded. There is a problem with the inside of the connecting rod.

2 Use the cylinder-by-cylinder blocking method to conduct tests. If the “dang/dang” sound of a certain cylinder is found to have weakened or disappeared, and the above sounds appear when the high-pressure fuel pipe is connected, the cylinder connecting rod bearing or bolt Bolt failure.

The diesel generating set connecting rod bush is a wearing part, and the new one can be replaced normally. For a small number of repaired bushes, manual scraping, boring and other methods can be used for repair.

The crankshaft flywheel assembly is an important part of the diesel engine 14F. It is rotated by the thrust of the piston rod assembly and outputs power via the flywheel, and drives the valve train and other auxiliary devices.

The crankshaft is made of wear-resistant cast iron and its structure is divided into two types: integral type and combination type. The integral crankshaft is formed by forging a whole piece of steel, such as the 190-series diesel engine, single-cylinder diesel engine and a few medium-sized diesel engines. The combined crankshaft is manufactured separately from the crankshaft components and then assembled by connecting screws, such as the 135 series diesel engine and various large-scale diesel engines.

The crankshaft mainly consists of belt pulleys, front axles, cranks, roller bearings and output flanges, as shown in Figure 2-29. The crankshaft is the most important rotating part in a diesel engine and it converts the reciprocating motion of the piston into a rotary motion.