What are the 3 common forms of cylinder block damage?

Cracks, abrasions, deformations, and threaded slip buckles, etc.

There are three main forms of damage to the cylinder block: cracks, deformation and wear.

1.Crack. The common cylinder block crack phenomenon and the main causes of cracks are: crankshaft.

Vibration occurs when rotating at high speed, and cracks occur in the weak parts of the cylinder block; When the engine is in a high temperature state, a large amount of cold water is suddenly added, or the heat dissipation is poor due to excessive scale accumulation, which causes cracks in the waterway wall; Antifreeze is not filled in winter and cold regions.

causing waterways to freeze and crack; When the cylinder block with cylinder liner is inlaid with cylinder liners, the interference amount is too large or the press-fitting process is improper, resulting in local cracks in the cylinder; When assembling cylinder bolts, the tightening torque is too large, or the interference amount is too large when the sleeve repairs the damaged threaded hole, etc., resulting in cracks in the original threaded hole.

Cracks in the cylinder block will cause water, oil and air leakage, affect the operation of the engine cooling and lubrication system, and even make the cylinder tightness worse. The parts of the cylinder block that are prone to cracks are often related to their structure, and the parts that are prone to cracks in different forms of engines have different rules, and attention should be paid to observation and inspection.

2.Deformation. It is common for cylinder blocks to deform during use.

The deformation of the cylinder block disrupted the correct geometry of the parts, affecting the assembly quality and working capacity of the engine. For example, the flatness error of the joint surface of the cylinder block and the cylinder head exceeds the limit, which will cause the cylinder seal to be not tight, air leakage, water leakage, and even gas flushing out the cylinder gasket, which will seriously affect the assembly quality of the engine.

The common deformation phenomena and causes of cylinder block are: due to excessive or uneven torque when disassembling bolts, or not tightening in order, and disassembling the cylinder head at high temperature, etc., the joint plane of the cylinder block and the cylinder head will be warped and deformed; The bulge of the upper and lower planes of the cylinder block around the threaded orifice is usually caused by excessive bolt tightening during assembly, or the threaded hole is not cleaned during assembly.

In addition, the cylinder block is manufactured due to aging treatment.

Insufficient internal stress of the part.

Large and uneven internal stresses, or internal stresses formed over long-term use, can also cause deformation of parts.

3.Wear and tear. The size and shape of the cylinder will change over time.

There are many factors that can cause the technical condition of an engine to deteriorate, but the degree of wear and tear of the cylinder is one of the important criteria for measuring whether the engine needs to be overhauled. Because the cylinder wear will directly cause the gas pressure to drop, so that the engine power and economy will be worse.

Cylinder wear is characterized by uneven wear. Specifically, the cylinder is worn along the working surface in the piston ring motion area in an irregular conical shape, and the large part of the wear is the cylinder wall corresponding to the first piston ring when the piston is at the top dead center position. The reason for cylinder wear is high temperature, high pressure, alternating load, and the piston and piston rings reciprocating in the cylinder at high speed.

The wear and tear of the engine cylinder and the cylinder head is mainly deformation, rupture, thread damage, etc., after the analysis and processing of a large number of measured data, it is known that the cylinder of the engine has different degrees of deformation, and its deformation has a certain law.

The main reasons for the deformation are that the casting molding is not sufficiently and effectively treated to eliminate its residual stress, and the high operating temperature and the yield limit of the material decreases. The deformation of the cylinder head is common, which is mainly due to the action of high temperature and high pressure gas, the tightening procedure and tightening torque of the cylinder head do not meet the requirements, and the improper placement of the cylinder head after dismantling the hot car.

It has been proved in practice that the deformation of the cylinder block is mainly manifested in the flatness error of the upper and lower planes, the hole axiality error of the crankshaft spindle seat hole, and the perpendicularity error of the cylinder axis and the axis of the crankshaft main bearing housing hole.

And regardless of the old or new cylinder block, the deformation of the upper plane has a certain regularity, that is, whether the longitudinal or transverse cylinder block, it is high at both ends (sides) and low in the middle. The deformation of the cylinder head is also often high at both ends (sides) of the lower plane and low in the middle.

Common Injuries to Cylinder Blocks:

1. Stomatae. Porosity is often the most common defect in cylinder block castings and often accounts for the first batch of casting scrap. The pores of the cylinder block are mostly found on the outer surface corresponding to the water jacket area of the upper surface, such as the bottom of the outlet needle or the raised ribs, and the inner surface of the cylinder barrel after machining.

In severe cases, due to the large gas generation of the core and the failure to fully exhaust, the upper surface will be choked, resulting in large areas of holes and irregular sand holes;

2. Trachoma. Sand hole is also a common lack of lease depression in cylinder block castings, which is mostly seen on the upper surface of the casting, and is also exposed on the inner surface of the cylinder barrel after processing;

3. Take the blind omen vein. Usually on the inner surface of the casting or the hot joint part, such as in the water jacket cavity of the cylinder block and cylinder head, or in the inlet and exhaust duct, due to the action of high-temperature molten iron during pouring, the phase transformation and expansion of the silica sand in the sand core causes cracks on the surface of the sand core, and the liquid metal penetrates into it, resulting in the formation of flying-like convex defects in the casting, that is, veins.

Common Injuries to the Cylinder Head:

1. Deformation. The warping deformation of the bottom plane of the cylinder head is often caused by improper disassembly and assembly, which will cause the cylinder to be tightly sealed and cause air leakage and water leakage. The warpage of the joint plane of the cylinder head can be measured with a ruler and a gauge;

2. Cracks. Cracks in the cylinder head caused by poor heat dissipation or uneven heat load, resulting in large thermal stress, generally appear between the intake and exhaust valve seat rings and on the surface of the vortex chamber. It will cause the phenomenon of gas-water channeling between the high-temperature and high-pressure gas in the combustion chamber and the cooling water;

3. Corrosion. Due to the excessive impurities contained in the cooling water, the cylinder head waterway hole will be gradually damaged and perforated through electrochemical corrosion, which will cause the cooling water to enter the combustion chamber and other adverse consequences.

The main losses of the cylinder block and cylinder head are: warping and deformation of the upper and lower planes of the cylinder block, cracks of the cylinder block and cylinder head, wear of the cylinder, damage to the threaded hole on the cylinder block and corrosion at the edge of the waterway hole.

Warping deformation of the upper and lower planes of the cylinder block, cracks of the cylinder block and cylinder head, wear of the cylinder, damage to the threaded holes on the cylinder block.

Check on the specific **.

1. The wear of the piston seal, which is the most common and the cause of air leakage.

2. The load and installation direction are not concentric with the piston rod, resulting in damage to the front end sealing ring and wear of the cylindrical surface of the front end of the piston rod.

3. The piston seal is excessively worn, or the cylinder barrel is deformed, causing the piston to directly rub against the inner wall of the cylinder barrel, and the inner wall will be seriously scratched, which is common on the large cylinder.

4. Too much dust and moisture from the outside world is brought into the cylinder by the piston rod, resulting in the wear of the front sealing ring and the cylindrical surface of the piston rod, which is common in harsh environments.

5. Mechanical damage caused by external forces, such as impact, excessive load, too much impact force, etc.

Except for the seal, which can be replaced, all other damage is not repairable.

It is recommended that you go to China Machinery Network to check.

The degree of wear and tear of the cylinder has the greatest impact on the dynamics of the car. The wear of the cylinder increases the gap between the piston and the piston ring, which reduces the pressure of the cylinder when compressed, resulting in a decrease in engine dynamics. There are many reasons for cylinder wear, mainly poor lubrication, mechanical wear, acid corrosion and abrasive wear.

During the use of the cylinder, its surface forms uneven wear in the area where the piston ring moves. Grinding into a large cone shape along the axis of the cylinder, the most worn part is the cylinder wall corresponding to the first piston ring when the piston is at the top dead center position.

The piston rings do not touch the upper mouth, and there is almost no wear to form a step. The cylinder is also worn unevenly in the circumferential direction, forming an irregular oval shape, and the maximum radial wear zone is usually close to the opposite side of the intake valve.

How, is the answer satisfactory?

The law of normal wear and tear of the cylinder is: large at the top and small at the bottom; large horizontal and longitudinal; Large on the intake valve side and small on the exhaust valve side; The cylinders at both ends are large and the middle cylinders are small.

The big regret talks about the damage of some cylinder head blocking cracks, Biheng bump, can be used ().

a.Screw filling method.

b.Welding method.

c.Sintering method.

d.Bonding method.

Correct answer: d