曲柄连杆 外文翻译 - 图文(3)

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otherwise invisible small cracks which would cause the rod to fail under stress. In addition, great care is taken to torque the con rod bolts to the exact value specified; often these bolts must be replaced rather than reused. The big end of the rod is fabricated as a unit and cut or cracked in two to establish precision fit around the big end bearing shell. Therefore, the big end \are not interchangeable between con rods, and when rebuilding an engine, care must be taken to ensure that the caps of the different con rods are not mixed up. Both the con rod and its bearing cap are usually embossed with the corresponding position number in the engine block. Recent engines such as the Ford 4.6 liter engine and the Chrysler 2.0 liter engine, have connecting rods made using powder metallurgy, which allows more precise control of size and weight with less machining and less excess mass to be machined off for balancing. The cap is then separated from the rod by a fracturing process, which results in an uneven mating surface due to the grain of the powdered metal. This ensures that upon reassembly, the cap will be perfectly positioned with respect to the rod, compared to the minor misalignments which can occur if the mating surfaces are both flat. A major source of engine wear is the sideways force exerted on the piston through the con rod by the crankshaft, which typically wears the cylinder into an oval cross-section rather than circular, making it impossible for piston rings to correctly seal against the cylinder walls. Geometrically, it can be seen that longer con rods will reduce the amount of this sideways force, and therefore lead to longer engine life. However, for a given engine block, the sum of the length of the con rod plus the piston stroke is a fixed number, determined by the fixed distance between crankshaft axis and the top of the cylinder block where the cylinder head fastens; thus, for a given cylinder block longer stroke, giving greater engine displacement and power, requires a shorter connecting rod (or a piston with smaller compression height), resulting in accelerated cylinder wear. Compound rods Many-cylinder multi-bank engines such as a V-12 layout have little space available for that many connecting rod journals on a limited length of crankshaft. This is a difficult compromise to solve and its consequence has often led to engines being regarded as failures. The simplest solution, almost universal in road car engines, is to use simple rods. This requires the rod bearings to be narrower, increasing bearing load and the risk of failure in a high-performance engine. This also means the opposing cylinders are not exactly in line with each other. In certain types of engine, the master rod carries one or more ring pins to which arebolted the much smaller big ends of slave rods on other cylinders. Radial engines typically have a master rod for one cylinder and slave rods for all the other cylinders in the same bank. Certain designs of V engines use a master/slave rod for each pair of opposite cylinders. A drawback of this is that the stroke of the subsidiary rod is slightly shorter than the master, which increases vibration in a vee engine. The usual solution for high-performance aero-engines is a \connecting rod. One rod is split in two at the big end and the other is thinned to fit into this fork. The journal is still shared between cylinders. The Rolls-Royce Merlin used this style.

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Crank linkage of the type and characteristics The use of the internal combustion engine crank linkage of many types, according to kinematics perspective can be divided into three categories, namely: Heart crank linkage, the eccentric crank linkage and the main vice-link crank linkage. Centre crank linkage is characterized by the cylinder through the centerline of the crankshaft rotation centre and perpendicular to the axis of rotation of the crank. This type of linkage in the internal combustion engine crank in the most widely used. The single-engine general, tied for linkage with the use of the V-shaped chaxing link the internal combustion engine, and the home of the piston internal combustion engine crank linkage fall into this category. Eccentric crank linkage is characterized by vertical cylinder centerline of the crankshaft rotating in the center, but not by crankshaft rotary centre, the cylinder centerline distance between the crankshaft with a rotary axis offset e. This crank linkage institutions can reduce the swelling in the itinerary of the piston and cylinder intramural largest lateral pressure so that the pistons in the expansion programme and pressure reduction programme in the cylinder wall at the role of lateral pressure on both sides of the relatively uniform size. Vice-link the main crank linkage is characterized by: the internal combustion engine cylinder with a main link, the other out vice-link cylinder used, these are not direct link to the bottom of the crank pins, but on sale through the deputy link with in the main link of the big heads, formed a \movement, such institutions also sometimes referred to as \stalk linkage \linkage in the joint, a crank can put a few of connecting rod and piston, This structure will shorten the length of the internal combustion engine, compact and widely used in high-power locomotives used tanks and V-shaped internal combustion engine. Boring In machining, boring is the process of enlarging a hole that has already been drilled (or cast), by means of a single-point cutting tool (or of a boring head containing several such tools), for example as in boring a cannon barrel. Boring is used to achieve greater accuracy of the diameter of a hole, and can be used to cut a tapered hole. The term boring is also sometimes used for drilling a hole. Machine Boring The boring process can be carried out on a lathe for smaller operations, but for larger produ …… 此处隐藏：5755字，全部文档内容请下载后查看。喜欢就下载吧 ……