Posted 12 Mar 2011 16:46
The strength of a heavy-duty truck CPB14RHH Japan, the engine model Nissan NE6, traveling 300,000 kilometers caused when the oil cylinder rod bearing the second ablation, the detector detecting the crankshaft no scars, repair the engine crankshaft to increase after correction . When traveling around 20,000 kilometers, the crankshaft connecting rod journal in the third and fourth channel cylinder shaft fracture at the neck joint section, we consider the poor roads, after the crankshaft can not afford to increase the rated load, while the trucks are often rated load work overload caused by the goods even. So, to replace a new crankshaft, driving over 20,000 km in the second cylinder after the crankshaft and connecting rod journal associated with the third section of the spindle at the neck fracture, the accident caused our attention. A fractured crankshaft crankshaft breaking for the reasons summarized in the following general points: overload traffic, the engine often in a state of high-speed or overdrive; high speed, often slam the brakes; poor road conditions, driver improper operation; crankshaft material inequality, poor fatigue resistance; crankshaft itself is invisible injury; oil quality is poor, there is the phenomenon of holding tile; main bearing loose; main bearing bore distortion analysis and detection of 2.1 2 ask crankshaft fracture under the above reasons, we with the driver and assistant conversation, careful to understand the use of the car, the driver reflects the engine after the repair the car, the engine sound powerful but small, not black smoke, fuel consumption is normal. Recently on the road in the city are run speed fast, there have been no braking phenomenon, the driver is the company opened 20 years old car driver, driving experience. And as far as I can prove that operation of the company over recent chats true. So you can rule out the "overload driving, braking, poor road conditions" and other reasons. 2.2 In addition to the detection of "crankshaft material inequality, poor fatigue resistance" temporarily can not be detected, the engine crankshaft fracture anatomy junction and from the observation, no old wounds; connecting rod bearing and rod bearing surfaces with normal wear and tear, and no hold tile phenomenon; remove main bearing tile, tile installed on the main bearing cap, tighten the bolt force required, with the dial indicator to measure the diameter, the deviation of less than 0.01mm, but the third, four holes on the seat a little scratch traces; then remove the main bearing cap tile, according to oil path hole basis, with steel tape measure deviation of seven holes, found three or four holes and other holes than a difference of 0.5mm. Thus, the crankshaft socket fracture due to deformation caused by scratching and socket. 3, has been driving the car repair and processing nearly 40 million kilometers, taking into account the retirement of close to, if the replacement of a new block, from an economic point of view uneconomical. But from the perspective of the overall performance of the car, the car is still value in use. We therefore adopted the machining method: buy a new crankshaft, cylinder block main bearing bore a large hole 2mm, in accordance with the increase of the crankshaft socket 2mm, 2mm thick reconstituted a main bearing, the diameter of standard parts processing by the crankshaft . The engine after the repair has traveled over 40,000 kilometers, from the sound of the engine, smoke-color, power, fuel consumption and other aspects of evaluation, the car performance is normal.