Selection and installation of diesel engine cylinder liner
Diesel engines mostly use thick-walled wet cylinder liners, which are sealed and installed in the cylinder block by the water blocking ring, and form a cooling water chamber with the inner wall of the cylinder. The inner surface of the cylinder liner is a component of the combustion chamber and is the place where the piston compresses the gas to do work. The outer surface of the cylinder liner is in contact with the cooling water for a long time, and is easily damaged by the cavitation and electrochemical corrosion; the inner surface is directly subjected to the high temperature, high pressure and corrosion of the gas, and the relative motion side thrust and the strong friction force of the piston assembly, Wear, scratches and fine cracks on the cylinder surface. Therefore, the cylinder liner is a wearing part. When the engine is overhauled, it is necessary to test the technical state of the cylinder liner and replace the unqualified cylinder liner in time.
1 cylinder replacement standard
(1) Observe the inner surface of the cylinder liner for signs of scratches, rust, etc. If it is defective, it will make the oil on the cylinder wall of the work not be cleaned, resulting in burning oil, which should be replaced.
(2) Put the new piston ring into the cylinder liner, use the piston to push the position of the first air ring to the top dead center, and observe the opening size. If the opening is above 1 mm, replace it; if the opening is 0.5~1.0 For mm, in order to extend the service life, the ring can be installed 180° offset.
(3) Observe whether there is crack in the cylinder liner. Generally, when the crack is generated at the top dead center, the position of the first air ring is broken and it should be replaced in the surrounding direction.
(4) If the cylinder sleeve wear exceeds the specified value, that is, the cylinder liner wear exceeds 0.3 mm or the ovality exceeds 0.15 mm, or the cylinder sleeve with severe eccentric wear should be replaced.
2 cylinder sleeve matching method
(1) When purchasing a new piece, the size code of the cylinder liner and the piston and piston ring must be the same. Only in this way can the cylinder sleeve and the piston have a standard matching clearance. For multi-cylinder engines, the size codes of all cylinder liners, pistons and piston rings must be the same. In addition, the weight difference of all cylinder piston sets should be within the specified range.
(2) According to the repair size, the milled sleeve is repaired. When the piston and piston ring are selected, the size standard must be consistent with the repaired size of the cylinder liner, and the weight difference of each cylinder piston group should be within the specified range.
(3) In order to ensure the assembly standard, the assembly clearance should be re-examined before the cylinder liner and piston are assembled. Firstly, the cylinder head gauge is used to measure the inner diameter of the cylinder liner (including roundness and cylindricity error), then the outer diameter micrometer is used to measure the piston skirt size, and finally the matching clearance between the two is calculated.
3 cylinder sleeve installation method
Improper installation of the engine cylinder sleeve may cause failures such as pulling the cylinder, early wear, exhausting smoke, water leakage, burning cylinder mats, crushing cylinder liners, and engine noise.
3.1 Installation of wet cylinder liner
Tractor engines and general agricultural diesel engine cylinder liners, mostly wet cylinder liners. The installation method is as follows:
(1) When installing the wet cylinder liner, the cylinder liner and the cylinder bore should be thoroughly cleaned first, especially the cleaning of the upper and lower support rings of the cylinder liner. If burrs, sharp corners and scratching are found, use a trowel to remove it and then sand it with a sanding cloth.
(2) Before installing the water resistance ring, the cylinder liner should be placed in the hole of the cylinder block for trial installation. The cylinder liner can be gently rotated in the hole of the cylinder block without any obvious shaking. The key point is that the cylinder sleeve shoulder should protrude from the cylinder plane 0. 06~0.15 mm, and the copper pad adjustment should be applied when it is insufficient. When padding is required, the pad should be placed on the cylinder liner, and then the water blocking ring should be installed so that it is placed on the upper end of the cylinder block hole. When the amount of protrusion is too large, the upper end of the cylinder liner should be repaired. 05毫米。 The height difference of the adjacent cylinder of the multi-cylinder engine, the maximum shall not exceed 0. 05 mm. When assembling, make sure that the upper end surface of the cylinder seat hole is clean and free of debris.
(3) Whenever the cylinder liner is pressed, the new water blocking ring should be used regardless of whether the cylinder liner is new or old. The gel of the water blocking ring should be soft and free of cracks. The size and size should meet the requirements of the original engine. It is best to use the original parts of the water blocking ring to ensure that the elastic recovery coefficient is greater than 85%, and can meet the technical requirements of not more than 15% of the compression at a pressure of 0.7 MPa. Only seals that meet this technical requirement can ensure that the diesel engine will not leak for a long time. Before installing the water stop, check the quality of the water blocking ring and smooth the burrs. It is found that water-blocking rings with defects such as aging, cracks, inelasticity, uneven thickness, too thick or too fine should be scrapped and cannot be installed.
(4) When the water blocking ring is assembled, there should be no distortion. If a kinking occurs, insert the cylindrical part of the screwdriver and smooth the smooth surface along the circle. Then apply a layer of lubricating oil or soapy water to the outer ring surface to assemble the cylinder.
(5) When the cylinder is set to the seat hole of the human cylinder, apply the average force of both hands to press twice. If you press the cylinder head, be careful to twist the nut evenly and symmetrically, and do not use a hammer. If it is found that the fit is too loose, the reason should be removed and installed after exclusion.
(6) After the cylinder is set, due to the certain tightness of the water blocking ring, the cylinder liner may be deformed. The inner diameter, roundness and cylindricity of the cylinder liner should be re-measured (not to exceed 0.03 to 0.04 mm). ), check whether the cylinder liner is deformed, check whether the cylinder liner is skewed, and check whether the height of the cylinder head of each cylinder liner of the multi-cylinder machine is consistent. The second step is to fill the water tank with a cooling water, preferably from 0.15 to 0.20 MP. The pressure was tested for 5 min of water pressure and it was observed whether there was water leakage at the assembly joint and reinstalled if any. When conditions permit, a running-in test is required.
3.2 Dry cylinder liner installation
(1) Select the cylinder liner. 005毫米。 The first inset of the standard size of the cylinder liner, the outer diameter of the surface roughness is not higher than Ra3. 2, the cylindricity does not exceed 0. 02 mm; if there is a reverse cone, the cylindricity does not exceed 0. 005 mm The roundness is not more than 0.05 mm, and the outer ring direction has a chamfer of 10×5.
(2) The installation of the dry cylinder liner is almost the same as the installation of the wet cylinder liner. The difference is that the outer diameter of the cylinder liner is required to be closely matched with the inner diameter of the cylinder seat bore. It should be cleaned during installation and must not be in the outer diameter of the cylinder liner and the cylinder block. The inner diameter of the seat hole is oiled to avoid affecting the uniform fit of the cylinder liner and the cylinder block. According to the outer diameter of the cylinder liner, the test cylinder is to be ensured that the surface roughness of the mounting hole is not higher than Ra3.2, and the appropriate pressure interference is left.
(3) Pressing the cylinder liner. Put the cylinder liner in the positive direction, press it with a press, or press it with other equipment. The pressure is 103 N. In order to ensure that the cylinder liner is pressed straight, the square ruler is used to measure the cylinder sleeve before pressing. When the cylinder liner is indeed perpendicular to the upper plane of the cylinder block, pressure is applied slowly. After the cylinder liner is pressed, it should be flush with the plane of the cylinder block.
(4) After pressing the cylinder liner, the cylinder block shall be subjected to hydrostatic test without leakage.