The Development Of Balance Axis System For 4-cylinder Engine

In some field Four-Cylinder diesel engines dominate obviously, which their height and width are corresponding loose, but length harshly, and power and torsion require higher. At the same time, the configuration of four-cylinder engine determine that it can not eliminate the influence of two order reciprocating inertial force by it's own balance. Double balanced shaft structure of four-cylinder diesel engine is two shafts with counterweight that set up within the engine, these two shafts rotate in double rotational speed to crank shaft and in the opposite direction. Counterweight of double balanced shaft makes engine to actualize dynamic equilibrium, that's because the periodic centrifugal force produced while rotating which just counteract two order reciprocating inertial force. Owing to balancing the engine vibration of inside caused by two order reciprocating inertial force, double balanced shaft configuration of engine has the following advantage:1, Reduce the vibration of the vehicle and increase the driven comfort. 2, Reduce the noise produced by vibration. 3, Improve the dependability of the engine and life of extension. Meanwhile, the balance configuration has some shortcomings too: 1, Increase the manufacturing cost. 2, Increase the height and width of engine .3, Balance configuration make power loss, increase the oil consumption and reduce the mechanical efficiency of the engine. In the case of balance essences of four-cylinder diesel engine, the concept of double balanced shaft can be divided into two big classes: A type of balance, it is a balanced assignation for second order reciprocating inertial force merely. It is a standard Lanchester prototype too. Namely two balanced shafts assign in the way of being symmetry to crankshaft central line and in the same height, which rotate in two times as much as that for engine rotational speed in the opposite direction. B type of balance, it gives consideration to second quantity in harmony of the balanced torsion while balancing second main vector of reciprocate inertial force. B type of balance keep symmetry tocrankshaft central line, vary height to assign. Namely two balanced shafts are fixed up symmetrically about the center line of crankshaft which rotate in opposite direction; the one that in the same direction with crankshaft in the higher position and the other one in the lower position, the difference in height of two balanced shafts is equal to the length of the connecting rod. As for arrangement of the balanced configuration, it can be divided into total length balance and not. 1) Total length balance: it is the balance configuration that disposing balanced shaft within the range of total length of the engine and assigning necessary uneven balanced configuration. It mostly designs four-cylinder machine types with balanced configuration in prototype design to adopt the total length balance models. 2) Not total length balance: It is not the total length balance that the balance except the total length balance is referred to as. According to the driving way of the configuration, it can be divided into both of a gear and a sprocket. 1) Gear drive, which the double balanced shaft is driven by additional gear of crankshaft.2) Sprocket drive, which the double balanced shaft is driven by additional sprocket of crank shaft drive the roller chain. In 2001, Yuchai cooperated with ICE research of Shanghai, they developed the balance system of double shafts which driven by gear. This set of balanced configuration is a balanced assignation only for two order reciprocating inertial force (main vector). It is a primitive, traditional, basic type adopted so far extensively, it is a standard Lanchester prototype too. Namely two balanced shafts assignation in the way of symmetry to crankshaft central line and in the same height, which rotate in two times as much as that for engine rotational speed in the opposite direction. The main characteristic of the configuration is: Install a relatively gear on the crank journal of the last gear, drive one balanced shaft(initiative balanced shaft)through the additional gear, initiative balanced shaft equip with one driven gear and a initiative gear, the driven gear is urged by additional gear on the crankshaft, but the initiative gear is used for driving another balanced shaft (passive balanced shaft), passive balanced shaft equip with passive gear too, it is used for gearing the initiative gear of the initiative shaft. The whole set of balance system adopt total lengthbalance, hanging it in the engine housing underpart, two balanced shafts are symmetrical about cylinder central line and in the same height. The rotational speed of balanced shaft is two times as much as that of for crankshaft. The advantage of this scheme is little change to original machine, the related producer can choose the balanced configuration according to the needs of reality. But this scheme has its shortage, it is difficult to guarantee relative position between meshing gears in the course of processing and assembling, so it is worse than direct drive gear transmission in dependability and noise. The test of YC4112T diesel engine after installing balanced configuration indicates that the balanced configuration can reduce vibration of engine. The vibration intensity is lowered to 17.4mm/s from original 48.9mm/s, reach better, especially near 76Hz the vibration frequency has dropped by nearly 70%. The frequency of two order reciprocating inertial force is twice of the rotational speed of an engine. So when the rotational speed of the engine is 2300r/min, the frequency of two order reciprocating inertial force is 76Hz. Therefore double balanced configuration is very effectual to balance the twoorder reciprocating inertial force. After installing balanced configuration, fuel consumption rise about 2-3%, power dropped by 3% when the rotational speed of the engine is higher than 2000r/min. The change of oil consumption and power are not obvious when smaller than 2000r/min. But within the range of rotational speed of the engine entirely, the exhaust temperature has rising in various degree which indicates that there are power loss on balanced configuration within the range of whole rotational speed. For the thesis about double balanced shaft of YC4112T, this paper do the following aspects work: Investigate and analyses to the similar domestic and international products in the domestic market. Analyses about the vibration characteristic and balance of various kinds of internal-combustion engines with different cylinder diameters on the basis of balanced theory. Analyses about the principle and the way of assign of the balanced configuration in four-cylinder engine. Make three schemes on the YC4112T original model, selectone of them kind as implementing scheme, develop a set of balanced system of double shafts which is compact in configuration and can establish one's own system. Have compared with the test on a test-bed.