| The size of the fitting clearance depends on the design of connecting rod bushings aperture. If the clearance is too small, piston pin activities will be not flexible, and even killed. But is easy to produce taps and the noise with a large clearance, and it also can cause the bushing damaged or a deformation of connecting rod bending and twisting. Appropriate clearances can form oil film and plenty bearing pressure, this play a role about lubricating bearings and carrying weight. After the bushing was pressed into the connecting rod small end, it will be affected by radial stress, and a certain amount of shrinkage deformation will be produced in the hole. It will make changed on the fitting clearance between bushings hole and piston pin. The result is that it changed the original clearance, and even cause a difficult assembly. Only to reaming or repair blow can get the required hole tolerances and solve the assembly inconvenient questions. In order to free the scraped program, and improve work efficiency, this topic using elastic deformation theory to proceed theoretical analysis and fem simulation analysis about the shrinkage deformation condition of the bushings aperture. The mainly research contents of this paper are as follows:1. On the basis of the theory of elastic deformation, the Aperture shrinkage under Press fits over surplus is calculated through theory. The actual aperture dimensions tolerance zone has been fixed, Aperture shrinkage and work clearance are analyzed and calculated under work surplus.2. The influence on some related parameters of the aperture contraction such as material elastic modulus, structure size of bushing and the magnitude of interference between connecting rod small head and bushing are researched.3. The situation of Aperture shrinkage are analyzed by using the finite element software simulation ANSYS. These situations are made by comparing cylindrical bushing with ladder model bushing, then bimetal wrapped bushing and integral tin bronze bushing are also be compared.4. Consider the structure of the oil groove may have an certain influence on the bushings, oil groove what impact on bushing deformation are analyzed by using the finite element contact simulation. Aperture shrinkage deformation are compared between the bushing with oil groove and the one without the oil groove. Then the influence about the width and the relative depth of the oil groove to the busing shrinkage deformation was researched.5. Load bearing status of connecting rod bushing is analyzed. By simulation analysis, the strain and stress distribution of bushing in pre-tightening, stretching and compression working conditions are concluded. By thermal-structure coupling analysis, the strain and stress state of bushing under working temperature are studied.The above research shows that the main factors what impact on aperture shrinkage of connecting rod bushing are magnitude of interference under Press fit, material characteristics, structure size. When the magnitude of interference is established, a cylinder type tin bronze bushing, of all bushings, has a good shrinkage deformation under work temperature. Peripheral oil groove has little influence on bushing contraction, but the influence on the lubrication conditions can not be ignored.
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