2022-01-07 News Views 998
The piston connecting rod group is the transmission part of the engine. It transmits the pressure generated by combustion gas to the crankshaft, which rotates and outputs power. Piston connecting rod group is mainly composed of piston, piston ring, piston pin and connecting rod. Piston connecting rod group working conditions are bad, piston, piston ring, connecting rod are wearing parts, maintenance replacement disassembly is inevitable, correct assembly of diesel engine performance and service life is very important. If not enough attention, in the disassembly process will cause further damage and deformation of parts, and even irreparable.
1. Key points of assembly of piston connecting rod group
(1) Before assembling the piston and connecting rod group, note that the piston model should be consistent with the engine model. An engine should choose the same manufacturer, the same quality level of piston, connecting rod, piston pin. Generally the same diesel engine piston quality difference can not exceed 8g, connecting rod quality difference can not exceed 40 g, piston connecting rod group quality difference can not exceed 50 g. Otherwise it will cause engine vibration, deflagration and lead to damage.
(2) when assembling, pay attention to the mark on the connecting rod. LR4105T diesel engine, the connecting rod marked with "YT" faces the front end of the diesel engine, and the arrow direction on the top of the piston is the same; Guangxi Yuchai YC6105QC diesel connecting rod 45. The split surface is on the same side with the fuel injection pump or injector, and the direction of the split surface of the connecting rod 450 should be consistent with the position of the valve pit on the top surface of the piston; The matching mark of the serial number or head cover of the first drag (Luoyang) 4125A connecting rod is toward the fuel injection pump or injector side, and the matching mark of the connecting rod serial number or head cover is on the same side as the pit of the top vortex of the piston; The serial number of the connecting rod or the matching mark of the head cover (or the guide groove of the piston top) is on the opposite side of the camshaft, and the side of the connecting rod with the matching number must be on the same side as the guide groove of the piston top.
(3) before installation, the piston should be heated in the engine oil at 80℃ for 10 min, and the pin hole should be heated and enlarged, and then the piston pin should be installed. When assembling the piston and connecting rod, attention should be paid to the installation direction of the connecting rod and piston. 95 series diesel engines, the opening of the big end of the connecting rod is opposite to the direction of the guide port of the piston top vortex pit or spherical pit, and the oil hole of the connecting rod is upward.
(4) before the piston and rod assembly into the piston pin, piston pin surface coated with lubricating oil, the piston pin hole not put one end of the spring with the hand pushing away quickly, through the connecting rod bushing, and make the piston top combustion chamber top shovel type pit shape with small head of the oil hole in the same direction, ensure the oil into the bushing, lubrication sleeve and the piston pin. After installing the piston pin, the piston and connecting rod should rotate flexibly, not loose and loose, and no sense of block.
2 Piston connecting rod set is fitted into cylinder
(1) Cleaning. Clean all the parts to be installed, and evenly coat the surface where the parts to be installed move with oil.
(2) Check the deviation cylinder. The cylinder liner and crankshaft have been installed on the side of the body on the work table, the bottom of the wooden square pad. One by one, install the piston connecting rod group without piston ring onto the corresponding connecting rod. The tile is installed in the cylinder according to the original cylinder number, and the installation direction is correct: the top of the piston with a guide groove to the injector side, the top of the piston with an arrow to the front of the body; The lower tile is mounted on the corresponding connecting rod cover, and is mounted on the connecting rod journal together with the big end of the connecting rod and the upper tile, with the connecting rod matching mark or tile positioning slot on the same side. Tighten the connecting rod nut according to the specified torque (4125A4 186 ~ 206 N·m, C A6102 J166 ~ 73.5 N·m) by several times.
3 Install piston ring
(1) The piston ring installation is easy to break, so it is best to install the piston ring using special tools piston ring clamp. The use of piston ring calipers can also prevent the piston surface from being strained during assembly.
(2) The installation sequence of the piston ring is from bottom to top, that is, first install the oil ring, and then install the gas ring. Air ring is also from bottom to top. Do not install wrong piston rings with directional requirements. First load chrome plated barrel surface ring or chrome plated rectangular flat ring. The second and third conical ring, if the inner edge of the twisted ring with grooves, the grooves should be upward; If the outer edge has grooves, install it downward. With "TOP" or other marks on the side up, do not reverse, otherwise it will burn oil, increase the diesel engine smoke. Unmarked piston ring and oil ring are fitted neck and neck.
(3) When installing the piston ring, attention should be paid to stagger each ring opening 120°, the opening of the first ring is facing the exhaust pipe side, and the counterpart of the oil ring spring is placed on the opposite side of the oil ring opening.
4 The piston connecting rod group is assembled to the cylinder liner
(1) Cleaning. Clean all parts to be installed, evenly coated with oil. Turn the crankshaft to bring the corresponding connecting rod journal to the BDC position. Put the piston connecting rod group in the correct position and direction so that all the connecting rod and 2/3 of the piston are loaded into the cylinder.
(2) arrange the opening direction of piston ring. Stagger the opening direction of the first and second gas rings 180°, and the opening direction should avoid the piston pin and the main side pressure direction (make the opening direction located at the Angle of 45° between the pin shaft and the side pressure direction). Stagger the opening direction of the oil ring by 90°. If there is a third gas ring, its opening is staggered 180° from the opening of the oil ring. Press the piston ring with the piston ring clamp and push the piston into the cylinder with a wooden stick or hand hammer handle.
(3) assembly. Connecting rod tile cover pull the big end of the connecting rod with both hands, the big end and the upper tile against the journal of the connecting rod. The connecting rod tile cover and the lower tile are buckled on the connecting rod journal in the correct direction, and the connecting rod end and the upper tile are mounted together.
(4) Tighten the connecting rod nut. Tighten the connecting rod nut by turns according to the specified torque, and align the pin hole with the nut groove. If it is not correct, replace the nut or grind off a little nut plane. Do not use the method of increasing or decreasing torque to check the pin hole. Hammer the tile cover of the connecting rod forward and back along the crankshaft. The connecting rod should be able to move back and forth. Turn the crankshaft one or two times to make sure there is no problem before installing the next piston connecting rod in the same way.
(5) After the assembly of all piston connecting rods is completed, turn the crankshaft for several turns, and its rotational resistance should be normal. Ensure that there is no problem, then use the appropriate cotter pin to lock the connecting rod nuts in the same direction.