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Detection and correction of the bending and torsion deformation of the engine connecting rod
  • Automotive

In the work of connecting rod, due to the greater force, the bending, twisting, bending and twisting of the rod body are easy to occur. The bending or distortion of the connecting rod will make the piston skew in the cylinder, causing the eccentric wear of the piston and cylinder and connecting rod bearing, the leakage of gas between the piston group and the cylinder, and the excessive oil consumption in the engine, the low compression force of the cylinder, the lack of power, and the large negative pressure of the crankcase. There are different axes on the center line of the two piston pin holes on the piston, the crankshaft is deformed, the two main necks are different axes, and the cylinder sleeve is worn in a serious way. Therefore, it is necessary to detect and correct the connecting rod in time. The causes of the bending deformation of 1. connecting rods (1) the reasons for their use. When the engine is running at an over speed, low speed or over load operation or oil supply time is too early, it often leads to the throttle, which easily causes the deformation of the connecting rod. Even in normal operation, the connecting rod is prone to fatigue deformation due to its strong compression and stretching. (2) mechanical accidents. Accidents in engine operation, such as flying cars, burning tiles, holding shaft, piston swelling and failure, often lead to deformation of connecting rod. (3) reasons for repair and assembly. The clearance between the cylinder sleeve and the piston is too small, so that the piston is stuck in the cylinder sleeve after being heated, and the connecting rod is broken or bent. During the repair process, such as the it connecting rod tile, the connecting rod is clamped on the vise to tighten or unscrew the connecting rod nut, which is also easy to cause the deformation of the connecting rod. When installing, the central line of the piston pin is not parallel to the central line of the crankshaft connecting rod journal, and the connecting rod is prone to fatigue bending or even cracking. The detection of bending and torsion of 2. link (L) can be done by connecting rod tester. The following methods are as follows: (1) before testing, the expansion and positioning mandrel, the inspection plate and the size end hole of the connecting rod are cleaned. The large end hole of the connecting rod is set on the bulging positioning core shaft, and the connecting rod is placed vertically to make the bulging positioning core shaft open and the connecting rod fixed on the positioning core axis. The test core axis is inserted in the small end hole of the connecting rod, and the "three point gauge" V groove with the V shaped block is contacted with the test core shaft, and the "three point gauge" is gently moved to contact the test point with the test plate. (4) using the feeler gauge to check the clearance between the measuring point and the test plate, the bending and distortion of the connecting rod can be judged and detected. (2) the judgement of the test results: (1) if the three points of the three point gauge are contacted with the test plate, it is shown that the connecting rod has no bending and distortion. If the measuring point is in contact with the test plate, the following two points are not in contact with the flat plate, and the gap is equal to the flat plate; or the following two points are in contact with the flat plate, and the upper test point does not contact the plate. It shows that the connecting rod produces the bending deformation and the gap between the measuring point and the plate is measured by the tape measure, that is, the connecting rod is in the length of 100 mm. The bending deformation value. 3. If only one point is in contact with a flat plate, and the gap between the measuring point and the plate is equal to half the gap between the other and the flat plate, the gap between the lower measuring point and the plate is the distortion value of the connecting rod at the length of 100 mm. (4) if only one point is contacted with a flat plate, the gap between the upper test point and the plate is not equal to half of the gap between the other and the flat plate. It shows that the connecting rod has both bending and distortion, and the gap between the measuring point and the plate is the distortion of the connecting rod in the length of 100 mm, the gap between the measuring point and the plate and the lower measuring point. Half of the gap between the plates is the bending deformation of the connecting rod on the length of 100 mm. When measuring the positive and negative two sides of the connecting rod, it is found that when the distance between the small end of the connecting rod and the test plate is different, the connecting rod has double bending, and the difference between the two measurement values is the double bending deformation. Correction of bending and torsion of 3. link (1) when the bending degree of the connecting rod is greater than the required accuracy, it can be corrected on the bending corrector. Correction procedure: (1) when testing the bending degree, remember where the bending direction is, and use chalk to mark the bending of the connecting rod. 2. According to the length of the connecting rod and the direction of the bending position, the pad is adjusted to an appropriate position. 3. Put the connecting rod on the pad firmly and safely, and gently rotate the handle to press the pad tightly on the connecting rod. Release the connecting rod from the handle and check it on the straightness tester. If it does not meet the accuracy requirement, it must be repeated until the calibration requirement is reached. (2) when the torsion degree of the connecting rod is greater than the required accuracy, it can be calibrated by the torsion corrector. Correction procedure: (1) when checking the twist degree of the connecting rod, we should remember the direction and position of the twist, and use chalk to make a mark for the correction of the twist of the connecting rod. (2) put the big end of the connecting rod smoothly and fixed in the adjustable pin shaft on the straightness tester (or padded on the soft metal pad, clamped on the vise), rotating the handle of the corrector, opening the arm and loosening the six angle nut, generally making the distance between the two grabbing blocks 100~150 mm, and then tightening the six horns nut, so that the grabbing block presses the connecting rod wing. Edge. 3. The rotating handle makes the arm lever compress the flange and correct. (4) reversing the handle, loosening the tightening screw, detaching from the connecting rod, taking the connecting rod down, and checking it on the straightness tester, and repeating the correction if it does not meet the precision requirements. (3) when the connecting rod is checked by a straightness tester, when the bending and distortion exist at the same time, the distortion is usually corrected first, then the unidirectional bending or two way bending deformation is corrected. At normal temperature, the "elastic" and "aftereffect" phenomena will occur when the connecting rod is corrected. That is to say, after unloading the load, the connecting rod has the tendency of restoring the deformation to its original shape. Therefore, when correcting the connecting rod with large bending and distortion, the correction must be carried out after correction. The corrected connecting rod is heated to 400~450 C, and the heat preservation is 0.5 to 1 h to eliminate the residual stress produced in the connecting rod. After the stabilization, a check is carried out. The correction load can be maintained for a certain time when correcting the bending and twisting of smaller connecting rods. For example, if the deformation of the connecting rod is too large, it should be heated evenly to 450~600 C at the correct location, while hot correction, and then use asbestos cloth to wrap it slowly.